
==== Front
Gerontology
Gerontology
GER
GER
Gerontology
0304-324X
1423-0003
S. Karger AG Basel, Switzerland

38861937
539753
10.1159/000539753
Clinical Section: Research Article
Epidemiology of Faecal Incontinence for People with Dementia Living in the Community in New Zealand: A Retrospective Cohort Study Using interRAI Home Care Assessment Data
Epidemiology of Faecal Incontinence with Dementia
2744638
Burholt Vanessa a b
2744639
Pillai Avinesh c
2744640
Cheung Gary d
2744641
Awatere Sharon Aroha e
2744642
Daltrey Julie e
a School of Nursing/School of Population Health, Waipapa Taumata Rau, The University of Auckland, Auckland, New Zealand
b Centre for Innovative Ageing, Swansea University, Swansea, UK
c Department of Statistics, Waipapa Taumata Rau, The University of Auckland, Auckland, New Zealand
d Department of Psychological Medicine, Waipapa Taumata Rau, The University of Auckland, Auckland, New Zealand
e School of Nursing, Waipapa Taumata Rau, The University of Auckland, Auckland, New Zealand
Correspondence to: Vanessa Burholt, vanessa.burholt@auckland.ac.nz
11 6 2024
9 2024
70 9 930939
9 2 2024
6 6 2024
2024
© 2024 The Author(s). Published by S. Karger AG, Basel
2024
https://creativecommons.org/licenses/by-nc/4.0/ This article is licensed under the Creative Commons Attribution-NonCommercial 4.0 International License (CC BY-NC) (http://www.karger.com/Services/OpenAccessLicense). Usage and distribution for commercial purposes requires written permission.
Abstract

Introduction

Globally, there are few studies but wide variation in the epidemiology of faecal incontinence (FI) for people living with dementia in the community. Our objectives are to identify 1-year period prevalence, 5-year incidence, and risks for FI for people living with dementia.

Methods

A retrospective cohort study comprising the International Residential Assessment Instrument Home Care version (interRAI‐HC) assessments in a 5-year period in New Zealand (N = 109,964). For prevalence analysis, we selected a dementia cohort for a 1-year period from August 1, 2020, to July 31, 2021 (n = 7,775). For the incidence analysis, participants in the dementia cohort were followed up from the day of the first dementia diagnosis during the period August 1, 2016, and July 31, 2021. Dementia was identified by combining diagnosis of “Alzheimer’s disease” and “Dementia other than Alzheimer’s disease.” Participants were coded with faecal incontinence if they were continent with a stoma, seldom incontinent, occasionally incontinent, often incontinent and incontinent.

Results

One year period (1 August 2020-31 July 2021) prevalence of FI was 26.7% (2,082/7,775) of people with dementia. 5-Year incident FI rate was 19.0 per 100 person-years for people with dementia and 12.3 per 100 person-years for people without dementia. Controlling for risk factors for FI in both groups the hazard ratio for FI was 1.7 for people with dementia.

Conclusion

FI affects a significant proportion of people with dementia in New Zealand. interRAI-HC data could facilitate global epidemiological studies to estimate service or intervention needs for people with dementia to redress or manage FI.

Plain Language Summary

Dementia is the largest single contributor to disability and need for care among older adults. Dementia is accompanied by a progressive decline in cognitive abilities that interferes with the performance of activities of daily living, including toileting. Caregivers rate the independent use of the toilet as the most important activity that they would like the person living with dementia to retain. Faecal incontinence affects the quality of life, causes caregiver strain and is often likely to contribute to moving the person with dementia into a care home. However, there are currently no robust estimates of how many people with dementia living in the community (not in a care home) also experience faecal incontinence. Using a national dataset (interRAI-HC) from New Zealand, we demonstrate that during 1 year (August 2020 to July 31, 2021) 26.7% of people living with dementia faced the additional challenge of faecal incontinence. Over a 5‐year period (August 2016 to July 2021) the risk of developing faecal incontinence for people living with dementia was 1.7 times greater than the risk for people without dementia. Our study demonstrates that faecal incontinence affects a significant proposal of older people with dementia who are living in the community in New Zealand. Globally, more than 35 countries collect the same data as used in this study. We argue, that this could be used internationally, to better understand the level of community, health and clinical services that are required to support people with dementia and their caregivers to manage faecal incontinence.

Keywords

Faecal incontinence
Toilet use
Activities of daily living
Prevalence
Dementia
This work was supported by the Health Research Council of New Zealand (Grant No. 21/117). The sponsor had no role in the conceptualisation, writing, or publication of this work.
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pmcIntroduction

There were an estimated 69,713 people living with dementia in New Zealand in 2020. It is anticipated that this number will increase to 167,483 by 2,050, including 12,030 Māori (Indigenous people of New Zealand) [1]. More than 50 million people live with dementia worldwide, and its prevalence will increase to 152 million in 2050 [2]. Dementia has frequently been described in terms of its global financial burden [3] with the costs primarily falling on families rather than health or long-term care sectors [4, 5]. Providing unpaid support and care for a person living with dementia in the community can be rewarding, however, there are also often negative effects which are referred to as caregiver burden [6]. Major risks for increased caregiver burden are declines in functional status and independence in basic activities of daily living (ADL) of the care-recipient living with dementia [6].

Caregivers have rated independent toilet use as the most important ADL for the person living with dementia to retain [7]. Caregivers supporting a person with incontinence (the involuntary loss of urine or faecal matter [8]) experience greater burdens than caregivers who do not manage incontinence [8]. Incontinence and dementia can be stigmatising, affecting self-image and quality of life [9, 10] and distressing for people living with dementia and their caregivers. People with dementia have greater rates of entry into residential care than older people without dementia and incontinence is a significant predictor of admission to residential care within this population [11]. Together this evidence suggests that interventions that help caregivers promote continence or manage incontinence may reduce the financial and social costs associated with dementia, by delaying entry into residential care and/or relieving caregiver stress associated with managing continence issues for people living with dementia in the community. Despite potential gains, a recent critical review noted a dearth of research in this field [12].

FI is a particularly debilitating condition for which older people are often reluctant to seek help [13, 14]. There are few studies that have estimated prevalence of FI for people with dementia living in the community. Overall, in studies (conducted since 2005) suggest a prevalence of FI between 0 and 27% [15–17]. The large range in prevalence is likely due to differences in the definitions and measurement of FI (e.g., type of stool and frequency of episodes) and cognitive impairment or dementia, methods of data collection, and small sample sizes [12, 18]. Despite dementia being a risk for FI [18], there are very few incidence studies. In the UK, the rate of a first diagnosis of FI in a primary care setting was three times higher for people with dementia than for those without dementia [19].

We urgently need to draw attention to the extent of the challenge posed by FI by increasing the volume of research in this area. One method to rapidly map community epidemiology is to draw on routinely collected data. The interRAI Home Care Assessment System (interRAI-HC) is a comprehensive geriatric assessment with good inter-rater reliability [20]. The interRAI-HC is part of the integrated interRAI assessment system. This is a comprehensive suite of 19 instruments including a common core set of approximately 70 items. These items cover areas such as activities of daily living, cognitive skills, mood, behaviour problems, falls, and health symptoms. There are also unique items specific to each instrument. Nine of the instruments are tailored for older people, facilitating the collection of comparable assessment information across various care settings. The inteRAI-HC is used in 35 countries to plan care and services for older people in community-based settings; it is mandatory in Canada, New Zealand, and Ireland, and is used research studies within Europe [20].

In New Zealand, an interRAI-HC assessment is mandatory for all older people who require public funding and services in the community. Health professionals or non-professionals involved in the care of an older person can make a referral for an assessment. Trained assessors conduct the assessments. For people deemed eligible for services, appraisals are repeated every 6 months or more frequently if a change in need for support is identified. In this article, we examine the prevalence, incidence, and risks for FI among people with dementia in the community who have had an interRAI-HC assessment in New Zealand, regardless of whether they subsequently received community health services.

Methods

Study Design and Data Source

We conducted a retrospective cohort study using administrative data collected using the interRAI-HC instrument, comprising 236 items in more than 20 domains including physical, mental, social, and cognitive domains of health. Technical Advisory Services (TAS) interRAI data warehouse provided interRAI-HC data completed anywhere in New Zealand between August 1, 2016, and July 31, 2021, and for all older people (65+ years) that had consented for their data to be used for research. There were assessments for 109,964 unique individuals during the 5-year study period (shown in Fig. 1).

Fig. 1. Flowchart of the study sample.

Study Cohorts

Dementia and non-dementia cohorts were identified using the diagnosis of “Alzheimer’s disease” and “Dementia other than Alzheimer’s disease” that are routinely recorded in an interRAI-HC assessment [21]. We combined these two diagnoses as one diagnostic category “Dementia.”

Cohort Entry and Exit

For the prevalence analysis, we selected a dementia cohort for a 1-year period from August 1, 2020, to July 31, 2021 (n = 7,775). For the incidence analysis, participants in the dementia cohort were followed up from the day of the first dementia diagnosis during the period August 1, 2016 and July 31, 2021. The non-dementia cohort comprised all eligible older people without a dementia diagnosis during the 5-year period and was followed up from the first assessment during the 5-year study period. For both cohorts, participants with no follow-up assessment and prevalent FI (i.e., FI recorded on the first assessment during the 5-year period) were excluded from the analysis. All participants exited the study on the date of their last assessment or July 31, 2021.

Primary Outcome

The primary outcome FI was measured in interRAI-HC, section H3 (continent, continent with a stoma, seldom incontinent [not incontinent during the last 3 days, but has episodes of incontinence], occasionally incontinent [more seldom than daily], often incontinent [daily, but has some control], incontinent [no control], and did not occur [absence of bowel movement during the past 7 days]). For the univariate and multivariable analyses, participants were re-coded as “incontinent” if they were continent with a stoma, seldom incontinent, occasionally incontinent, often incontinent, and incontinent. A decision to include “continent with a stoma” as incontinent was informed by the role that caregivers (to people with dementia) would likely have relating to ostomy care and the disposal of faecal matter [22]. Participants rated as “absence of bowel movement during the past 7 days” were coded as continent, which is consistent with other international studies using interRAI-HC data [23].

Co-Variates

Several potential risk factors that may predict the onset of FI assessed at baseline were investigated. These were selected based on evidence from previous studies of adult populations and availability within the interRAI-HC dataset and were grouped as socio-demographics (age [18, 24, 25], gender [18, 24], ethnicity [26]), lifestyle factors (physical exercise [25, 27], smoking [18, 25]), functional variables (independence in ADLs [18, 25]), comorbidities (depression [26], stroke [10], diabetes [10, 24], Parkinson’s disease [25], urinary incontinence [24, 28]) and environmental characteristics (access to rooms in the home [29]). Variables were coded as follows: age dichotomised at the median (equal or less than 83 years, equal or more than 84 years), gender (male, female), ethnicity (Māori vs. non-Māori, and Pacific vs. non-Pacific), hours of exercise dichotomised at the median (less than 1 h per week, equal to or more than 1–2 h per week), (usually) smokes tobacco daily (yes, no). Limited access to home or rooms in the home e.g., difficulty entering or leaving home, climbing stairs, or manoeuvring within rooms (yes, no). The six-item scale of hierarchy in ADLs (ranging from independence to complete dependence) was dichotomised as independent, and not independent. Comorbidities were indicated by a diagnosis (primary diagnosis, diagnosis with active treatment, diagnosis with no active treatment) versus no diagnosis for depression, stroke or cerebrovascular accident (CVA), diabetes and Parkinson’s disease (no, yes). Urinary incontinence was coded as continent (yes, no): categories (managed with catheter/ostomy, infrequently incontinent, occasionally incontinent, frequently incontinent, incontinent) were categorised as “no.”

Statistical Analysis

Logistic regression analyses were carried out in SPSS version 28 to determine the combination of risk factors that best predicted the incidence of FI. Univariate analyses were used to select variable associated with incident FI separately for the dementia and non-dementia cohorts. Variables that were significantly associated with the dependent variable (p < 0.25) were entered into multivariate logistic regression models and were removed using the Stepwise Backward Selection process (Wald statistic) until only significant variables (p < 0.05) remained in the models [30]. Survival curves (that is, months in the study without FI) of the dementia cohort versus the non-dementia cohort were compared with Cox regression analysis, adjusted for all variables which were significantly associated with incident FI in either cohort in the multivariate logistic regression models.

Results

Sample Characteristics

A total of 20,759 people without dementia and 7,722 people with dementia were included in the 5-year incidence study (shown in Fig. 1). The mean age of all participants (N = 28,481) was 82.2 years (SD: 7.5). A majority (20,865/28,481, 73.3%) of the sample were of New Zealand European ethnicity, 6.0% (1,715/28,481) identified as Māori, 3.4% (977/28,481) as Pacific Peoples and 3.1% (894/28,481) as Asian, 14.1% (4,030/28,481) identified with other ethnicities. The mean age of participants in the dementia and non-dementia cohorts was 80.9 years (SD 6.8) and 82.6 years (SD 7.7), respectively. Compared to the non-dementia cohort, a significantly greater proportion of the dementia cohort were male (χ12 = 103.1, p < 0.001), Māori (χ12 = 33.3, p < 0.001), ADL dependent (χ12 = 497.3, p < 0.001), and had a diagnosis of depression (χ12 = 24.9, p < 0.001). A significantly greater proportion of the non-dementia cohort were 84+ years (χ12 = 318.9, p < 0.001), had limited access to rooms in the home (χ12 = 94.2, p < 0.001), exercised less than 1 h per week (χ12 = 450.6, p < 0.001), a diagnosis of stroke or CVA (χ12 = 126.9, p < 0.001), Parkinson’s disease (χ12 = 17.4, p < 0.001), or diabetes (χ12 = 85.4, p < 0.001), or experienced urinary incontinence at baseline (χ12 = 138.0, p < 0.001) compared to the dementia cohort (shown in Table 1).

Table 1. Sample characteristics

	Dementia cohort, N (%) (N = 7,722)	Non-dementia cohort, N (%) (N = 20,759)	p valuea	
Sociodemographic	
 Age (84+ years)	29,33 (38.0)	10,350 (49.9)	<0.001	
 Gender (male)	3,396 (44.0)	7,758 (37.4)	<0.001	
 Ethnicity (Māori)	568 (7.4)	1,147 (5.5)	<0.001	
 Ethnicity (Pacific)	283 (3.7)	694 (3.3)	0.185	
Lifestyle	
 Exercise (<1 h per week)	3,775 (48.9)	13,037 (62.8)	<0.001	
 Smoking (daily)	351 (4.5)	1,052 (5.1)	0.07	
Function	
 ADLs (not independent)	2,869 (37.2)	4,958 (23.9)	<0.001	
Co-morbidity	
 Depression	1,141 (14.8)	2,601 (12.5)	<0.001	
 Stroke/CVA	873 (11.3)	3,467 (16.7)	<0.001	
 Diabetes	1,268 (16.4)	4,432 (21.3)	<0.001	
 Parkinson’s disease	282 (3.7)	997 (4.8)	<0.001	
 Urinary incontinence	2,398 (31.1)	8,012 (38.6)	<0.001	
Environment	
 Limited access to rooms	356 (4.6)	1,643 (7.9)	<0.001	
ADL, activities of daily living; CVA, cerebrovascular accident.

a p value from χ2 tests.

Incidence and Prevalence of Faecal Incontinence for People with Dementia

The total observation time was 126,789 months (10,565.8 years) for the dementia cohort and 409,196 months (34,099.7 years) for the non-dementia cohort. In the 5-year period, FI was acquired by 2,008 people with dementia and 4,176 older people without dementia. Thus, FI incidence rate was 19 per 100 person-years for people with dementia. This was greater than the incidence of FI in older people without dementia (12.3 per 100 person-years) (shown in Fig. 1). The 12-month period prevalence of FI was 26.7% (2,082/7,775) of people with dementia who had an interRAI-HC assessment.

Risk Factors for Faecal Incontinence and Survival

Odds ratios and 95% confidence intervals (CI) for variables that were significantly associated with incident FI (p < 0.05) in the univariate and multivariate logistic regression models for the non-dementia and dementia cohorts are shown in Table 2. Variables associated with a greater risk of incident FI in the multivariate logistic regression models for both cohorts were being male, exercising less than 1 h per week, not independent in ADLs, having a diagnosis of Parkinson’s disease and presence of urinary incontinence; for the dementia cohort were of Pacific ethnicity; and for the non-dementia cohort were having a diagnosis of diabetes, stroke, or CVA. Protective factors were smoking (for the dementia cohort), and Māori ethnicity (for the non-dementia cohort).

Table 2. Independent risk factors for incident FI in dementia and non-dementia cohorts

	Dementia cohort	Non-dementia cohort	
univariate logistic regression model FI	multivariate logistic regression model FI	univariate logistic regression model FI	multivariate logistic regression model FI	
OR (95% CI)	OR (95% CI)	OR (95% CI)	OR (95% CI)	
Sociodemographic	
 Age (84+ years)	1.1 (0.99–1.2) p = 0.075		1.1 (0.98–1.1) p = 0.156		
 Gender (male)	1.3 (1.2–1.4) p < 0.001	1.3 (1.2–1.4) p < 0.001	1.3 (1.2–1.4) p < 0.001	1.3 (1.2–1.4) p < 0.001	
 Ethnicity (Māori)	1.0 (0.8–1.2) p = 0.897		0.9 (0.7–1.0) p = 0.043	0.8 (0.7–0.94) p = 0.006	
 Ethnicity (Pacific)	1.6 (1.2–2.0) p < 0.001	1.4 (1.1–1.8) p = 0.009	1.0 (0.8–1.2) p = 0.893		
Lifestyle	
 Exercise (<1 h per week)	1.5 (1.3–1.6) p < 0.001	1.3 (1.2–1.4) p < 0.001	1.2 (1.1–1.3) p < 0.001	1.1 (1.1–1.2) p < 0.001	
 Smoking (daily)	0.7 (0.6–1.0) p = 0.023	0.7 (0.6–0.9) p = 0.021	1.0 (0.9–1.2) p = 0.615		
Function	
 ADLs (not independent)	1.9 (1.7–2.1) p < 0.001	1.6 (1.5–1.8) p < 0.001	1.7 (1.5–1.8) p < 0.001	1.5 (1.4–1.6) p < 0.001	
Co-morbidity	
 Depression	0.9 (0.8–1.0) p = 0.083		1.0 (0.9–1.1) p = 0.885		
 Stroke/CVA	1.1 (0.6–1.3) p = 0.141		1.2 (1.1–1.3) p < 0.001	1.1 (1.0–1.2) p = 0.025	
 Diabetes	1.3 (1.1–1.4) p = 0.001		1.3 (1.2–1.4) p < 0.001	1.2 (1.1–1.3) p < 0.001	
 Parkinson’s disease	1.7 (1.3–2.2) p < 0.001	1.3 (1.0–1.7) p = 0.045	1.3 (1.2–1.6) p < 0.001	1.2 (1.0–1.4) p = 0.029	
 Urinary incontinence	1.9 (1.8–2.2) p < 0.001	1.7 (1.5–1.9) p < 0.001	1.5 (1.4–1.7) p < 0.001	1.5 (1.4–1.6) p < 0.001	
Environment	
 Limited access to rooms	1.3 (0.99–1.6) p = 0.057		1.3 (1.1–1.4) p < 0.001		
ADL, activities of daily living; CVA, cerebrovascular accident.

Survival Function for Non-Dementia and Dementia Cohorts for Incident FI

In Cox regression analysis, the incident FI model was controlled for gender, ethnicity (Māori and Pacific), smoking, level of exercise, independence in ADLs, stroke or CVA, diabetes, Parkinson’s disease, and UI at baseline. People with dementia had a 1.7 higher risk of developing FI (HR adjusted for risk factors: 1.7, 95% CI: 1.6–1.8) than older people without dementia. The survival curves (that is, months in the study without FI) for dementia and non-dementia cohorts are shown in Figure 2.

Fig. 2. Survival function for non-dementia (n = 20,759) and dementia (n = 7,722) cohorts for incident FI.

Discussion

In this study, we found that the 12-month period prevalence of FI was 26.7% (2,082/7,775) for people with dementia in the community who had an interRAI-HC assessment. This is towards the upper end of the range for prevalence of FI indicated in other community studies (0–27%) [15–17]. Extrapolated to the estimated population of people with dementia living in the community in New Zealand (N = 69,713) [1], 18,480 may have experienced FI in 2020/2021. This may be an over-estimation as an interRAI-HC assessment is undertaken where there is a perceived need for support from home or health care services. This means that the sample of older people receiving assessments is not representative of the general population. However, the 12-month period prevalence for people with dementia assessed for care and support, is likely more robust than previous studies in Hong Kong, Republic of Ireland, and Turkey that were based on small convenience samples of participants (ranged from 82 to 197), drawn from dementia associations or geriatric out-patient clinics [15–17].

The incidence of FI was 19 per 100 person-years for people with dementia and 12.3 per 100 person-years for older people without dementia. Controlling for significant factors, people with dementia had a 1.7 higher risk of developing FI than older people without dementia. While the latter result is consistent with a study that indicated an increased hazard ratio of FI for people with dementia when compared to people with cancer [31], incident FI for people with dementia was much greater than observed in the UK: 11.1 for men and 10.1 for women per 1,000 person-years. Differences may be due to variations in the mean age and composition of samples: the UK sample comprised all older people (60+ years) registered with 500 General Practices in one region, whereas the interRAI dataset comprised a subset of older people (65+ years) assessed for care and support at home in New Zealand. It is also conceivable that differences are related to under-reporting of FI and the adage “if you don’t ask, they won’t tell” [32].

Studies of general populations have indicated that only a minority of people with FI (5–27%) disclose the stigmatised condition to their general practitioners [32]. We found UI significantly increased the risk of FI for people with dementia (OR = 1.7, 95% CI: 1.5–1.9), but elsewhere, it has been noted that there is less disclosure of FI for people experiencing dual incontinence [33]. In Spain, introducing FI screening into a diagnostic tool used by nurses identified three times the number of people with FI within 16 months compared to the number that had been identified in the previous 3 years. The greater rate of incident FI for people with dementia in New Zealand may be due to the direct questions incorporated into the interRAI-HC assessment, whereas an absence of routine screening in primary care practices coupled with the reluctance to report FI [18] may have contributed to the lower incidence rates captured by UK data.

In the multivariate analysis, smoking appeared to have a protective effect reducing FI for people with dementia (OR = 0.7, 95% CI: 1.2–1.5). This finding could be detrimental to public health and should be viewed with extreme caution. Even if smoking did offer a protective effect, this is unlikely to outweigh the adverse health effects of smoking.

Multivariate analysis showed that the risk of developing FI for people with dementia was greatest for those who were dependent in ADLs (OR = 1.6, 95% CI: 1.5–1.8), had a diagnosis or Parkinson’s disease (OR = 1.3, 95% CI: 1.0–1.7), experienced urinary incontinence (OR = 1.7, 95% CI: 1.5–1.9), or were of Pacific ethnicity (OR = 1.4, 95% CI: 1.1–1.8). The first three factors have been reported previously as risk factors for FI in adult populations [18, 24, 25], but to our knowledge, these factors, along with Pacific ethnicity have yet to be identified as specific risks for FI for people with dementia.

Constipation is prevalent in more than 50% of people with Parkinson’s disease and is also recognised as a prodromal symptom of the disease [34]. Although, a study has indicated that the presence of Parkison’s disease poses a greater risk of constipation, but not a greater risk of FI [35], severe constipation with faecal impaction may lead to overflow FI [18]. Others have noted that people with a neurological disease such as Parkinson’s disease often encounter other problems such as reduced rectal sensation which may precede FI [36]. The present study suggests that the combination of Parkinson’s disease and dementia increase the risk for FI, and that this group may benefit from targeted intervention.

Dependency in ADLs is an indicator of functional limitations. The increased risk of FI for people with dementia who exercise less than 1 h per week (OR = 1.3, 95% CI: 1.2–1.5) is also consistent with this finding. Together these factors suggest that some of the increased risk of FI is associated with functional impairment and reduced ability to reach a toilet in a timely way [25]. Additionally, physical activity plays a role in the neuromuscular health affecting anorectal function [27]. Thus, improving mobility through physiotherapy, occupational therapy, or environmental interventions may reduce the risk of FI for people with dementia [37].

In the multivariate model, Māori ethnicity was protective of FI for the non-dementia cohort but not for the dementia cohort. Research examining the barriers to diagnosing colorectal cancer suggested that privacy and cultural safety of health services were appraised by Māori when considering whether symptoms such as diarrhoea and changes in bowel habit warranted medical investigation [38]. The results of our study may suggest lower reporting in the non-dementia cohort in which older Māori may prefer to deal with FI privately. On the other hand, FI coupled with dementia was reported at a similar rate to the non-Māori cohort suggesting that for this population, incontinence cannot be managed privately.

We have outlined some of the limitations of this analysis above. The New Zealand sample is not a general community sample, but a sample of people who have health care support needs and have undertaken an interRAI-HC assessment. About 10% and 40% of New Zealanders over the age of 65 and 85 years had an interRAI assessment, respectively. Despite this limitation, this is one of the largest studies exploring the incidence, prevalence and risks associated with FI for people with dementia. Moreover, because interRAI-HC is more likely to capture data from people with dementia (who may be less inclined or able to participate in surveys), the findings may be more representative of this particular cohort than smaller convenience samples used in previous analyses [15–17]. The routine data collected via interRAI instruments has high validity, reliability, and low rates of missing data which can be considered a strength of this paper.

Conclusion

Health professionals need to be aware of the increased risk of FI for people with dementia. As differences observed between incident FI in the UK and New Zealand may be due to variations in eliciting information from direct questioning rather than relying on self-initiated disclosure, we suggest that health professionals should be prepared to initiate conversations about FI with people with dementia and their caregivers. The prevalence of FI and potential modifiable nature of some of the risk factors for incident FI, suggest that more research is required to demonstrate to policy makers and planners the extent of this challenge. The interRAI-HC datasets potentially provide a cost-effective means of identifying dementia and incontinence in retrospective cohort studies [39]. Further international analyses will be valuable to predict the level of service or interventions required to delay residential care entry, or to model future costs of continence care for people with dementia in the community.

Acknowledgements

We would like to thank Peter Tang, Data Analyst, and Costa Karavias, Senior Analyst, at TAS for their support in retrieving the interRAI data.

Statement of Ethics

This research study and the secondary analysis of de-identified interRAI data were reviewed and approved by Auckland Health Research Ethics Committee [AH23238]. Additionally, approval was provided by Technical Advisory Services to access the InterRAI dataset as authorised by Te Whatu Ora, Health New Zealand (https://www.interrai.co.nz/assets/Data/Data-Access-Protocols-December-2023.pdf). All interRAI assessments include a question about consent. Data included in the interRAI dataset were subject to participants’ verbal consent for planning and research purposes (https://www.interrai.co.nz/assets/Information-for-Researchers-to-Support-Ethics-and-Funding-Applications-June-2023.pdf).

Conflict of Interest Statement

The authors declare no conflicts of interest.

Funding Sources

This work was supported by the Health Research Council of New Zealand (Grant No. 21/117). The sponsor had no role in the conceptualisation, writing, or publication of this work.

Author Contributions

V.B. conceptualised and designed the study, performed the statistical analysis with the support of A.P. and G.C., and wrote the manuscript. A.P. and G.C. contributed to the methodology of the study. A.P., G.C., S.A., and J.D. contributed to the interpretation of the analysis and review and approval of the final manuscript.

Data Availability Statement

The administrative data supporting findings of this study are available from interRAI New Zealand but restrictions apply to the availability of these data. The interRAI data warehouse is administered by TAS and contains all records from the interRAI assessment in New Zealand. To apply for access to interRAI dataset(s), a requesting party must complete the process set out on the website www.interrai.co.nz.
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