
==== Front
Can J Respir Ther
Can J Respir Ther
3251
Canadian Journal of Respiratory Therapy: CJRT = Revue Canadienne de la Thérapie Respiratoire : RCTR
1205-9838
2368-6820
Canadian Society of Respiratory Therapists Website: Canadian Journal of Respiratory Therapy

38084109
90653
10.29390/001c.90653
Research Article
A cross-sectional survey on the effects of ambient temperature and humidity on health outcomes in individuals with chronic respiratory disease
https://orcid.org/0009-0005-1333-5752
Mekhuri Samantha 1
https://orcid.org/0000-0001-5693-3182
Quach Shirley 2 3
https://orcid.org/0000-0001-8608-0889
Barakat Caroline 1
https://orcid.org/0000-0001-7616-5344
Sun Winnie 1 4
https://orcid.org/0000-0001-5323-9638
Nonoyama Mika L 1 2
1 Faculty of Health Sciences Ontario Tech University
2 Respiratory Therapy Department & Child Health Evaluative Sciences Hospital for Sick Children https://ror.org/057q4rt57
3 School of Rehabilitation Science McMaster University https://ror.org/02fa3aq29
4 dvancement for Dementia Care Centre (ADCC) Ontario Shores Centre for Mental Health Sciences https://ror.org/04mcqge53
Corresponding author: Mika Nonoyama RRT, PhD (corresponding) Faculty of Health Sciences Ontario Tech University 2000 Simcoe St N Oshawa, ON L1G 0C5 Canada Telephone: 905-721-8668 x5329 Fax: 905-721-3178 mika.nonoyama@sickkids.ca
8 12 2023
2023
59 256269
18 5 2023
20 11 2023
https://creativecommons.org/licenses/by-nc/4.0/ This is an open access article distributed under the terms of the Creative Commons Attribution-NonCommercial License (4.0) which permits non-commercial use, distribution, and reproduction in any medium, provided the original author and source are credited.

Rationale

Extremes of temperature and humidity are associated with adverse respiratory symptoms, reduced lung function, and increased exacerbations among individuals living with chronic obstructive pulmonary disease (COPD).

Objectives

To describe the reported effects of temperature and humidity extremes on the health outcomes, health status and physical activity (PA) in individuals living with COPD.

Methods

A cross-sectional self-reported survey collected the effects on health status (COPD Assessment Test [CAT]), PA, and health outcomes in 1) moderate/ideal (14 to 21°C, 30 to 50% relative humidity [RH]), 2) hot and humid (≥ 25°C, > 50% RH) and 3) cold and dry (≤ 5°C, < 30% RH) weather conditions. Participants were ≥ 40 years old with COPD or related chronic respiratory diseases (e.g., asthma, sleep apnea, interstitial lung disease, lung cancer) and residing in Canada for ≥ 1 year. Negative responders to weather extremes were a priori defined as having a change of ≥ 2 points in the CAT.

Main Results

Thirty-six participants responded; the mean age (SD) was 65 (11) years, and 23 (64%) were females. Compared to ideal conditions, 23 (66%) and 24 (69%) were negatively affected by cold/dry and hot/humid weather, respectively. Health status was significantly lower, and PA amount and difficulty level were reduced in hot/humid and cold/dry conditions compared with ideal conditions. The number of exacerbations in hot/humid was significantly higher compared to ideal conditions.

Conclusions

More participants were negatively affected by extremes of weather: health status worsened, PA decreased, and frequency of exacerbations was higher compared to ideal. Future prospective studies should directly and objectively investigate different combinations of extreme temperature and humidity levels on symptoms and PA to understand their long-term health outcomes.

Chronic Obstructive Pulmonary Disease
temperature
humidity
health status
physical activity
Not applicable.
==== Body
pmcIntroduction

Chronic obstructive pulmonary disease (COPD) is a progressive respiratory disorder.1,2 COPD is the fourth leading cause of death3 in Canada and is the third worldwide.4 The Public Health Agency of Canada5 reported about 4% of Canadians (approximately 780,000) aged 35 years and older were diagnosed with COPD in 2009 to 2010. In Canada, there is a substantial economic and humanistic burden from COPD.3 Individuals living with COPD experience many pulmonary and extra-pulmonary symptoms, affecting their overall quality of life and limiting their daily activities.3,6

There is increased attention on the impact of climate change on weather exposures and the effects on chronic lung diseases7 and their global health burden.8 Global climate change has increased the mean yearly ambient temperature, frequency and intensity of variable weather conditions.9 Increasing concentrations of atmospheric greenhouse gases have increased climatic temperatures, causing events of severe and prolonged heat waves, increased air pollution, and temperature variabilities.10 In Canada, the frequency and intensity of extreme weather events are predicted to increase as a result of climate variability.11

Poor air quality and extreme temperatures (both hot and cold) have been found to directly damage the lungs by inducing inflammatory responses, which may increase susceptibility to infections and risk of exacerbations.12 As a result, temperature and humidity extremes affect the lung function of individuals with COPD13 Sama et al.14 completed a cross-sectional survey examining environmental influences in individuals with COPD in Massachusetts, USA. They found that 78% of study participants were affected by hot/humid and cold/dry weather, 81% “finding it harder to breathe” in hot/humid weather, and 67% in cold/dry weather. Weather was only one of several different exposure variables they investigated; however, their impact on health outcomes was not assessed. Extremes of temperature and humidity have been associated with increases in adverse respiratory symptoms,9,15,16 reduced lung function,9,16–18 decreased health status,15,17 increased use of rescue inhalers9,16,19,20 decreased physical activity (PA),15,21,22 and increased exacerbations15,17,19,20 and hospitalizations.15,23–25 Of these studies, one conducted across Canada focused only on the effects of daily variation of weather on PA,21 and another in Northwestern, USA collected information on respiratory symptoms, exacerbations, and rescue inhaler use in cold temperatures only.9 There is a lack of evidence describing both the burden of extreme weather conditions on individuals with COPD and the impact on important health outcomes.17,25 There is also a lack of research conducted in Canada, limiting the generalizability of past results to individuals with COPD living in Canada.

The primary objective of this study was to determine what proportion of individuals with COPD were affected by extremes of weather (hot/humid and cold/dry) regarding their health status and respiratory symptoms. The secondary objective of this study was to determine the associations between extremes of weather and health status, respiratory symptoms, PA, frequency of exacerbations, rescue inhaler use, and healthcare utilization in individuals with COPD.

Materials and Methods

Study Design

A cross-sectional self-reported survey was developed to collect information on the effects of temperature and humidity on the health status, respiratory symptoms, PA, frequency of exacerbations, rescue inhaler use, and healthcare utilization in individuals with COPD in three weather conditions: moderate or “ideal” conditions (14 to 21°C and 30 to 50% relative humidity [RH]), cold/dry conditions (≤ 5°C and < 30% RH), hot/humid conditions [(≥ 25°C and > 50% RH) see Supplementary Information]. Two individuals with COPD piloted the survey and did not suggest changes to the content.

Survey Contents: Reported Health Outcomes

We have developed our survey based on previous research that has measured COPD symptoms. The COPD Assessment Test (CAT)26 assessed both symptoms and health status. Total scores ranged from 0-40, with higher scores representing worse health status. The minimum clinically important difference (MCID) of the CAT is 2 points.27 The Daily-PROactive and Clinical visit-PROactive Physical Activity (D-PPAC)28 assessed PA. Each question uses a 0 to 4-point scale; total scores normally range from 0 to 37, with a lower score indicating poorer PA (lower amount and/or higher difficulty). Because we did not measure step count and vector magnitude units, scores in this study ranged from 0 to 28. Sub-scores, D-PPAC total amount and D-PPAC difficulty were also calculated. The CAT and the D-PPAC are both valid and reliable tools that demonstrate strong internal consistency and test-retest reliability, showing the ability to measure the construct they intend to measure.26,28

Frequency of exacerbations, rescue inhaler use, healthcare utilization (doctor visits, emergency department, hospitalizations), and response actions to the weather conditions were collected. The end of the survey included items to describe our study population and identify potential confounders to weather exposure.29,30 This included demographics, daily activity and symptoms (modified Medical Research Council dyspnea scale (mMRC),31 attendance in PR and self-management program, International Physical Activity Questionnaire Short Form (IPAQ),32 respiratory medications), exacerbation history, comorbidities, prognostic indicators (e.g., smoking status, home oxygen use), and environmental variables (type of community, city size, rainfall).

Participants were asked to recall answers from the prior year (including all four seasons), not including restrictions due to the COVID-19 pandemic. The survey was completed anonymously online (SurveyMonkey® platform, San Mateo, California),33,34 by telephone or mail. Individuals received a $20 gift card for completing the survey. Ethics approval was obtained from the University (REB #: 16029).

Participants

Participants were eligible to answer the survey if they were:

40 years and older,35

Diagnosed with COPD as per GOLD criteria [2, 21] (FEV1/FVC ratio < 0.7) by a physician of any severity (mild, moderate, severe, very severe),

Resided in Canada for at least one year (not including times related to COVID-19),

Capable of providing informed consent.

Due to a poor response rate, we did not exclude individuals if they reported diagnoses of other chronic respiratory diseases or disorders, including asthma, sleep apnea, interstitial lung disease, or lung cancer. We recruited individuals from 267 pulmonary rehabilitation (PR) programs across Canada, advocacy groups, and professional respiratory organizations. We provided study posters to them and waited for individuals to contact us. Additionally, we employed snowball sampling techniques and social media (e.g., Twitter/X36) to identify potential participants.

Data Analysis

For our primary objective, individuals affected by extreme weather conditions (hot/humid or cold/dry) were defined as “responders” using the CAT score MCID36; negative responders had CAT scores ≥ 2 points compared to the ideal/moderate CAT score. Data analysis consisted of descriptive statistics, including means and standard deviations (SD) for continuous variables, median and interquartile range (IQR) for skewed data and counts and percentages for nominal variables. For open-ended questions, text feedback was grouped into overarching themes based on the corresponding weather conditions.

For the secondary objective, repeated-measures ANOVA for interval data (CAT, D-PPAC) and Cochran’s Q test for categorical dependent variables (frequency of exacerbations, rescue inhaler use, healthcare utilization) for each weather condition were performed. Due to the limited sample size, we could not adequately adjust for potential confounders. For significant results for parametric data, Bonferroni corrected pairwise post-hoc analyses were performed. IBM® SPSS Statistics was used, with a p-value < 0.05 considered significant.

Results

Initially, our survey link was publicly shared and received over 400 responses; it raised suspicions of the potential responses from spambots and/or non-eligible individuals seeking the $20 gift card.37 The survey was closed, and each response was reviewed closely. Responses that included characteristics of chronic lung disease (e.g., age, smoking duration, diagnoses, and comorbidities), and/or included sensible open-text comments were included (only n=12). We changed specific questions to filter out bot responses and did not publicly share the survey link before re-releasing the survey. Subsequently, this yielded 25 additional responses to our final dataset of n=37 (online n=31, phone n=5, mail n=1). One participant did not complete the survey in its entirety and was excluded.

Participant Characteristics

Out of 36 participants, n=29 (81%) participants reported COPD as their primary diagnosis, with the remainder reporting asthma (11 [31%]), sleep apnea (4 [11%]), interstitial lung disease (2 [6%]), or lung cancer (1 [3%]) as their primary diagnosis. Mean (SD) age was 64.5 (11), and 23 (64%) were female with mean Body Mass Index (BMI) 27.8 (8.4%). Twenty-five (69%) were formerly smoking, and 6 (17%) were currently smoking, with a mean (SD) pack per year of 39.5 (25.6). Participants lived primarily in an urban community [14 (39%)]. Many reported a precipitation level some days of the month (27 [75%]). Mean (SD) of chronic lung disease duration was 12.4 (11.2) years. With respect to PA and dyspnea, 75% (n=27) were minimally active (based on the IPAQ), with a mean (SD) Metabolic equivalent of task (MET) minutes per week of 3688.8 (3306.6) ml/kg/min. Most participants identified themselves as mMRC Grade 1 (13 [36%]) or Grade 2 dyspnea level (12 [33%]).

Tables 1 and 2 provide additional details of daily activity and symptoms, exacerbation-related variables, comorbidities, prognostic indicators, and environmental factors.

188129 Table 1. Participant Characteristics.

Characteristics	Value	
Age (years)
Mean (SD)	64.53 (11.07)	
Sex, n (%)
Female
Male	23 (63.9)
11 (30.6)	
Primary Respiratory Diagnosis*, n (%)
COPD
Asthma
Sleep Apnea
ILD
Lung Cancer	29 (80.6)
11 (30.6)
4 (11.2)
2 (5.6)
1 (2.8)	
Respiratory Disease Duration
Mean (SD)
Median (IQR)	12.40 (11.18)
9.75 (17.00)	
Comorbidities, n (%)
Bone Disorder
Cardiovascular Diseases
Type 1 or Type 2 Diabetes
Neuropsychiatric Disorders**
Cancer†
Congestive Heart Failure
Hypercholesteremia
PAD
Cirrhosis
Complex Migraines
Coronary Heart Disease
DVT
GERD
Musculoskeletal Disorders
Pulmonary Embolism	10 (27.8)
7 (19.4)
5 (13.9)
4 (11.1)
3 (8.3)
3 (8.3)
2 (5.6)
2 (5.6)
1 (2.8)
1 (2.8)
1 (2.8)
1 (2.8)
1 (2.8)
1 (2.8)
1 (2.8)	
BMI (kg/m2)
Mean (SD)
Smoking History, n (%)
Formerly Smoking
Currently Smoking
Never Smoked
PPY
Mean (SD)	27.77 (8.35)
25 (69.4)
6 (16.7)
4 (11.1)
39.5 (25.6)	
Living Arrangement, n (%)
Lives with spouse/partner
Lives alone
Lives with children
Lives with roommates
Lives with parents/guardians	15 (41.7)
11 (30.6)
5 (13.9)
2 (5.6)
1 (2.8)	
Marital Status, n (%)
Married/Common Law
Divorced/Separated
Single/Never Married
Widowed	19 (52.8)
7 (19.4)
5 (13.9)
3 (8.3)	
Level of School, n (%)
College or vocational school
Any university training
Highschool or less
Any postgraduate training	15 (41.7)
11 (30.6)
7 (19.4)
1 (2.8)	
Employment Status, n (%)
Retired
Disability
Full-Time
Self-Employed
Not employed	18 (50.0)
7 (19.4)
4 (11.1)
4 (11.1)
1 (2.8)	
Household Income, n (%)
< $25,000
25,001−45,000
45,001-$65,000
> $65,000	7 (19.4)
8 (22.2)
8 (22.2)
9 (25.0)	
Community, n (%)
Urban
Suburban
Rural	14 (38.9)
11 (30.6)
9 (25.0)	
Community Population Size, n (%)
Large (≥ 100,000)
Medium (30,000-99,999)
Small (1,000-29,999)	16 (44.4)
8 (22.2)
10 (27.8)	
Precipitation Level, n (%)
Most days of the month
Some days of the month
Few days of the month
Very few days of the month	1 (2.8)
27 (75.0)
4 (11.1)
2 (5.6)	
Respiratory Medications, n (%)
SABA
Combination Inhalers‡
LABA
Oral Corticosteroid Pills
Antibiotics
Other: Nebulizer, Mucolytics, P-4 Inhibitors	30 (83.3)
27 (75.0)
12 (33.3)
7 (19.4)
6 (16.7)
6 (16.7)	
Vaccines, n (%)
Influenza
Pneumococcal	27 (75.0)
18 (50.0)	
O2 Therapy, n ( (%)	14 (38.9)	
CPAP or NIV, n ( (%)	6 (16.7)	
Acute exacerbation in last year, n ( (%)	19 (52.8)	
ER visits in last year, n ( (%)	10 (27.8)	
Bone Fracture in last year, n ( (%)	3 (8.3)	
Swelling (ankles, legs, feet), n ( (%)	13 (36.1)	
PR Attendance, n ( (%)	22 (61.1)	
Self-Management Education Program, n ( (%)	13 (36.1)	
Total sample size n=36 (n=2 did not complete demographics but were included in the denominator). *Some individuals identified more than one primary respiratory diagnosis. **Neuropsychiatric disorders: Anxiety, Depression †Cancers: Lung and Breast ‡Combination Inhalers: salbutamol, fluticasone, vilanterol, budesonide, aclidinium bromide. BMI: Body Mass Index; CPAP: Continuous positive airway pressure therapy; COPD: chronic obstructive pulmonary disease; DVT: Deep Vein Thrombosis; ER: Emergency Room; GERD: Gastroesophageal Reflux Disease; ILD: Interstitial Lung Disease; IQR: interquartile range; LABA: Long-acting beta-agonists; NIV: Non-invasive ventilation; P-4 Inhibitors: Phosphodiesterase-4 Inhibitor; PAD: Peripheral Artery Disease; PPY: Packs smoked per year; PR: Pulmonary Rehabilitation; O2: Oxygen; SABA: Short-acting beta-agonists; SD: standard deviation.

188130 Table 2. Physical Activity and Dyspnea Baseline Measurements.

Measurements	Value	
IPAQ level of physical activity, n (%)
Inactive
Minimally Active
HEPA Active	
2 (5.6)
27 (75.0)
5 (13.9)	
Total METs minutes, n=36
Mean (SD)
Median (IQR [25%-75%])	
3688.8 (3306.6)
2099.5 (1264.6-6824.3)	
mMRC Scale, n (%)
Grade 0
Grade 1
Grade 2
Grade 3
Grade 4	
2 (5.6)
13 (36.1)
12 (33.3)
7 (19.4)
1 (2.8)	
Total sample size n=36 (n=2 did not complete demographics but were included in the denominator). HEPA: health-enhancing physical activity; a high active category; IPAQ: International Physical Activity Questionnaire; IQR: interquartile range; MET: Metabolic equivalent of task; mMRC: modified Medical Research Council; SD: standard deviation.

Influence of Extreme Weather Conditions

Most responders to the two weather extremes were negative or worse compared to ideal: 23 (66%) in cold/dry and 24 (69%) in hot/humid. Only 9 (25%) were positive responders, and 14 (40%) were non-responders (Table 3).

188131 Table 3. Proportion of CAT Score Responders in Extreme Weather Conditions.

Weather	Responder Type	n (%)	
Cold & Dry vs Ideal	Negative Responder
Not Responder
Positive Responder	23 (65.7)
8 (22.9)
4 (11.4)	
Hot & Humid vs Ideal	Negative Responder
Not Responder
Positive Responder	24 (68.6)
6 (17.1)
5 (14.3)	
Total sample size n=36 (missing n=1). CAT: COPD Assessment Test.CAT negative/positive responder= score increased/decreased by 2

Mean (SD) CAT score was significantly different between the three weather conditions (p < 0.001), Table 4. Health status in ideal weather conditions (17.2 [7.8]) was significantly higher compared to hot/humid (22.4 [7.4] p< 0.001) and cold/dry conditions (21.4 [8.3], p< 0.001). Both extremes of weather resulted in clinically important decreases in health status (MCID > 4 points).

188132 Table 4. Weather Conditions and Outcomes.

Variable	Ideal Conditions	Hot/humid Conditions	Cold/dry Conditions	p-value	
CATa
Mean (SD)	n=36
17.2 (7.8)	n=35
22.4 (7.4)	n=36
21.4 (8.3)	p< 0.001	
D-PPAC totalb
Mean (SD)	n=36
13.0 (3.1)	n=36
14.7 (3.9)	n=36
12.2 (4.5)	p< 0.001	
D-PPAC amount c
Mean (SD)	n=36
4.4 (1.4)	n=36
2.3 (2.0)	n=36
2.2 (1.4)	p< 0.001	
D-PPAC difficultyd
Mean (SD)	n=36
8.6 (3.6)	n=36
12.4 (4.0)	n=36
10.1 (4.6)	p< 0.001	
Exacerbationse, n (%)
No
Yes	
15 (41.7)
21 (58.3)	
5 (12.9)
30 (83.3)	
7 (19.4)
29 (80.6)	p=0.002	
Rescue inhaler use, n (%)
No
Yes	
12 (33.3)
24 (66.7)	
7 (19.4)
28 (77.8)	
7 (19.4)
29 (80.6)	p=0.05	
Family doctor visit, n (%)
No
Yes	
32 (88.9)
3 (8.3)	
27 (75.0)
8 (22.2)	
27 (75.0)
9 (25.0)	p=0.148	
Respirologist specialist, n (%)
No
Yes	
31 (86.1)
5 (13.9)	
28 (77.8)
7 (19.4)	
30 (83.3)
6 (16.7)	p=0.761	
ED visit, n (%)
No
Yes	
34 (94.4)
2 (5.6)	
30 (83.3)
5 (13.9)	
30 (83.3)
6 (16.7)	p=0.307	
Hospitalization, n (%)
No
Yes	
35 (97.2)
1 (2.8)	
31 (86.1)
4 (11.1)	
29 (80.6)
7 (19.4)	p=0.034	
Total sample size n=36. Mild exacerbation = no change in prescribed medications, Moderate exacerbation = required prescribed antibiotic and/or oral corticosteroid, Severe exacerbation = required a hospital admission or emergency department visit. Higher CAT scores represent poorer health status. Lower D-PPAC scores represent reduced physical activity. aideal vs hot/humid, p=0.0005; ideal vs cold/dry, p=0.0001. bideal vs hot/humid, p=0.008; hot/humid vs cold/dry, p=0.00002. cideal vs hot/humid, p< 0.001; ideal vs cold/dry, p< 0.001. dideal vs hot/humid, p< 0.001; ideal vs cold/dry, p< 0.001. eideal vs hot/humid, p=0.002. CAT: COPD Assessment Test; D-PPAC: Daily-PROactive Physical Activity in COPD; ED: Emergency Department; SD: standard deviation.

Mean (SD) D-PPAC total score significantly differed between each weather condition (p< 0.001), Table 4. Post hoc tests revealed a significant increase in overall PA in the hot/humid conditions, 14.7 (3.9) compared to ideal conditions, 13.0 (3.1), p=0.008. There was a decrease in PA in cold/dry conditions 12.2 (4.5) compared to ideal conditions, but it was not statistically significant (p=0.364).

Mean (SD) D-PPAC amount score was significantly worse in both cold/dry (2.2 [1.4]) and hot/humid (2.3 [2.0]), compared to ideal conditions (4.4 [1.4]), p < 0.001. D-PPAC difficulty score was significantly better in both cold/dry at 10.1 (4.6), and hot/humid at 12.4 (4.0) compared to ideal conditions, 8.6 (3.6), p< 0.001.

Exacerbations and health utilization were higher in extremes of weather, with the frequency of exacerbations (p=0.002), rescue inhaler use (p=0.05) and hospitalizations (p=0.034) significantly different between each of the three weather conditions, as shown in Figure 1 and Table 4. The only significant pairwise post-hoc result was the number of exacerbations between ideal/moderate and hot/humid conditions, p=0.002. In ideal/moderate conditions, n=15 (42%) did not have an exacerbation, and n=21 (58%) did have an exacerbation. In hot/humid conditions, n=30 (83%) had an exacerbation.

188133 Figure 1. Type and Frequency of Healthcare Utilization Between Weather Conditions.

p-values <0.05 = significant. GP: General Practitioner; ED: Emergency Department.

Most participants reported taking no action during ideal conditions, 21 (58%). In cold/dry conditions, 15 (42%) reported avoiding going outside or stayed indoors, 9 (25%) and 7 (19%) limited time outside or used medications. During hot/humid conditions, 27 (75%) avoided going outside or stayed indoors.

Participants’ perceptions and mitigation strategies in different weather conditions

At the end of the survey, some participants (n=12) elaborated on how specific weather conditions affected them. Extreme weather conditions, whether hot or cold, were troublesome for their health, with four participants reporting more problematic effects from hot/humid weather conditions than cold/dry weather. These conditions were perceived as “very big factors in my overall health.” Higher temperatures and humidities were found to make it difficult for participants to “breathe and function.” One participant described extreme heat and humidity as causing a”very definite decrease in quality of life.” Another participant described cold weather conditions as “tearing their lungs.” One participant found cold and humid conditions problematic, as “extreme cold and humidity play a very big factor in their overall health.”

Common strategies participants used to prevent the consequences of different weather conditions were avoidance, inhalers, oxygen therapy, and humidification. In ideal temperatures or humid (cold or hot) conditions, participants reported minimal interventions were needed. However, some individuals spent limited time outside despite ideal weather conditions and still needed inhalers and oxygen therapy. In both extreme conditions, participants expressed limited time outside or avoidance. For hot and humid days, many participants conveyed using air conditioning or fans to stay cool. However, some participants noted problems in breathing when air conditioning was set too high (cold). In cold and dry conditions, participants expressed they would also dress warmer. Additionally, participants noted they would use their rescue inhalers before leaving the house for both weather extremes.

Discussion

This study examined the effects of extremes of temperature and humidity on health outcomes in individuals with COPD living in Canada, the majority expressing clinically important decreases in their health status and increased healthcare utilization in both extreme weather conditions. Exacerbation frequency was higher in hot/humid weather. PA score was lower in cold/dry conditions but increased in hot/humid conditions; the amount and difficulty level of PA was reduced in both extreme conditions. There were no significant differences in rescue inhaler use, family doctor and respiratory specialist visits, hospitalizations, or emergency department visits across the three weather conditions.

Cold/Dry vs. Ideal Weather Conditions

In cold/dry weather conditions, we found that participants experienced a lower health status in comparison to ideal conditions. Our findings correlate with those of Miravitlles et al.39, who found worsened health status in the winter compared to the spring and summer seasons. There may be a threshold below which colder temperatures adversely impact respiratory health19,38 as Scheerens et al.39 found in participants with COPD, each 5°C increase in temperature was associated with worsening breathing symptoms and each 5°C decrease in outdoor temperature was associated with worsening cough.

In terms of PA, our study found associations between cold/dry conditions and lower PA, both in the amount and difficulty level. We did not collect data on the types of activities, but we believe during cold/dry conditions, participants decreased their PA and engaged in less vigorous activities. These results align with past studies that reported associations between colder weather and lower PA levels.40,41 Thorpe et al.42 found that some patients would not leave their homes because cold weather made them experience more respiratory symptoms, such as excess coughing, sneezing, and shortness of breath. This is similar to the open-text feedback we received in our survey. With respect to difficulty levels, the literature does support our association of decreased level of activity in colder conditions. Hoaas et al.41 conducted a study in Norway, Denmark and Australia and showed individuals living with COPD walked less and decreased their PA in cooler seasons compared to summer.

The decrease in health status and PA in cold/dry weather may be due to a number of reasons. First, several studies have identified 18°C as a potential threshold of indoor temperature below which adverse health effects may occur.19,38,43,44 These adverse health effects include increased blood pressure and risks of blood clots,43 and increased susceptibility to lung infections and vulnerability to the common cold.23 With respect to PA, colder temperatures may lead to increased bronchoconstriction,45 which has been associated with decreased PA.46

Hot/Humid vs. Ideal Weather Conditions

In hot/humid conditions, there was an association with lower health status and adverse respiratory symptoms. Patients in previous studies reported the summer heat to be an uncontrollable trigger, causing increased morning dyspnea, reduced peak expiratory flow rates and poorer health status.15,47

Participants in our study also reported increased exacerbations during hot/humid conditions. Higher temperatures have been associated with an increase in exacerbations,20 hospitalizations due to exacerbations (5.4% for every 1°C increase),23 and a risk of death due to COPD up to 25%.48,49 Additionally, for individuals with chronic disease, heat waves have been associated with increased morbidity and frequency of hospitalizations.50 In terms of humidity, high relative humidity is associated with worsening of COPD symptoms and increased hospitalizations due to acute exacerbations.51 Jevti et al.52 found for each 10% increase in relative humidity, hospitalizations due to acute exacerbations increased by 0.8%.52

The pathophysiological mechanisms of the association between heat exposure and exacerbation of COPD symptoms leading to hospitalizations are not well understood.24 The heat exposure may induce cytokine release, triggering inflammatory responses causing hyperventilation.53,54 Hyperventilation may lead to acute bronchoconstriction in individuals with pre-existing COPD, exacerbating their dyspnea.55–57 Lin et al.18 speculated that higher temperatures could induce bronchoconstriction58 and elevate concentrations of biological aerosols, which can cause inflammatory and allergic responses in the respiratory tract.59

Our study found hot/humid conditions were associated with higher overall PA, compared to ideal conditions. Although the amount of PA was significantly lower, the overall D-PPAC score was higher due to the decrease in the level of activity difficulty. Prior research conflicts with our results, mainly reporting increases in the amount and difficulty of PA in hot and/or humid weather conditions. Previous studies have found an increase in temperature was associated with a higher amount of PA.21,22 Hoaas et al.41 found individuals with COPD had increased difficulty levels of PA in warmer weather conditions. Although our PA results during higher temperatures contrasted with prior research, they were similar when considering the humidity level. Studies found higher humidities were associated with a decrease in PA.22,60,61 We could not find studies supporting our results of decreased PA difficulty in hot and humid conditions. It is recommended that both the amount and magnitude of PA be measured when investigating the impact of different extremes of weather conditions on individuals with COPD.62

Strengths and Limitations

Strengths

Our study is one of the few that collected information of the effects of temperature and humidity on health outcomes in individuals with COPD living in Canada. Our study used measures (CAT and D-PPAC) that were reliable and valid26,28,31,32,63–65 and defined positive and negative responders27,36,63 to weather extremes. We utilized good recruitment strategies, despite the challenges associated with the COVID-19 pandemic. Our sample had representation from various parts of Canada from different communities of large, medium, and small population sizes. We conducted the survey using multi-modal methods (online/phone/mail) to optimize timeliness and accessibility.66 We collected contextual feedback from participants that would not have been revealed through the close-ended questions, such as other problematic weather conditions and strategies to mitigate negative consequences of weather conditions.

Limitations

Several limitations include the sample size and the generalizability of these results. Our study may have suffered from recall bias and/or under- or over-estimations.67 We included individuals with any illness severity level and diagnoses of other chronic respiratory conditions, possibly influencing the results. However, the overlap of these respiratory disorders is common for individuals with COPD.68,69 The overall survey was not validated; however, as mentioned above, it contained validated instruments. Additionally, the number of questions on the survey may have caused answer fatigue and resulted in more neutral answers. Finally, our survey was anonymous and was affected by bots; results from the first dataset (n=12) and second dataset (n=25) may have differed because we changed specific questions to filter out bot responses before re-releasing the survey. Nevertheless, we were conservative when deciding on legitimate responses, and each item was reviewed closely.

Our study was open to individuals across Canada, and the weather in individual provinces differs. For example, British Columbia experiences cold and humid weather based on participant text feedback, and in our study, we only assessed cold and dry weather conditions. In addition, we likely did not have any French-speaking participants because we did not have the resources to translate the survey. Our sample may not be generalizable to the entire COPD population in Canada due to these limitations; however, this study serves as a pilot study to provide important implications for future research studies.

Future Research

To better understand the impact of weather on individuals with COPD, minimizing the influence of other confounding factors is required. This includes using prospective designs, incorporating individuals with homogenous respiratory disease, and targeting regional weather conditions rather than generalizing for all of Canada. We recommend using objective measurements to identify responders to extreme weather conditions, such as the CAT and D-PPAC, and measuring both PA quantity and magnitude. Studies should consider all spectrums and combinations of temperature and humidity, such as hot and cold temperatures with high and low humidity. The experiences of individuals with COPD in different weather conditions using a qualitative approach should be considered, especially given the varied open-text responses in this study. Other meteorological factors, such as barometric pressure, solar radiation, wind, and even air quality, could also be considered. Finally, future research should involve the development and evaluation of management and coping strategies to help alleviate adverse symptoms and the limitations of individuals with COPD in extreme weather conditions.

Conclusion

This study showed that individuals with COPD living in Canada may be negatively affected by both extremes of hot/humid and cold/dry conditions. This negative response was associated with decreased health status, decreased PA (amount and difficulty level), and increases in exacerbations, rescue inhaler use, and hospitalizations. The development of preventative and management programs is necessary to help individuals with COPD cope with different weather conditions as climate change is a driving factor of increased extreme weather conditions.

Contributors

MN, SM, BB, PA (latter two, patient collaborators) conceptualized the study and designed the survey. MN, SM, CB, WS were involved in the data acquisition, data analysis, and interpretation. MN, SM, SQ, CB, WS drafted, reviewed and finalized the manuscript.

Competing Interests

No potential competing interest was reported by the authors.

Ethical Declarations

Ethics approval was obtained from the University (REB #: 16029).

Supplementary Material

Supplementary Information

Acknowledgments

Thank you to Mr. Ben Bowles and Ms. Pauline Anderson, who have graciously provided feedback and helped develop the proposal and survey. Thank you to the program coordinators who shared the survey, as we were unable to actively recruit participants due to COVID-19.
==== Refs
The GOLD Summit on chronic obstructive pulmonary disease in low- and middle-income countries The International Journal of Tuberculosis and Lung Disease Halpin D. M. G. Celli B. R. Criner G. J. Frith P. López Varela M. V. Salvi S. Vogelmeier C. F. Chen R. Mortimer K. Montes de Oca M. Aisanov Z. Obaseki D. Decker R. Agusti A. 1 11 2019
23 11 1131 1141 1027-3719 10.5588/ijtld.19.0397 10.5588/ijtld.19.0397
GOLD report: 2022 update The Lancet Respiratory Medicine Venkatesan Priya 2 2022
10 2 e20 2213-2600 10.1016/s2213-2600(21)00561-0 10.1016/s2213-2600(21)00561-0 34942084
Clinical, humanistic, and economic burden of chronic obstructive pulmonary disease (COPD) in Canada: a systematic review BMC Research Notes Dang-Tan Tam Ismaila Afisi Zhang Shiyuan Zarotsky Victoria Bernauer Mark 21 9 2015
8 1 464 1756-0500 10.1186/s13104-015-1427-y 10.1186/s13104-015-1427-y 26391471
Chronic obstructive pulmonary disease (COPD) [Internet]. World Health Organization World Health Organization 2023
https://www.who.int/news-room/fact-sheets/detail/chronic-obstructive-pulmonary-disease-(copd) cited 2023Apr3]. Available from:
Government of Canada Public Health Agency of Canada 2023-3-30 https://www.canada.ca/en/public-health/services/chronic-diseases/reports-publications/fast-facts-about-chronic-obstructive-pulmonary-disease-copd-2011.html Government of Canada [Internet]. Government of Canada; 2019 [cited 2023Mar30]. Available from:
Breaking the Surface - Breaking the Silence: How the under-reporting of "Lung Attacks" in Canada impacts patient outcomes in COPD Chapman K R Kaplan A 2012
2023-3-30 http://copdcanada.info/resources/Breaking+the+Surface+-+Breaking+the+Silence+2012.pdf cited 2023Mar30]. Available from:
Lungs in a warming world: climate change and respiratory health Chest Bernstein Aaron S. Rice Mary B. 5 2013
143 5 1455 1459 0012-3692 10.1378/chest.12-2384 10.1378/chest.12-2384 23648909
Interactive effects of high temperature and ozone on COPD deaths in Shanghai Atmospheric Environment Fu Shihua Zhou Yi Peng Li Ye Xiaofang Yang Dandan Yang Sixu Zhou Ji Luo Bin 6 2022
278 119092 119092 1352-2310 10.1016/j.atmosenv.2022.119092 10.1016/j.atmosenv.2022.119092
Colder temperature is associated with increased COPD morbidity European Respiratory Journal McCormack Meredith C. Paulin Laura M. Gummerson Christine E. Peng Roger D. Diette Gregory B. Hansel Nadia N. 6 2017
49 6 1601501 0903-1936 10.1183/13993003.01501-2016 10.1183/13993003.01501-2016 28663313
Climate Change and Air Pollution: Effects on Respiratory Allergy Allergy, Asthma & Immunology Research D'Amato Gennaro Pawankar Ruby Vitale Carolina Lanza Maurizia Molino Antonio Stanziola Anna Sanduzzi Alessandro Vatrella Alessandro D'Amato Maria 2016
8 5 391 2092-7355 10.4168/aair.2016.8.5.391 10.4168/aair.2016.8.5.391 27334776
Science narrative climate change impacts on the health of Canadians [Internet Government of Canada Publications Public Health Agency of Canada 2017
2023-3-31 https://publications.gc.ca/collections/collection_2017/aspc-phac/HP5-122-2017-eng.pdf cited 2023Mar31]. Available from:
Understanding the relationships between environmental factors and exacerbations of COPD Expert Review of Respiratory Medicine Gayle Alicia V Quint Jennifer K Fuertes Elaine I 2021
15 1 39 50 1747-6348 10.1080/17476348.2020.1801426 10.1080/17476348.2020.1801426 32713218
The Effects of Air Pollution and Temperature on COPD COPD: Journal of Chronic Obstructive Pulmonary Disease Hansel Nadia N. McCormack Meredith C. Kim Victor 18 12 2015
13 3 372 379 1541-2555 10.3109/15412555.2015.1089846 10.3109/15412555.2015.1089846 26683097
Environmental triggers of COPD symptoms: a cross sectional survey COPD Research and Practice Sama Susan R. Kriebel David Gore Rebecca J. DeVries Rebecca Rosiello Richard 12 2015
1 1 2054-9040 10.1186/s40749-015-0016-8 10.1186/s40749-015-0016-8
Towards an assessment of perceived COPD exacerbation triggers: Initial development and validation of a questionnaire Respirology Werchan Chelsey A. Steele Ashton M. Janssens Thomas Millard Mark W. Ritz Thomas 13 7 2018
24 1 48 54 1323-7799 10.1111/resp.13368 10.1111/resp.13368
Respiratory Effects of Indoor Heat and the Interaction with Air Pollution in Chronic Obstructive Pulmonary Disease Annals of the American Thoracic Society McCormack Meredith C. Belli Andrew J. Waugh Darryn Matsui Elizabeth C. Peng Roger D. Williams D’Ann L. Paulin Laura Saha Anik Aloe Charles M. Diette Gregory B. Breysse Patrick N. Hansel Nadia N. 12 2016
13 12 2125 2131 2329-6933 10.1513/annalsats.201605-329oc 10.1513/annalsats.201605-329oc 27684429
Tele-monitoring reduces exacerbation of COPD in the context of climate change–a randomized controlled trial Environmental Health Jehn Melissa Donaldson Gavin Kiran Bahar Liebers Uta Mueller Klaus Scherer Dieter Endlicher Wilfried Witt Christian 21 11 2013
12 1 99 1476-069X 10.1186/1476-069x-12-99 10.1186/1476-069x-12-99 24261700
Effects of ambient temperature on lung function in patients with chronic obstructive pulmonary disease: A time-series panel study Science of The Total Environment Lin Zhijing Gu Yutong Liu Cong Song Yuanlin Bai Chunxue Chen Renjie Chen Shujing Kan Haidong 4 2018
619-620 360 365 0048-9697 10.1016/j.scitotenv.2017.11.035 10.1016/j.scitotenv.2017.11.035 29156256
Seasonality and determinants of moderate and severe COPD exacerbations in the TORCH study European Respiratory Journal Jenkins C. R. Celli B. Anderson J. A. Ferguson G. T. Jones P. W. Vestbo J. Yates J. C. Calverley P. M. A. 7 7 2011
39 1 38 45 0903-1936 10.1183/09031936.00194610 10.1183/09031936.00194610 21737561
The effect of cold temperature on increased exacerbation of chronic obstructive pulmonary disease: a nationwide study PLoS One Tseng Ching-Min Chen Yung-Tai Ou Shuo-Ming Hsiao Yi-Han Li Szu-Yuan Wang Shuu-Jiun Yang Albert C. Chen Tzeng-Ji Perng Diahn-Warng 15 3 2013
8 3 e57066 1932-6203 10.1371/journal.pone.0057066 10.1371/journal.pone.0057066 23554858
The Relationship Between Weather and Objectively Measured Physical Activity Among Individuals With COPD J Cardiopulm Rehabil Prev Balish Shea M. Dechman Gail Hernandez Paul Spence John C. Rhodes Ryan E. McGannon Kerry Blanchard Chris 11 2017
37 6 445 449 1932-7501 10.1097/hcr.0000000000000244 10.1097/hcr.0000000000000244
Physical Activity of Patients with COPD from Regions with Different Climatic Variations COPD: Journal of Chronic Obstructive Pulmonary Disease Furlanetto Karina Couto Demeyer Heleen Sant'anna Thais Hernandes Nidia Aparecida Camillo Carlos Augusto Pons Ignasi Serra Gosselink Rik Troosters Thierry Pitta Fabio 7 4 2017
14 3 276 283 1541-2555 10.1080/15412555.2017.1303039 10.1080/15412555.2017.1303039 28388284
Excess mortality and morbidity during the July 2006 heat wave in Porto, Portugal International Journal of Biometeorology Monteiro Ana Carvalho Vânia Oliveira Teresa Sousa Carlos 2013
57 1 155 167 0020-7128 10.1007/s00484-012-0543-9 10.1007/s00484-012-0543-9
Ambient heat and hospitalisation for COPD in Brazil: a nationwide case-crossover study Thorax Zhao Qi Li Shanshan Coelho Micheline de Sousa Zanotti Staglior Saldiva Paulo Hilário Nascimento Xu Rongbin Huxley Rachel R Abramson Michael J Guo Yuming 13 9 2019
74 11 1031 1036 0040-6376 10.1136/thoraxjnl-2019-213486 10.1136/thoraxjnl-2019-213486
Influence of air pressure, humidity, solar radiation, temperature, and wind speed on ambulatory visits due to chronic obstructive pulmonary disease in Bavaria, Germany International Journal of Biometeorology Ferrari Uta Exner Teresa Wanka Eva R Bergemann Christoph Meyer-Arnek Julian Hildenbrand Beate Tufman Amanda Heumann Christian Huber Rudolf M Bittner Michael Fischer Rainald 2012
56 1 137 143 0020-7128 10.1007/s00484-011-0405-x 10.1007/s00484-011-0405-x 21301889
Development and first validation of the COPD Assessment Test European Respiratory Journal Jones P. W. Harding G. Berry P. Wiklund I. Chen W-H. Kline Leidy N. 31 8 2009
34 3 648 654 0903-1936 10.1183/09031936.00102509 10.1183/09031936.00102509
Assessing health-related quality of life in COPD: comparing generic and disease-specific instruments with focus on comorbidities BMC Pulmonary Medicine Wacker Margarethe E. Jörres Rudolf A. Karch Annika Wilke Sarah Heinrich Joachim Karrasch Stefan Koch Armin Schulz Holger Watz Henrik Leidl Reiner Vogelmeier Claus Holle Rolf 10 5 2016
16 1 1471-2466 10.1186/s12890-016-0238-9 10.1186/s12890-016-0238-9 27160582
The PROactive instruments to measure physical activity in patients with chronic obstructive pulmonary disease European Respiratory Journal Gimeno-Santos Elena Raste Yogini Demeyer Heleen Louvaris Zafeiris de Jong Corina Rabinovich Roberto A. Hopkinson Nicholas S. Polkey Michael I. Vogiatzis Ioannis Tabberer Maggie Dobbels Fabienne Ivanoff Nathalie de Boer Willem I. van der Molen Thys Kulich Karoly Serra Ignasi Basagaña Xavier Troosters Thierry Puhan Milo A. Karlsson Niklas Garcia-Aymerich Judith 28 5 2015
46 4 988 1000 0903-1936 10.1183/09031936.00183014 10.1183/09031936.00183014 26022965
Comprehensive respiratory assessment in advanced COPD: a ‘campus to clinic’ translational framework Thorax Steiner Michael C Evans Rachael A Greening Neil J Free Robert C Woltmann Gerrit Toms Nicole Morgan Michael D 11 5 2015
70 8 805 808 0040-6376 10.1136/thoraxjnl-2015-206948 10.1136/thoraxjnl-2015-206948
Canadian Thoracic Society Clinical Practice guideline on pharmacotherapy in patients with COPD – 2019 update of evidence Canadian Journal of Respiratory, Critical Care, and Sleep Medicine Bourbeau Jean Bhutani Mohit Hernandez Paul Aaron Shawn D. Balter Meyer Beauchesne Marie-France D’Urzo Anthony Goldstein Roger Kaplan Alan Maltais François Sin Don D. Marciniuk Darcy D. 2 10 2019
3 4 210 232 2474-5332 10.1080/24745332.2019.1668652 10.1080/24745332.2019.1668652
Evaluation of clinical methods for rating dyspnea Chest Mahler Donald A. Wells Carolyn K. 3 1988
93 3 580 586 0012-3692 10.1378/chest.93.3.580 10.1378/chest.93.3.580 3342669
International physical activity questionnaire: 12-country reliability and validity Medicine & Science in Sports & Exercise Craig CORA L. Marshall ALISON L. Sjöström MICHAEL BAUMAN ADRIAN E. BOOTH MICHAEL L. AINSWORTH BARBARA E. PRATT MICHAEL EKELUND ULF YNGVE AGNETA SALLIS JAMES F. OJA PEKKA 8 2003
35 8 1381 1395 0195-9131 10.1249/01.mss.0000078924.61453.fb 10.1249/01.mss.0000078924.61453.fb 12900694
Self-management behaviors to reduce exacerbation impact in COPD patients: a Delphi study International Journal of Chronic Obstructive Pulmonary Disease Korpershoek Yvonne J Bruins Slot Joyce C Effing Tanja W Schuurmans Marieke J Trappenburg Jaap C 9 2017
Volume 12 2735 2746 1178-2005 10.2147/copd.s138867 10.2147/copd.s138867 28979116
Improving physical activity, sedentary behaviour and sleep in COPD: perspectives of people with COPD and experts via a Delphi approach PeerJ Lewthwaite Hayley Effing Tanja W. Lenferink Anke Olds Tim Williams Marie T. 27 4 2018
6 e4604 2167-8359 10.7717/peerj.4604 10.7717/peerj.4604 29719731
What causes COPD? COPD Foundation 2023-3-31 https://www.copdfoundation.org/What-is-COPD/Understanding-COPD/What-Causes-COPD.aspx Internet]. COPD Foundation. [cited 2023Mar31]. Available from:
Validity and responsiveness of the Daily- and Clinical visit-PROactive Physical Activity in COPD (D-PPAC and C-PPAC) instruments Thorax Garcia-Aymerich Judith Puhan Milo A Corriol-Rohou Solange de Jong Corina Demeyer Heleen Dobbels Fabienne Erzen Damijan Frei Anja Gimeno-Santos Elena Hopkinson Nicholas S Ivanoff Nathalie Karlsson Niklas Louvaris Zafeiris Polkey Michael I Rabinovich Roberto A Scuri Mario Tabberer Maggie Vogiatzis Ioannis Troosters Thierry 21 1 2021
76 3 228 238 0040-6376 10.1136/thoraxjnl-2020-214554 10.1136/thoraxjnl-2020-214554 33479044
How to battle the bots wrecking your online study Simone M. 2019
2023-3-31 https://behavioralscientist.org/how-to-battle-the-bots-wrecking-your-online-study/ cited 2023Mar31]. Available from:
Mortality related to cold and air pollution in London after allowance for effects of associated weather patterns Environmental Research Keatinge W.R. Donaldson G.C. 7 2001
86 3 209 216 0013-9351 10.1006/enrs.2001.4255 10.1006/enrs.2001.4255 11453671
The impact of personal and outdoor temperature exposure during cold and warm seasons on lung function and respiratory symptoms in COPD ERJ Open Research Scheerens Charlotte Nurhussien Lina Aglan Amro Synn Andrew J. Coull Brent A. Koutrakis Petros Rice Mary B. 14 3 2022
8 1 00574 2021 2312-0541 10.1183/23120541.00574-2021 10.1183/23120541.00574-2021 35295231
Influence of weather and atmospheric pollution on physical activity in patients with COPD Respiratory Research Alahmari Ayedh D. Mackay Alex J. Patel Anant R.C. Kowlessar Beverly S. Singh Richa Brill Simon E. Allinson James P. Wedzicha Jadwiga A. Donaldson Gavin C. 13 6 2015
16 1 71 1465-993X 10.1186/s12931-015-0229-z 10.1186/s12931-015-0229-z 26071400
Seasonal variations in objectively assessed physical activity among people with COPD in two Nordic countries and Australia: a cross-sectional study. International Journal of Chronic Obstructive Pulmonary Disease Hoaas Hanne Zanaboni Paolo Hjalmarsen Audhild Morseth Bente Dinesen Birthe Burge Angela T Cox Narelle S Holland Anne E 6 2019
14 1219 1228 1178-2005 10.2147/copd.s194622 10.2147/copd.s194622 31239657
Barriers to and enablers of physical activity in patients with COPD following a hospital admission: a qualitative study International Journal of Chronic Obstructive Pulmonary Disease Thorpe Olivia Kumar Saravana Johnston Kylie 21 1 2014
9 115 128 1178-2005 10.2147/copd.s54457 10.2147/copd.s54457 24489465
Minimum indoor temperature threshold recommendations for English homes in winter – A systematic review Public Health Jevons R. Carmichael C. Crossley A. Bone A. 7 2016
136 4 12 0033-3506 10.1016/j.puhe.2016.02.007 10.1016/j.puhe.2016.02.007 27106281
Housing, energy and thermal comfort: A review of 10 countries within the WHO European Region World Health Organization 2007
2023-3-31 https://apps.who.int/iris/handle/10665/107815 cited 2023Mar31]. Available from:
Bronchoconstriction due to cold weather in COPD. The roles of direct airway effects and cutaneous reflex mechanisms. Chest Koskela Heikki O. Tukiainen Hannu O. Koskela Anna K 9 1996
110 3 632 636 0012-3692 10.1378/chest.110.3.632 10.1378/chest.110.3.632 8797403
Influence of season on exacerbation characteristics in patients with COPD Chest Donaldson Gavin C. Goldring James J. Wedzicha Jadwiga A. 1 2012
141 1 94 100 0012-3692 10.1378/chest.11-0281 10.1378/chest.11-0281
The influence of spring and summer New England meteorologic conditions on the respiratory status of patients with chronic lung disease Chest Mann Marianne Patel Kaushik Reardon Jane Z. Goldstein Mel Godar Thomas J. ZuWallack Richard L. 5 1993
103 5 1369 1374 0012-3692 10.1378/chest.103.5.1369 10.1378/chest.103.5.1369 8486012
The effect of heat waves on mortality in susceptible groups: a cohort study of a mediterranean and a northern European City Environmental Health Oudin Åström Daniel Schifano Patrizia Asta Federica Lallo Adele Michelozzi Paola Rocklöv Joacim Forsberg Bertil 29 3 2015
14 1 30 1476-069X 10.1186/s12940-015-0012-0 10.1186/s12940-015-0012-0 25889290
The effect of weather on respiratory and cardiovascular deaths in 12 U.S. cities. Environmental Health Perspectives Braga Alfésio L F Zanobetti Antonella Schwartz Joel 9 2002
110 9 859 863 0091-6765 10.1289/ehp.02110859 10.1289/ehp.02110859 12204818
The Effects of Climate Change on Patients With Chronic Lung Disease. A Systematic Literature Review Dtsch Arztebl Int Witt Christian Schubert Jean André Jehn Melissa Holzgreve Alfred Liebers Uta Endlicher Wilfried Scherer Dieter 21 12 2015
112 51-52 878 883 1866-0452 10.3238/arztebl.2015.0878 10.3238/arztebl.2015.0878 26900154
Spatial patterns and effects of air pollution and meteorological factors on hospitalization for chronic lung diseases in Beijing, China Science China Life Sciences Tian Lin Yang Chuan Zhou Zijun Wu Ziting Pan Xiaochuan Clements Archie C. A. 21 1 2019
62 10 1381 1388 1674-7305 10.1007/s11427-018-9413-y 10.1007/s11427-018-9413-y
Air pollution and hospital admissions for chronic obstructive pulmonary disease in Novi Sad HealthMED Jevti M. Dragi'c N. Bijelovi'c S. Popovi'c M. 2012
6 4 1207 15 https://www.researchgate.net/publication/286355085_Air_pollution_and_hospital_admissions_for_chronic_obstructive_pulmonary_disease_in_Novi_Sad Available from:
Role of blood components in mediating lung vascular injury after pulmonary vascular thrombosis Chest Malik A.B. Johnson A. Tahamont M.V. van der Zee Hoyte Blumenstock F.A. 5 1983
83 5Suppl 21S 24S 0012-3692 10.1378/chest.83.5_supplement.21s 10.1378/chest.83.5_supplement.21s 6839843
High temperature and hospitalizations for cardiovascular and respiratory causes in 12 European cities American Journal of Respiratory and Critical Care Medicine Michelozzi Paola Accetta Gabriele De Sario Manuela D'Ippoliti Daniela Marino Claudia Baccini Michela Biggeri Annibale Anderson H. Ross Katsouyanni Klea Ballester Ferran Bisanti Luigi Cadum Ennio Forsberg Bertil Forastiere Francesco Goodman Patrick G. Hojs Ana Kirchmayer Ursula Medina Sylvia Paldy Anna Schindler Christian Sunyer Jordi Perucci Carlo A. 1 3 2009
179 5 383 389 1073-449X 10.1164/rccm.200802-217oc 10.1164/rccm.200802-217oc
Heat-related emergency hospitalizations for respiratory diseases in the Medicare population American Journal of Respiratory and Critical Care Medicine Anderson G. Brooke Dominici Francesca Wang Yun McCormack Meredith C. Bell Michelle L. Peng Roger D. 15 5 2013
187 10 1098 1103 1073-449X 10.1164/rccm.201211-1969oc 10.1164/rccm.201211-1969oc 23491405
Heat Stroke Chest Sprung Charles L. 4 1980
77 4 461 462 0012-3692 10.1378/chest.77.4.461 10.1378/chest.77.4.461 7357963
Components and mechanisms of thermal hyperpnea Journal of Applied Physiology White Matthew D. 8 2006
101 2 655 663 8750-7587 10.1152/japplphysiol.00210.2006 10.1152/japplphysiol.00210.2006 16565352
The mechanism of exercise-induced asthma is … Journal of Allergy and Clinical Immunology Anderson Sandra D. Daviskas Evangelia 9 2000
106 3 453 459 0091-6749 10.1067/mai.2000.109822 10.1067/mai.2000.109822 10984363
Effect of temperature on cystic fibrosis lung disease and infections: a replicated cohort study PLoS One Collaco Joseph M. McGready John Green Deanna M. Naughton Kathleen M. Watson Christopher P. Shields Timothy Bell Scott C. Wainwright Claire E. for the ACFBAL Study Group, Garry R. Cutting3 18 11 2011
6 11 e27784 1932-6203 10.1371/journal.pone.0027784 10.1371/journal.pone.0027784 22125624
Verification of a Motion Sensor for Evaluating Physical Activity in COPD Patients Canadian Respiratory Journal Miyamoto Seiko Minakata Yoshiaki Azuma Yuichiro Kawabe Kazumi Ono Hideya Yanagimoto Ryuta Suruda Tadatoshi 2018
2018 8343705 1 8 1198-2241 10.1155/2018/8343705 10.1155/2018/8343705 29849834
Validation of a compact motion sensor for the measurement of physical activity in patients with chronic obstructive pulmonary disease Respiration Sugino Akihito Minakata Yoshiaki Kanda Masae Akamatsu Keiichiro Koarai Akira Hirano Tsunahiko Sugiura Hisatoshi Matsunaga Kazuto Ichinose Masakazu 9 9 2011
83 4 300 307 0025-7931 10.1159/000330046 10.1159/000330046 21912085
Methodology for using long-term accelerometry monitoring to describe daily activity patterns in COPD COPD: Journal of Chronic Obstructive Pulmonary Disease Hecht Ariel Ma Shuyi Porszasz Janos Casaburi Richard COPD Clinical Research Network 1 2009
6 2 121 129 1541-2555 10.1080/15412550902755044 10.1080/15412550902755044 19378225
Physical Activity Monitoring in Patients with Chronic Obstructive Pulmonary Disease Chronic Obstructive Pulmonary Diseases: Journal of the COPD Foundation Liao Shu-Yi Benzo Roberto Ries Andrew L Soler Xavier 2014
1 2 155 165 2372-952X 10.15326/jcopdf.1.2.2014.0131 10.15326/jcopdf.1.2.2014.0131 28848818
Patient-reported dyspnea in COPD reliability and association with stage of disease Chest Mahler Donald A. Ward Joseph Waterman Laurie A. McCusker Corliss ZuWallack Richard Baird John C. 12 2009
136 6 1473 1479 0012-3692 10.1378/chest.09-0934 10.1378/chest.09-0934 19696126
Evaluation of the Modified Medical Research Council Dyspnea Scale for Predicting Hospitalization and Exacerbation in Japanese Patients with Chronic Obstructive Pulmonary Disease Internal Medicine Natori Hiroki Kawayama Tomotaka Suetomo Masashi Kinoshita Takashi Matsuoka Masanobu Matsunaga Kazuko Okamoto Masaki Hoshino Tomoaki 2016
55 1 15 24 0918-2918 10.2169/internalmedicine.55.4490 10.2169/internalmedicine.55.4490 26726080
Internet, phone, mail, and mixed-mode surveys: The Tailored Design Method Dillman D.A. Christian L.M. Smyth J.D. Wiley Hoboken, NJ 2014

Chapter 4 - Epidemiological concepts in environmental epigenetics Environmental epigenetics in toxicology and public health Fry R C Academic Press 2020
89 105 10.1016/b978-0-12-819968-8.00004-4 10.1016/b978-0-12-819968-8.00004-4
COPD Overlap Syndromes: Asthma and Beyond Chronic Obstructive Pulmonary Diseases: Journal of the COPD Foundation Lambert Allison A. Dransfield Mark T. 2016
3 1 459 465 2372-952X 10.15326/jcopdf.3.1.2015.0176 10.15326/jcopdf.3.1.2015.0176 28848867
Research Priorities in Pathophysiology for Sleep-disordered Breathing in Patients with Chronic Obstructive Pulmonary Disease. An Official American Thoracic Society Research Statement American Journal of Respiratory and Critical Care Medicine Malhotra Atul Schwartz Alan R. Schneider Hartmut Owens Robert L. DeYoung Pamela Han MeiLan K. Wedzicha Jadwiga A. Hansel Nadia N. Zeidler Michelle R. Wilson Kevin C. Badr M. Safwan 1 2 2018
197 3 289 299 1073-449X 10.1164/rccm.201712-2510st 10.1164/rccm.201712-2510st 29388824
