
==== Front
BMC Public Health
BMC Public Health
BMC Public Health
1471-2458
BioMed Central London

39294642
19978
10.1186/s12889-024-19978-6
Research
Chinese version of the Physical Resilience Scale (PRS): reliability and validity test based on Rasch analysis
Dong Aohua
Zhang Huijun 13904069606@163.com

Kong Linghui
Lu Tingting
Zheng Chen
Ai Fangzhu
Feng Fuzhe
https://ror.org/02yd1yr68 grid.454145.5 0000 0000 9860 0426 Department of Nursing, Jinzhou Medical University, Jinzhou, LiaoNing China
18 9 2024
18 9 2024
2024
24 254111 10 2023
3 9 2024
© The Author(s) 2024
2024
https://creativecommons.org/licenses/by-nc-nd/4.0/ Open Access This article is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License, which permits any non-commercial use, sharing, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if you modified the licensed material. You do not have permission under this licence to share adapted material derived from this article or parts of it. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by-nc-nd/4.0/.
Background

Physical resilience is known to minimize the adverse outcomes of health stressors for older people. However, validated instruments that assess physical resilience in older adults are rare. Therefore, the purpose of this study was to translate the Physical Resilience Scale (PRS) into Chinese and to validate its psychometric properties in a population of community-dwelling older adults following SARS-CoV-2 infection.

Methods

This study used a cross-sectional design and translated the Physical Resilience Scale into Chinese. A total of 426 older adults who had recovered from SARS-CoV-2 infection were chosen for assessment through convenience sampling. The measurement data were analyzed using the Rasch analysis.

Results

Rasch analysis indicates that the Physical Resilience Scale demonstrates excellent reliability, validity, and unidimensionality. The Infit MNSQ and Outfit MNSQ of each entry were 0.77 ~ 1.19, and the degree of fit of each entry to the scale was good. Person and item separation reliability support the internal consistency of the studied samples and PRS items.

Conclusions

The Physical Resilience Scale has good reliability and is suitable for the assessment of physical resilience tests in older people. However, the overall difficulty of the scale is not suitable for older adults of all ability ranges, and it is possible to add higher and lower difficulty items and adjust the difficulty spacing between items in a later study.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12889-024-19978-6.

Keywords

Physical resilience
Scale
Reliability
Validity
Rasch analysis
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pmcBackground

The world has been experiencing unprecedented growth in the aging population. The population of people aged 80 years or older is expected to triple between 2020 and 2050 to reach 426 million [1]. The World Health Organization (WHO) has described this demographic shift as a major societal challenge and proposed 2021–2030 the decade of healthy aging, aiming to maintain optimum functional ability for older people throughout their life course [2]. However, maintaining one’s functional ability is not enough; recovering from injury, illness, or other health stressors that inevitably occur in a lifetime is crucial [3, 4]. An emerging concept stemming from this work is “physical resilience,” which is defined as the ability to recover or optimize function in the face of physical challenges (age-related losses or disease) such as degenerative joint disease, a hip fracture, or an acute medical event such as pneumonia. Indeed, healthy aging requires a life course approach, and improving physical resilience may attenuate the cascade of adverse outcomes associated with aging [5].

A better understanding of physical resilience may contribute to healthy aging. The National Institute on Aging in the United States has prioritized the development of instruments to objectively measure an individual’s level of physical resilience [3]. Assessing physical resilience typically involves subjecting individuals to experimental stressors to elicit measurable changes in internal equilibrium parameters, thereby determining their recovery capacity [6]. However, it is neither feasible nor ethical to expose older adults to such stressors. Therefore, this study aimed to investigate the physical resilience of older adults following SARS-CoV-2 infection [7]. The COVID-19 pandemic has posed a significant threat to global public health, particularly affecting older adults [7]. This demographic tends to exhibit compromised immune function, diminished resistance, and often suffers from multiple chronic conditions. Consequently, older adults are more susceptible to COVID-19, experiencing higher incidence rates, rapid disease progression, and increased mortality rates [8]. As such, they represent a critical target population for efforts to control and prevent the spread of the pandemic.

Physical resilience constitutes a fundamental component of recovery following significant physical stressors [9, 10]. The identification of individuals with notably low physical resilience, alongside the provision of targeted interventions to enhance resilience and aid in the recovery process, necessitates the use of reliable and valid measures. Extensive research on physical resilience conducted internationally has yielded well-established assessment tools [9, 11]. Various methodologies for assessing physical resilience have been explored, such as defining resilience by recovery phenotypes and expected recovery differentials, comparing the effects of dynamic stimulation tests before and after the evaluation of individual resilience, and monitoring changes in indicators like activities of daily living, the Short Form Health Survey (SF-36), the Short Physical Performance Battery (SPPB), and the deficit accumulation index [12–15]. Despite the efficacy of these methods, they typically demand prolonged dynamic observation periods. Furthermore, several resilience questionnaires, including the Resilience Scale (RS), the Resilience Scale for Older Adults (RSOA) [16], and the Physical Resilience Instrument for Older Adults (PRIFOR) [5], have been developed.

Nonetheless, the clinical application of these measures remains nascent, with certain scales failing to encompass all aspects of physical resilience comprehensively [14, 15]. Importantly, there exists a discernible gap in research focused on the physical resilience of older adults in mainland China. This study aims to validate the Chinese translation of the Physical Resilience Scale, undertake cross-cultural adaptation, and evaluate its reliability and validity. The validated scale will be employed to assess the physical resilience of older adults in the community who have endured acute health stressors, such as SARS-CoV-2 infection.

Methods

Study procedures

This study employed a cross-sectional design and utilized convenience sampling within the communities of Guta and Linghe districts in Jinzhou. The study was conducted in two phases. In the first phase, the PRS scale was translated into Chinese using a Delphi process to obtain expert opinion for content validity [17]. In the second phase, a convenience sample of elderly individuals was randomly selected from the community to test the validity and reliability of the scale. Adherence to the guidelines outlined in the Declaration of Helsinki was maintained throughout all phases of the study.

Study participants

The inclusion criteria for participants were: (1) age greater than 60 years; (2) older adults who had been infected with SARS-CoV-2; (3) As native speakers of Chinese, the participants could understand and complete the questionnaire. Exclusion criteria included: (1) older adults who have been diagnosed by a physician with cognitive impairment and are unable to complete scale surveys correctly and independently; (2) subjects who were already participating in a similar study. The study protocol received approval from the Ethics Review Committee of Jinzhou Medical University (approval number JZMULL2023087), and written informed consent was obtained from all participants prior to their participation in the study.

Research tools

General information questionnaire

A self-designed general information questionnaire was used to collect information on age, gender, ethnicity, literacy, marital status, current occupation, and monthly household income of the older adults.

Physical Resilience Scale (PRS)

The Physical Resilience Scale was developed by Resnick et al. in 2011 based on the characteristics of successful aging, including humor, social support, adaptability, and personal strengths [18]. The Physical Resilience Scale was originally developed as a 15-item measure and testing was done with older adults living in the community. The scale comprises 15 items, with scores generated by answering agree or disagree. A greater score indicates better physical resilience. The scale had a Cronbach’s alpha coefficient of 0.89 and a test-retest reliability of 0.73. It has previously been implemented in older adults with osteoarthritis and community-dwelling older adults. To obtain the original scale, the researchers sought permission from Professor Resnick, the original author, via email communication and subsequently began the process of translating it.

Geriatric Depression Scale (GDS-5)

The 5-item Geriatric Depression Scale (GDS-5) is used to evaluate depression levels in older adults [19]. The total score is obtained by summing the scores of the five items, with higher scores indicating more severe depression. The GDS-5 has demonstrated good internal consistency (α = 0.83–0.90), and its sensitivity is 0.94, specificity is 0.81, with a positive predictive value of 0.81 and a negative predictive value of 0.94. The scale also has a positive likelihood ratio of 4.92 and a negative likelihood ratio of 0.07.

Mini-mental State Examination (MMSE)

The Mini-Mental State Examination (MMSE) is used to evaluate participants’ cognitive function across five dimensions: orientation, memory, attention, calculation, and language, comprising a total of 30 items. Scores range from 0 to 30, with higher scores indicating better cognitive function [20]. It is important to note that the results may be influenced by the participant’s education level. The cutoff scores for identifying cognitive impairment are ≤ 17 for those without formal education, ≤ 20 for those with primary education, and ≤ 24 for those with junior high school education or higher.

Katz index of independence in Activities of Daily Living (Katz ADL)

The Katz Index of Independence in Activities of Daily Living (Katz ADL) evaluates functional abilities in daily activities such as bathing, dressing, toileting, transferring, eating, and managing incontinence [21]. Developed as both an observational and self-reported measure, each activity is rated from 0 to 2: a score of 0 signifies a need for extensive assistance, 1 indicates limited assistance, and 2 denotes independence. The cumulative score ranges from 0 to 12, with higher scores reflecting greater independence in daily living activities. The internal consistency of the Katz ADL has been confirmed, with a Cronbach’s alpha ranging from 0.84 to 0.94.

Physical Resilience Instrument for Older Adults (PRIFOR)

The PRIFOR assesses physical resilience in older adults after acute physical events or exacerbations. It contains 19 items scored on a 5-point Likert scale (1 = strongly disagree; 5 = strongly agree). The total score, reflecting physical resilience, is the sum of affirmative responses. The PRIFOR has a high internal consistency with a Cronbach’s alpha of 0.94, and it has demonstrated good criterion-related validity, known-group validity, and predictive validity.

Translation of the scale

After authorization was obtained from the original author, the Brislin translation-back-translation model was used to translate the English version of the Physical Resilience Scale [22]. ①Forward translation: The scale was translated from English into Chinese by three bilingual researchers whose native language is Chinese (all three are nursing Master’s students). The translations were named T1, T2, and T3. ②Synthesis: The research team members compared T1, T2, and T3 and selected the most appropriate expressions through discussion, forming a preliminary Chinese version named PRS-A. ③Back-translation: Two individuals (Master’s students) who had not been exposed to the original scale and had passed English Major Level 8 independently back-translated Chinese version (PRS-A) into two English versions named BT1 and BT2. After completion, the research team members compared, discussed, and modified BT1 and BT2, forming a preliminary back-translated version named PRS-B. The back-translated version of PRS-B was sent to the original scale author for evaluation of the consistency of content, semantics, and format between the back-translated version and the original version, resulting in the final Chinese version named PRS-B.

Cultural adaptation of the scale

The translated scale should not only conform to the culture and thinking of China but also not deviate from the original meaning of the scale. Therefore, cultural adaptation was necessary. In this study, seven experts were invited to carry out cultural adaptation of the Chinese version PRS-B. The inclusion criteria for the experts were as follows: ①Bachelor’s degree or above; ②Intermediate professional title or above; ③More than 10 years of relevant work experience and outstanding academic achievements in their field or discipline; ④Agreement to participate in this consultation. Among the seven experts, three were nursing professors or associate professors (specializing in geriatric nursing), two were nursing department directors, one was a head nurse, and one was an associate professor of English linguistics. The experts were asked to evaluate the readability of the items, the clarity of the concepts, the relevance of the items to their dimensions, the language expression habits, and the cultural background based on their professional knowledge and clinical work experience. The opinions of each expert were summarized and discussed by the research team members, and after modification, the final Chinese version named PRS-C was formed.

A convenience sampling method was employed to select 30 senior citizens from the Guta and Linghe districts of Jinzhou city. The Chinese version of the PRS-C questionnaire was utilized for a pre-survey to assess the content of the questionnaire. Data were collected on the difficulties encountered by the participants while completing the questionnaire. Researchers evaluated the participants’ understanding of the purpose or meaning of each question and recorded the time required to complete the questionnaire. The suggestions provided by the participants were thoroughly analyzed and summarized. These insights were then conveyed to experts for subsequent adjustments.

It was found that participants easily confused item 10 “I asked for help from others if I needed it” with item 9 “I accepted help from others”. The reason for including item 10 in the scale is that we have heard repeatedly from older adults that it is often difficult to ask for help when undergoing physical challenges. Therefore, the research team discussed retaining item 10 and rewriting the item to read, “When I need help, I actively seek help from others”. This emphasizes the fact that the elderly are spontaneous, active and positive in seeking help from the outside world. Instead of just passively waiting to receive help from others. The twelfth item, “I saw this challenge as an opportunity,” was asked by many older adults due to language and cultural differences, “What kind of opportunity do I see this challenge as?” To make it easier for older people to understand, the research team agreed to add “I see the challenge of illness as an opportunity to live a healthy life in the future”. Finally, the presurvey for item 13 (I was determined to regain my prior functional ability) revealed that many older adults did not understand this point, so to facilitate older adults’ understanding and response, the research team negotiated to add “I was determined to restore my physical function before my illness. restore my physical function before my illness.” Consequently, a finalized Chinese version of the PRS was developed, ensuring both clarity and comprehension for the respondents.

Data collection and measurements

The survey was conducted within the communities of Guta and Linghe districts in Jinzhou from January 2023 to October 2023. Data collection was conducted by the researchers, with assistance from other trained team members after training. Before the survey, the researchers obtained consent from community personnel and distributed questionnaires based on the community situation. The team explained the purpose and significance of the study to the participants before conducting the questionnaire survey with their consent. The survey questionnaires were collected at the site, and their data completeness was verified. Following the survey, the data were immediately arranged, and two individuals performed double-entry and checked for completeness and accuracy. Based on previous studies employing the Rasch model, an optimum sample size of 300–500 was identified for model adequacy [23–25]. Therefore, the study comprised 450 older people, with a final effective sample size of 426 and an effective response rate of 94.67%, meeting the sample size requirements for unidimensional Rasch analysis in Item Response Theory (IRT) [24, 26].

Data analysis

Descriptive statistics were conducted to illustrate the sample using SPSS 26.0. The model testing was performed through Rasch analysis using the Winsteps 3.66.0 statistical program [27]. In the Rasch analysis, we utilized the Dichotomous Model, as it was the most appropriate for the Physical Resilience Scale items, which were binary and each offered only two possible responses: Agree or Disagree. The Rasch analysis specifically examined unidimensionality, reliability analysis, item mapping, and fit statistics.

Validity analysis

The content validity evaluation was conducted by seven professionals utilizing the Delphi Expert Consultation approach [28, 29]. Each item was classified into four levels (ranging from inappropriate to appropriate), which were individually rated by each professional. The content validity index at the scale level (S-CVI) and the content validity index at the item level ( I-CVI) were used to evaluate the content validity of the scale [30]. The I-CVI value corresponds to the number of experts who scored 3 or 4 points, and it is divided by the total number of experts who participated in the assessment [31]. The S-CVI is obtained by calculating the average of the I-CVI value for each individual item [32].

We have assessed concurrent validity using both Item Response Theory (IRT) and Classical Test Theory (CTT) [33, 34]. In Rasch analysis, this was achieved by comparing the PT measures from the Rasch model with the scores from the gold standard measure (PRIFOR) [35, 36]. Based on Classical Test Theory (CTT), Pearson correlation coefficients were utilized to analyze the bivariate correlations between the Physical Resilience Scale (PRS) and external criteria measures (GDS-5, MMSE, and Katz ADL) to determine concurrent validity [37]. This multi-perspective and multi-method validation further consolidates the validity of the PRS.

Reliability analysis

Rasch analysis reliability refers to the ability to replicate the individual and item positions along the trait continuum. Person reliability assesses whether a measure can effectively differentiate individuals across a range of levels, while item reliability measures how accurately the sample can place items on a latent variable. High levels of person or item reliability indicate a greater likelihood that individuals or items obtaining higher scores truly possess higher proficiency than those with lower scores. The person separation index categorizes individuals, and a low separation score implies that the measure cannot distinguish between those who exhibit high and low ability. The item separation index affirms the item hierarchy, and a low separation score indicates that the sample is insufficient to substantiate the item difficulty hierarchy of the scale.

Item fit

Item fit was assessed for each item using INFIT and OUTFIT statistics obtained from Winsteps software [38]. A range of 0.5 to 1.5 indicates a satisfactory fit of the item to the measurement model [39]. Fit statistics were determined by calculating the mean-square, which is the result derived by dividing the chi-square statistic by degrees of freedom. Values greater than 1.5 (under fit) indicate unexplained variance in the data, while values less than 0.5 (over fit) indicate that the responses are too predictable and that the item does not add any new information [38]. A good fit of the item to the measurement model suggests that the item contributes to the concept being tested. An item may not fit because none of the participants endorse or agree with it.

Item mapping

Item mapping was conducted to assess the distribution of items across the entire range of physical resilience. An indication of the measure’s validity can be obtained when the mean item measure aligns with the mean person’s measure on the map, indicating that overall, the items align with the participants’ abilities [25, 38]. An indication of the measure’s validity can be obtained when the mean item measure aligns with the mean person’s measure on the map, indicating that overall, the items align with the participants’ abilities. This implies that the item difficulty level is a suitable match for the participants [27].

Results

Demographic information

A total of 426 community-dwelling older adults who had been infected with SARS-CoV-2 were included. Among them, there were 267 males (62.7%) and 159 females (37.3%). The age ranged from 60 to 93 years (68.24 ± 7.63). The educational level of the participants was as follows: 243 had a primary school education or below (57.0%), 126 had a middle school or high school education (29.6%), and 57 had a college education or above (13.4%). The marital status of the older adults was as follows: 357 were married (83.8%), 34 were divorced (8.0%), and 35 were widowed (8.2%). As shown in Table 1.

Table 1 Sample descriptive data

	N = 426	Frequency	N(%)	
Gender	Male	267	62.70	
Female	159	37.30	
Age	60–70	331	77.70	
71–80	84	19.70	
81–90	11	2.60	
Marriage	Married	357	83.80	
Divorced	34	8.00	
Widowed	35	8.20	
Education	Primary and below	243	57.00	
High School	126	29.60	
Bachelor degree and above	57	13.40	

Content validity

The content validity of the translated measure was assessed by seven experts who individually scored each item. The I-CVI range was 0.714-1.000 and the S-CVI value was determined to be 0.924, demonstrating that the translated measure had appropriate content reliability. For more details, please refer to Table 2.

Table 2 Item-level CVI for the Chinese version of the PRS

Items	Expert1	Expert2	Expert3	Expert4	Expert5	Expert6	Expert7	I-CVI	UA	
Q1	4	3	3	3	3	3	2	0.857	0	
Q2	4	2	4	4	4	4	3	0.857	0	
Q3	3	4	3	3	3	4	4	1.000	1	
Q4	3	4	1	4	2	4	3	0.714	0	
Q5	4	3	3	4	3	3	4	1.000	1	
Q6	4	2	4	3	4	3	3	0.857	0	
Q7	3	4	3	4	3	4	4	1.000	1	
Q8	4	3	3	3	4	3	4	1.000	1	
Q9	3	4	3	3	3	3	3	1.000	1	
Q10	4	3	4	3	3	3	3	1.000	1	
Q11	3	4	3	3	4	4	3	1.000	1	
Q12	4	3	2	4	3	3	4	0.857	0	
Q13	3	4	4	3	3	4	4	1.000	1	
Q14	3	3	4	4	3	4	3	1.000	1	
Q15	4	3	4	3	4	3	4	1.000	1	
S-CVI/Ave	0.943	
S-CVI/UA	0.667	

Concurrent validity

Concurrent validity involves comparing the scores of the Physical Resilience Scale (PRS) with the scores from the Physical Resilience Instrument for Older Adults (PRIFOR) taken at the same time [34]. In Rasch analysis, this is achieved by comparing the PT measures from the Rasch model with the scores from the PRIFOR. To assess concurrent validity, the correlation coefficient (Pearson’s r) between the PT measures obtained from the Rasch analysis of the PRS and the scores from the PRIFOR is computed [36]. In this study, the correlation between the PT measures of the PRS and the scores from the PRIFOR was found to be ( r = 0.768 ) with ( p < 0.001 ). A high correlation (typically ≥ 0.70 ) indicates good concurrent validity, suggesting that the PRS is a valid measure of physical resilience [36]. To ensure further testing of concurrent validity, this study also tested concurrent validity based on Classical Test Theory (CTT) in the Supplementary file. This multi-perspective and multi-method validation further consolidates the validity of the PRS [34].

Rasch model analysis

Unidimensionality test

Unidimensionality was examined to ensure that the scale measured a single latent trait, as needed for Rasch model analysis. This was done by performing a Principal Component Analysis (PCA) on the standardized residuals [40]. To validate the unidimensionality of the scale, a principal component analysis was performed on the standardized residuals. The results showed that the eigenvalue of the first component of the standardized residuals was 2.0. The unexplained variance of the eigenvalue for the first contrast should be less than 3.0 [40, 41], with a minimum ratio of 3:1 between the variance explained by the Rasch dimension and that of the first contrast, supporting its unidimensionality.

Item fit

The Rasch model necessitates the fulfillment of certain requirements for the collected data to be tested for congruity with the model. The primary evaluation indicators include the information-weighted fit statistic mean square (Infit MNSQ) and the outlier-sensitive fit statistic mean square (Outfit MNSQ) [38]. A value of MNSQ between 0.5 and 1.5 for each item is regarded as indicative of a good fit, with a value closer to 1 indicating a superior fit [39, 42]. The correlation between each item and its dimension is represented by the PT measure, with a value between 0.4 and 0.8 considered indicative of good correlation. When the MNSQ value exceeds the accepted range of 0.5–1.5, the standardized ZSTD is commonly reported, as it indicates a fit beyond the MNSQ range [39]. The study results demonstrate that the Infit MNSQ and Outfit MNSQ values of the unidimensional scale were between 0.5 and 1.5, indicating a satisfactory fit [43]. For more details, please refer to Table 3.

Table 3 Fit statistics for items on the physical resilience scale

Order	Item	INFIT	OUTFIT	PT	
		MNSQ	ZSTD	MNSQ	ZSTD	MEASURE	
1	I was determined to recover.	0.79	-3.60	0.77	-1.80	0.63	
2	I have adapted to the new changes brought about by the disease.	1.04	0.60	1.10	0.90	0.55	
3	I will use optimism to help myself through the difficult times.	1.00	-0.10	0.99	-0.10	0.59	
4	I believed I could recover.	1.01	0.20	1.05	0.50	0.56	
5	I focus on the things I can do, not the things I can’t do.	1.01	0.20	1.04	0.40	0.59	
6	I accepted the new challenges.	1.01	0.10	1.05	0.50	0.59	
7	I figured out how to do my daily activities.	1.07	1.20	1.07	0.70	0.57	
8	I have learned knowledge from my illness experience.	0.94	-0.90	0.93	-0.80	0.63	
9	I accepted help from others.	0.94	-1.10	0.89	-1.20	0.64	
10	If I need help, I will take the initiative to ask others for help.	1.05	0.90	1.19	1.90	0.58	
11	I found the energy to do what I have to do.	1.00	0.00	0.96	-0.40	0.60	
12	I see the challenge of illness as an opportunity to live a healthy life in the future.	1.03	0.40	1.04	0.40	0.61	
13	I was determined to restore my physical function before my illness.	1.01	0.10	0.77	-1.80	0.62	
14	I became a stronger person.	1.11	1.80	1.16	1.80	0.57	
15	I continued to make plans for the future.	0.92	-1.30	0.94	-0.70	0.65	
A value of MNSQ between 0.5 and 1.5 for each item is regarded as indicative of a good fit, with a value closer to 1 indicating a superior fit

Reliability and separation indices

In Rasch model analysis, a higher reliability and separation index indicates better scale and item-person separation [42]. The separation index measures how effectively the scale distinguishes individuals into distinct ability levels, or in this case, levels of resilience. The good person separation is ≥ 2.0. Person reliability of 0.70 to be regarded as acceptable, of 0.80 to be considered satisfactory and of 0.90 deemed as excellent [42]. The person separation for this study was 2.1 and person- reliability was 0.75. In addition, we further used Classical Test Theory (CTT) was used to determine the reliability of the scale and measured Cronbach’s alpha coefficient of 0.882. In this study, thirty participants were randomly selected from the total sample, and the PRS was administered twice. The intraclass correlation coefficient (ICC) for test-retest reliability was found to be 0.854, indicating good reliability [18, 43].

Differential item functioning analysis

Differential item functioning (DIF) analysis was conducted to examine whether respondents from a specific demographic group exhibited different response patterns compared to a reference group. It is possible that an item may prove to be more challenging or less likely to be endorsed by one group of individuals. DIF analysis (Table 4) showed that there was no variance in the items across gender. A DIF contrast value less than 0.5 logit is indicative of measurement invariance [41, 44]. These results demonstrate that the Physical Resilience Scale accurately measures distinct characteristics of the population.

Table 4 DIF analysis for physical resilience by gender

Person Classification	Scale Item	DIF Score	DIF
Measure	DIF Size	DIF SE	DIF
t	DIF Contrast	P	
Male	PR1	0.03	-0.91	-0.21	0.17	-1.20	-0.57	0.01	
Female	PR1	-0.06	-0.34	0.36	0.22	1.63	0.57	0.01	
Male	PR2	0.03	-0.71	-0.20	0.17	-1.21	-0.56	0.05	
Female	PR2	-0.06	-0.15	0.36	0.22	1.64	0.56	0.05	
Male	PR3	0.00	-0.13	0.00	0.16	0.00	0.00	0.93	
Female	PR3	0.00	-0.13	0.00	0.22	0.00	0.00	0.93	
Male	PR4	0.02	-0.63	-0.10	0.17	-0.61	-0.28	0.35	
Female	PR4	-0.03	-0.34	0.18	0.22	0.83	0.28	0.35	
Male	PR5	-0.01	-0.05	0.05	0.16	0.32	0.15	0.66	
Female	PR5	0.02	-0.20	-0.10	0.22	-0.44	-0.15	0.66	
Male	PR6	-0.03	0.05	0.17	0.16	1.06	0.49	0.08	
Female	PR6	0.05	-0.44	-0.32	0.22	-1.45	-0.49	0.08	
Male	PR7	-0.01	-0.05	0.07	0.16	0.42	0.20	0.33	
Female	PR7	0.02	-0.24	-0.13	0.22	-0.58	-0.20	0.33	
Male	PR8	-0.01	0.33	0.07	0.16	0.43	0.19	0.45	
Female	PR8	0.02	0.13	-0.13	0.22	-0.58	-0.19	0.45	
Male	PR9	-0.04	0.48	0.22	0.16	1.38	0.62	0.02	
Female	PR9	0.07	-0.15	-0.41	0.22	-1.87	-0.62	0.02	
Male	PR10	0.02	-0.07	-0.14	0.16	-0.87	0.39	0.13	
Female	PR10	-0.04	0.32	0.25	0.21	1.19	-0.39	0.13	
Male	PR11	-0.02	0.15	0.10	0.16	0.66	0.30	0.28	
Female	PR11	0.03	-0.15	-0.20	0.22	-0.90	-0.30	0.28	
Male	PR12	0.00	0.30	-0.20	0.16	-0.14	-0.06	0.73	
Female	PR12	-0.01	0.36	0.04	0.21	0.19	0.06	0.73	
Male	PR13	0.01	0.43	-0.06	0.16	-0.37	-0.17	0.45	
Female	PR13	-0.02	0.59	0.11	0.21	0.50	0.17	0.45	
Male	PR14	-0.01	0.35	0.04	0.16	0.28	0.13	0.43	
Female	PR14	0.01	0.23	-0.08	0.21	-0.38	-0.13	0.43	
Male	PR15	0.01	0.40	-0.05	0.16	-0.32	-0.15	0.50	
Female	PR15	-0.02	0.55	0.09	0.21	0.44	0.15	0.50	
DIF Score is the difference between the observed and the expected average observations. DIF Measure is the difficulty of the item for the category, with all else held constant. DIF Size is the difference between the DIF measure for a certain category and the baseline difficulty. DIF SE is the standard error of the second DIF measure. DIF t is the DIF contrast divided by the SE of the two DIF measures. It is equivalent to the Mantel-Haenszel significance test, but has the advantage of allowing missing data

Item-person matching

The Wrigh’s person-item map, also known as Wright Map, converts the raw scores of individual ability and item difficulty into logit values and puts them on the same scale, which visualizes the appropriateness of the items to the individual, and is one of the indicators of the overall quality of the scale [26]. The left side represents the distribution of the subjects’ ability and the right side represents the distribution of the difficulty value of the items, M is the mean value of the two sides, ideally, the M value of the two sides should be close to 0 and the difference should be < 1 logit, if the difference between the two mean values of the measure is > 1 logit, it usually means that there is a mismatch of the ability of the individual and the difficulty of the items [38]. The results of this study show that the overall fit between individual ability and entry difficulty is good and similarly distributed, indicating that the distribution of entry difficulty is more centralized and the distribution of individual ability is relatively broader; none of the differences in the measures of the mean values exceeds 1 logit (Fig. 1). However, the overall difficulty of the scale is not suitable for older adults of all ability ranges, and it is possible to add higher and lower difficulty items and adjust the difficulty spacing between items in a later study.

Fig. 1 Wrigh’s Person-item map for the Physical Resilience Scale

Note. Subjects are represented on the left of the dashed line by the symbol “#” (which represents 2 subjects) and “.” (which indicates 1 subject). On the right of dashed line are illustrated the items of the Physical Resilience Scale with their number. M indicates the mean measure (on the left the person ability and on the right the item difficulty). S shows one standard deviation from the mean and T denotes two standard deviations. The top of the figure shows objects and people with higher ability

Discussion

Previous research has predominantly employed Classical Test Theory (CTT) to demonstrate the psychometric properties of scales [33]. In contrast, our study utilizes an innovative psychometric approach, specifically Rasch analysis, to validate the Physical Resilience Scale (PRS) [45]. A robust assessment tool must be evaluated across diverse populations using various statistical methods. Employing the Rasch model for psychometric evaluation is essential due to its distinct advantages: (a) it allows for the individual analysis of item validity, thereby identifying redundancies that might be overlooked by CTT; (b) it separates the estimates of item difficulty and person ability; and (c) it provides an ordinal-to-interval conversion table, which enables healthcare professionals to interpret respondents’ latent traits more accurately [41].

Rasch analysis indicates that the Physical Resilience Scale (PRS) demonstrates excellent reliability, validity, and unidimensionality. The person and item separation reliability supports the internal consistency of the samples and PRS items, with the separation index showing that the samples and items span a broad range of physical resilience abilities and difficulties [46]. Previous psychometric evaluations of the PRS in older patients have confirmed its criterion-related validity, predictive validity, concurrent validity, and internal consistency [6, 18]. Our current findings align with previous research, affirming that the PRS is a valid instrument when assessed through various psychometric methods.

The model fit analysis confirms that the PRS meets the standards of Rasch model analysis. The majority of items had |T| < 2.0 in the item fit analysis, indicating they fall within the acceptable reference range [42]. This further validates that the scale measures a consistent construct and can predict memory self-efficacy in participants. The PT-measure correlations for each item, ranging from 0.55 to 0.65, fall within the standard range, highlighting strong correlations between the items and the overall scale. The analysis results indicate that all 15 items in the model fit analysis exhibited Infit MNSQ and Outfit MNSQ values within the range of 0.5–1.5, which demonstrates optimal fitting [26]. The PRS has shown good concurrent validity in older adults when compared to other measures of depression, cognition, and activities of daily living.

The PRS demonstrates robust validity. The content validity of the translated measure was assessed by seven experts who individually scored each item. The I-CVI ranged from 0.714 to 1.000, and the S-CVI was determined to be 0.924, illustrating that the translated measure had appropriate content validity. In this study, the PRS showed good concurrent validity, further suggesting that it is a valid measure of physical resilience. PRS scores were significantly negatively correlated with depression and positively correlated with cognition and activities of daily living, indicating that the scale content can accurately predict the level of physical resilience in participants.

The Physical Resilience Scale also exhibits strong reliability. Traditional measurement methods typically utilize Cronbach’s alpha coefficient as an indicator of a scale’s internal consistency reliability, with a coefficient exceeding 0.8 considered to reflect good reliability [33]. In this study, the PRS yielded a Cronbach’s alpha coefficient of 0.882, demonstrating good internal consistency reliability. The Rasch model analysis revealed an item reliability of 0.75 based on data-model fit analysis, suggesting acceptable reliability levels for the translated scale. The reliability of the PRS is corroborated by both Classical Test Theory (CTT) and Rasch analysis, further reinforcing its robustness.

The Wright map of the Physical Resilience Scale shows that the difficulty of the scale entries is evenly distributed, with entry 15 (I continued to make plans for the future) being the most difficult, and a large proportion of the older adults choosing to ‘agree’ and responding that they had no plans for the future; entry 1 (I was determined to recover) was the least difficult, and the vast majority of the senior citizens answered: “I do not have any plans for the future, I just take one step at a time”; entry 1 (I was determined to recover) was the least difficult, and the vast majority of the seniors chose to ‘agree’, and indicated that they had the determination to recover their health. Most of the subjects were evenly distributed in terms of ability concentration. This indicates that the difficulty of the scale corresponds well with the level of the subjects, and a small number of subjects’ physical resilience is beyond the difficulty range of the scale. The fact that most of the entries are of medium difficulty and a few are of higher or lower difficulty indicates that the scale applies people with average ability values and that there are not enough entries to target subjects with higher or lower ability.

The limitations of this study include the exclusive use of the Rasch model for scale validation, whereas contemporary international psychological measurement research frequently employs Classical Test Theory (CTT) as a standard reference. Future research should therefore aim to validate the scale using both CTT and Item Response Theory (IRT) to thoroughly investigate its scientific validity and clinical utility. Additionally, all participants in this study were cognitively normal and fully aware older adults, meaning that our findings do not extend to older patients with cognitive impairments. Despite these limitations, the results affirm the reliability and validity of the Physical Resilience Scale (PRS) in a Chinese context.

Considering the increasing recognition of resilience as a crucial factor in successful aging, it is both useful and necessary to translate and culturally adapt the PRS for community-dwelling older adults within the Chinese cultural milieu. A reliable and valid measure of physical resilience will enable researchers to focus on this aspect in older populations, thereby promoting healthy aging. The PRS can be regarded as a valuable tool for assessing resilience among older adults. Future research should concentrate on developing and evaluating specific interventions aimed at enhancing physical resilience, thereby assisting older adults who face acute events that typically impact physical abilities and performance.

Conclusion

In summary, this study demonstrates the reliability and validity of the Physical Resilience Scale (PRS) as a novel questionnaire for assessing recovery following challenging physical events in older adults. The results indicate that the PRS is a reliable and valid tool for use with older adults, featuring items that are easy to understand and a format that is both convenient and efficient, making it suitable for the cultural context of older adults in China. The questionnaire can effectively assess the level of physical resilience in older adults during recovery from significant physical stressors. Utilizing the PRS to measure physical resilience helps in identifying protective factors and developing intervention strategies. The increased incorporation of these measures during point-of-care visits would be a valuable resource for both research and healthcare communities. Such efforts could significantly benefit healthcare professionals, as timely and effective assessment of physical resilience can inform the selection of appropriate and timely treatments, optimize rehabilitation strategies, and aid in the development of robust transitional care plans for frail older adults.

Supplementary Information

Supplementary Material 1.

Abbreviations

PRS Physical Resilience Scale

DIF Differential item functioning

WHO World Health Organization

PRIFOR Physical Resilience Instrument for Older Adults

I-CVI Item-Content Validity Index

S-CVI Scale-Content Validity Index

CTT Classical Test Theory

IRT Item Response Theory

PCA Principal component analysis

Infit MNSQ Information-weighted fit statistics mean square

Outfit MNSQ Outlier-sensitive fit statistics mean square

Acknowledgements

We thank the participants of the study.

Authors’ contributions

This manuscript is submitted in the name of all participating authors. All authors made significant contributions to the study design, data collection and interpretation, and drafting of the manuscript. TTL, CZ, and FZA participated in the design of the study. AHD wrote the main manuscript and LHK prepared figures. FZF is responsible for data collection, and HJZ revises the manuscript.All authors reviewed the manuscript. All authors have approved the final submitted version of this manuscript.

Funding

No Funding.

Availability of data and materials

The datasets used and analysed during the current study are available from the corresponding author on reasonable request.

Declarations

Ethics approval and consent to participate

Ethical approval for this study was obtained from the Research Ethics Committee of Jinzhou Medical University. The application number was JZMULL2023087, and all participants gave informed consent. This study was conducted in accordance with the guidelines and regulations of Jinzhou Medical University.

Consent for publication

Not applicable as no individual identifable information published in this manuscript.

Competing interests

The authors declare no competing interests.

Publisher’s note

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
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