Abstract
Objective:
Develop and validate a modified Frailty Phenotype measure for older Mexican Americans participating in the Hispanic Established Populations for the Epidemiological Study of the Elderly (H-EPESE) and related studies.
Design:
Expert-based panel evaluation of content validity, cross-sectional analysis of construct validity and longitudinal analysis of criterion validity for a modified version of the Frailty Phenotype measure.
Setting:
Five southwestern states.
Participants:
1,833 community-dwelling Mexican Americans aged ≥67 years.
Measurements:
Frailty was assessed using the Frailty Phenotype measure (weight loss, weakness, exhaustion, slowness and low physical activity) and a modified Frailty Phenotype measure (replacing ‘low physical activity’ with ‘limitations in walking half a mile’). Each individual was classified as non-frail, pre-frail or frail based on both frailty measures (original vs. modified). Expert panel consensus was used to examine content validity. Spearman correlation, kappa, weighted kappa and bootstrapping kappa examined construct validity (n=1,833). Generalized linear mixed models, odds ratios, Cox proportional regression models, hazard ratios and C-statistics were used to analyze criterion validity (n=1,446) across four outcomes: hospitalization, physician visits, disability and mortality from Wave 3 (1998/99) through Wave 8 (2012/13).
Results:
The original and modified Frailty Phenotype measures had a strong correlation (r=0.89, p<.000) and agreement (κ=0.84, 95%CI=0.81–0.86; weighted κ=0.86, 95%CI=0.84–0.88; bootstrap κ=0.84, 95%CI=0.81–0.86; bootstrap weighted κ=0.86, 95%CI=0.84–0.88 with 1,000 bootstrapping samples). Four outcome models showed similar risk predictions for both frailty measures, with the exception of physician visits for frail participants.
Conclusion:
‘Limitations in walking half a mile’ can be used as a substitute criterion for ‘low physical activity’ in assessing frailty. The modified Frailty Phenotype measure was comparable to the original Frailty Phenotype measure in H-EPESE participants over time. Our results indicate the modified Frailty Phenotype is a useful longitudinally frailty measure for community-dwelling older Mexican Americans.
Keywords: Frail Elderly, Mexican Americans, Minority Health
INTRODUCTION
Frailty is associated with diminished reserve capacity, leading to increased risks for falls, fractures, cognitive impairment, disability, institutionalization and mortality1-5. Despite its significant impact on health, the operational definition of frailty remains unsettled6-7. Comprehensive reviews have documented significant variation in the measurement of frailty8-10.
The most common approaches to measuring frailty are the Frailty Index using cumulative deficits11-12 and Frailty Phenotype using weight loss, weakness, exhaustion, slowness and low physical activity13. Often, researchers create their own frailty index (i.e., using different cumulative deficits) or modify the Frailty Phenotype components (i.e., revising the five criteria)10,14, to match study samples or available resource at the time the study was conducted.
This investigation focused on the five-criterion Frailty Phenotype measure. A 2015 systematic review found only 24 of 264 studies (9.1%)10 used all five criteria originally proposed by Fried and colleagues (2001)13. Low physical activity and weight loss were the most-frequently modified of the five criteria; only 12.8% of 264 reviewed studies used both criteria as originally proposed10,15.
Population-based longitudinal survey studies, such as The Hispanic Established Population of Epidemiological Study of the Elderly (H-EPESE), are not always able to collect all five frailty criteria originally proposed in the Frailty Phenotype measure. The low physical activity criterion was collected during only one of the nine waves of the H-EPESE. The purpose of our study was to validate the use of a walking measure to replace the original physical activity item used to assess the Frailty Phenotype.
METHODS
Participants
The H-EPESE is an ongoing study since 1993/94 designed to understand the natural history of aging in Mexican Americans age 65 and older living in the community16. Participants were selected from Texas, Colorado, New Mexico, Arizona and California. Nine waves of data have been collected over 23 years17. Detailed information regarding the H-EPESE including the data collection methods, the survey instruments, supporting files (e.g., codebooks, etc.) and the de-identified data are available in the National Archive of Computerized Data on Aging located at the University of Michigan18.
We included participants age ≥ 67 with complete frailty information at Wave 2 (1995/96) with at least two follow-ups from Wave 3 (1998/99) to Wave 8 (2012/13) (N=1,833). The validation subsample was non-disabled at Wave 2 (1995/96) and had complete data on covariates and outcome variables used in four outcome prediction models (n=1,446) (Supplement Figure S1).
Original Frailty Phenotype Measure
The original Frailty Phenotype13 includes measures of weight loss, weakness, exhaustion, slowness and low physical activity. Weight loss was defined as loss of weight >10 pounds within a year (score=1). Weakness was identified if unable to perform test or grip strength in the lowest 20%1 (score=1) after adjusting for sex and Body Mass Index (BMI, calculated by kg/m2). Exhaustion was measured with positive responses to questions from the Center for Epidemiologic Studies Depression Scale.19 The questions were: “everything I did was an effort” or “I could not get going” (score=1). Gait speed was measured by a timed 8-foot walk test. Participants unable to perform the test or in the bottom 20% (adjusted for height and sex) were identified as slow (score=1). Physical activity was measured by the Physical Activity Scale for the Elderly (PASE)20 with the lowest 20% (adjusted by sex) rated as low physical activity (score=1).
Modified Frailty Phenotype Measure
We used Wave 2 (1995/96) data to generate the modified Frailty Phenotype measure because the PASE data were collected only at Wave 2 (1995/96). Our expert panel chose the item: “can you walk half a mile without help?” to replace the ‘low physical activity’ criterion for the modified Frailty Phenotype measure. Participants were identified as having low physical activity (score=1) if they answered “No” to the question “can you walk half a mile without help?” The other four frailty components remained the same (Supplement Table S1). For each phenotype measure, participants were categorized as non-frail (0 criterion), pre-frail (1–2 criteria) or frail (3+ criteria), based on the five components.
Outcome Variables
We examined four outcomes: hospitalization, physician visits, disability and mortality. Each outcome was collected from Wave 3 (1998/99) to Wave 8 (2012/13) and coded as a dichotomous variable (yes/no) for each Wave. Hospitalization was identified if the respondent or proxy answered “Yes” to: “Did you experience an illness or injury that required staying overnight or longer in a hospital?” Physician visits were collected by asking: “How many times in the past 12 months, have you visited with a medical doctor?.” Physician visits were identified as “Yes” if they reported more than four visits (median at Wave 3) in the past year. Disability was defined as requiring assistance or being unable to perform one of the following: walking, bathing, grooming, dressing, eating, transferring from bed to chair and toileting21. Fifteen-year mortality (1998/99–2012/13) was determined using the date of death from the National Death Index and reports from relatives or proxies at each Wave.
Covariates
Covariates included time (identified by waves), sociodemographic variables (age, gender, marital status, education and Non-US born), BMI, cognitive impairment (defined by the Mini-Mental State Examination score <2122), current smoking status and comorbidity status (self-report of any of the following: arthritis, diabetes, hypertension, heart attack, stroke, cancer and hip fracture).
Content Validity
Content validity requires items adequately sample the overall universe of content being measured23,24. H-EPESE frailty experts discussed the appropriateness of using the replacement item (“can you walk half a mile without help?”) to indicate low physical activity for the H-EPESE sample. Experts also identified published literature using walking items as a physical frailty measure.10, 25, 26
Construct Validity
Construct validity refers to whether the new measure reflects the original construct23,24. We tested the construct (convergent) validity of the modified Frailty Phenotype measure with Spearman correlation of frailty status classification (frail, pre-frail and non-frail) and agreement using kappa, weighted kappa and bootstrapping kappa. Bootstrapping kappa generated estimates and confidence intervals based on 1,000 bootstrapping samples. We used McHugh’s27 cutoffs to determine the levels of kappa agreement (0.60–0.79, moderate; 0.80–0.90, strong; above 0.90, almost perfect).
Criterion Validity
Criterion validity is established when a new instrument classifies individuals similarly as the reference instrument23,24. We tested the criterion (predictive) validity for outcomes using the frailty classification generated by both measures. Generalized linear mixed modeling with PROC GLIMMIX procedure and Cox Proportional regression model were applied for binary outcomes. Odds ratios (OR) and hazard ratio (HR) were generated and no proportionality issue was found. C-statistics were used for model comparison28-29 (p<0.05 as significance level). Analyses were performed using SAS 9.4 (SAS Institute, Inc., Cary, NC).
RESULTS
The mean age was 75.6 years (SD=6.6) at Wave 2 (1995/96) (N=1,833). The majority were female (58.6%), married (54.0%), non US-born (56.0%), had 1–7 years of formal education (55.2%), BMI of 25–30 (39.6%), had no cognitive impairment (79.4%), no functional disability (94.3%), were non-smokers (88.2%), had hypertension (59.1%) and had physician visit(s) during the past year (85.9%) (Table 1).
Table 1.
Sample Characteristics at Wave 2 (1995/96) (N=1,833).
| Frailty Phenotype | Total | Original | Modified | ||||
|---|---|---|---|---|---|---|---|
| Frailty Status/ Variables |
N=1,833 | Non-Frail (n=902) |
Pre-Frail (n=800) |
Frail (n=131) |
Non-Frail (n=856) |
Pre-Frail (n=818) |
Frail (n=159) |
| Age, Number (%) | |||||||
| 65–74 years | 1,048 (57.2) | 592(65.6) | 419 (52.4) | 37 (28.2) | 569 (66.5) | 430 (52.6) | 49 (30.8) |
| 75-84 years | 642 (35.0) | 274 (30.4) | 310 (38.8) | 58 (44.3) | 256 (29.9) | 318 (38.9) | 68 (42.8) |
| 85+ years | 143 (7.8) | 36 (4.0) | 71 (8.9) | 36 (27.5) | 31 (3.6) | 70 (8.6) | 42 (26.4) |
| Age, Mean (SD) | 74.7(6.0) | 73.6 (5.2) | 75.2 (6.0) | 79.5 (7.4) | 73.4 (5.0) | 75.2 (6.1) | 79.3 (7.3) |
| Female | 1074 (58.6) | 530 (58.8) | 455 (56.9) | 89 (67.9) | 495 (57.8) | 473 (57.8) | 106 (66.7) |
| Education (years) | |||||||
| 0 | 292 (15.9) | 136 (15.1) | 123 (15.4) | 33 (25.2) | 127 (14.8) | 131 (16.0) | 34 (21.3) |
| 1-7 | 1101 (55.2) | 510 (56.5) | 517 (64.6) | 74 (56.4) | 481 (56.2) | 520 (63.6) | 100 (62.9) |
| ≥ 8 | 420 (22.8) | 249 (27.6) | 152 (19.0) | 19 (14.4) | 240 (28.0) | 159 (19.4) | 21 (13.1) |
| Married | 990 (54.0) | 493 (54.7) | 439 (54.9) | 58 (44.3) | 477 (55.7) | 438 (53.6) | 75 (47.2) |
| Non-US Born | 806 (56.0) | 394 (43.7) | 342 (42.8) | 70 (53.4) | 370 (43.2) | 359 (43.9) | 77 (48.4) |
| BMI, Mean (SD) | 28.0 (5.1) | 28.4 (5.0) | 27.8 (5.2) | 26.9 (5.4) | 28.3 (4.8) | 27.8 (5.3) | 27.4 (6.0) |
| Cognitively Impaired | 378 (20.6) | 138 (15.3) | 186 (23.3) | 54 (41.2) | 131 (15.3) | 188 (23.0) | 59 (37.1) |
| MMSE ≤ 21, N (%) | |||||||
| ADL Disabled, N (%) | 104 (5.7) | 4 (.44) | 48 (6.0) | 52 (39.6) | 1 (.1) | 42 (5.1) | 61 (38.4) |
| Smoking, N (%) | 216 (11.8) | 112 (12.4) | 93 (11.6) | 11 (8.4) | 109 (12.7) | 93 (11.4) | 14 (8.8) |
| Comorbidity | |||||||
| Mean (SD) | 1.5 (1.1) | 1.4 (1.0) | 1.6 (1.1) | 1.9 (1.3) | 1.4 (1.0) | 1.6 (1.1) | 2.1 (1.3) |
| Hospitalization | 238 (13.0) | 94 (10.4) | 120 (15.0) | 24 (18.3) | 89 (10.4) | 114 (13.9) | 35 (22.0) |
| Disability | 70 (3.8) | 3 (0.3) | 34 (4.3) | 33 (25.2) | 0 (0.0) | 30 (3.7) | 40 (25.2) |
| Physician Visits (≥4) (Yes) | 1333 (72.2) | 671 (74.4) | 586 (73.3) | 76 (58.0) | 641 (74.9) | 586 (71.6) | 106 (66.7) |
| Mortality | 1160 (63.3) | 581 (64.4) | 501 (62.6) | 70 (53.4) | 560 (65.4) | 510 (62.3) | 90 (56.6) |
BMI: Body Mass Index; MMSE: Mini-Mental State Examination; ADL: Activity of Daily Living; SD: Standard Deviation.
Content Validity
Rockwood et al. (2007)14 used “unable to walk or needs help to walk” to measure ‘low energy expenditure’ (comparable to ‘low physical activity’) in comparing measures of frailty in older adults in the Canadian Study of Health and Aging (CSHA), the Women’s Health and Aging Study (WHAS) and the Cardiovascular Health Study (CHS). Both the WHAS and CHS used ‘walking for exercise’ as one of the items to measure low physical activity. In the Survey of Health, Ageing, and Retirement in Europe (SHARE) and Romero-Ortuno et al.’s (2010)26 study, walking was also assessed as part of their modified physical activity criterion using the question: “how often do you engage in activities that require a low or moderate level of energy such as gardening, cleaning the car, or taking a walk?” Theou et al.’s systematic review10 also identified five articles using ability to walk to measure physical activity criterion. The expert panel discussed and agreed that “can you walk half a mile without help?” appeared to have good content validity.
Construct Validity
Participants were classified by the original versus modified criteria as non-frail (49.5% vs. 44.7%), pre-frail (43.7% vs. 44.7%) or frail (6.8% vs. 8.4%), respectively at Wave 2. We found a strong correlation (r=0.89, p<.0001) of frailty status classifications between the original and modified Frailty Phenotype measures.
Kappa, weighted kappa and bootstrapping kappa showed strong agreements (Table 2). The modified measure demonstrated good construct validity.
Table 2.
Original Sample and Bootstrapping Kappa Agreement Testing (Original vs. Modified Frailty Phenotype Measures) (N=1,833).
| Comparison on Local Mutual
Information |
|||||
|---|---|---|---|---|---|
| Original versus Modified |
Iagreement | Mutual Information |
Result (P value) |
Kappa (95% CI) |
Weighted Kappa (95% CI) |
| (Non-Frail, Pre-Frail, Frail) | 1.04 | 0.86 | Agreement (P < 0.001) |
0.84 (0.81, 0.86) |
0.86 (0.84, 0.88) |
| 0.86B (0.81, 0.91)B |
0.84B (0.81, 0.86) B |
0.86B (0.84, 0.88) B |
|||
Note: B = estimates and confidence intervals based on 1,000 bootstrapping samples.
Criterion Validity
Detailed ORs and 95%CI for each outcome were provided in Table 3. The results were similar when using the original and modified Frailty Phenotype measures in predictions of hospitalization, disability and physician visits. The modified Frailty Phenotype measure had higher odds in physician visits for frail individuals compared to the original measure (modified vs. original ORs for frail: 2.13 vs. 1.37).
Table 3.
Predictive Validity of Four Outcomes (Original vs. Modified Frailty Phenotype Measures) (N=1,446)
| Original | Modified | |||||
|---|---|---|---|---|---|---|
| OR | 95% CI | OR | 95% CI | |||
| Hospitalization | ||||||
| Pre-frail | 1.12 | 0.95 | 1.32 | 1.14 | 0.96 | 1.34 |
| Frail | 1.13 | 0.61 | 1.74 | 1.40 | 0.93 | 2.11 |
| AUC | 0.64 | 0.64 | ||||
| Disability* | ||||||
| Pre-frail | 1.51 | 1.20 | 1.90 | 1.61 | 1.28 | 2.02 |
| Frail | 3.29 | 1.68 | 6.45 | 3.34 | 1.91 | 5.84 |
| AUC | 0.89 | 0.90 | ||||
| Physician Visit^ | ||||||
| Pre-frail | 1.41 | 1.11 | 1.80 | 1.32 | 1.03 | 1.69 |
| Frail | 1.37 | 0.70 | 2.68 | 2.13 | 1.19 | 3.81 |
| AUC | 0.70 | 0.70 | ||||
| Mortality | ||||||
| HR | HR | |||||
| Pre-frail | 1.16 | 1.08 | 1.25 | 1.19 | 1.11 | 1.29 |
| Frail | 2.51 | 2.05 | 3.08 | 2.20 | 1.86 | 2.61 |
| AUC | 0.60 | 0.60 | ||||
OR: Odds Ratio; CI: Confidence Interval; AUC: Area under the curve; HR: Hazard Ratio;
Disability*: the respondent was considered as disable if he/she could not perform at least one (≥1) activity in the Katz’s Activities of Daily Living scale; Physician Visit^: yes/no (Yes: had more than four physician visits in the past year).
Using the modified Frailty Phenotype measure, pre-frail (HR=1.20, 95%CI=1.11–1.29) and frail (HR=2.20, 95%CI=1.86–2.61) participants had higher risk of 15-year mortality than the non-frail. The results were similar to those using the original Frailty Phenotype.
The Area Under the Curve (AUC) values were similar in all four outcomes for both measures (Table 3).
DISCUSSION
We developed a modified Frailty Phenotype measure using ‘can you walk half a mile without help?’ to substitute the physical activity criterion of the original Frailty Phenotype measure13. We found the modified measure demonstrated good content, construct and criterion validities. Our results support using the modified Frailty Phenotype measure to assess frailty status in older adults longitudinally.
The H-EPESE represents the most comprehensive and longest running examination of the natural history of aging among Mexican Americans in the U.S. Over twenty years of data have been collected and analyzed since 1993. The modified Frailty Phenotype measure can be applied to future studies using H-EPESE data to answer new research questions related to the aging process and health outcomes for older Mexican Americans. Currently, over 370 articles in peer-reviewed journals have been published from 1996 to 2018 using the H-EPESE data and the files in the National Archive had been downloaded over 8,300 times18. Our findings will expand future secondary analyses of new research questions relevant to a wide range of topics involving frailty in this minority population.
Multiple studies have replaced low physical activity criterion with other measures and ‘walking’ has been used as a replacement10,14,26. The European SHARE project showed good construct and predictive validity when using ‘walking’ to measure physical activity in predicting mortality among older adults from twelve European countries.26 Our study is the first we are aware of to examine the validity of self-reported walking to reflect overall physical activity in the context of physical frailty for older Mexican Americans. Our findings suggested the walking item we examined is a potential candidate to efficiently capturing low physical activity for older adult populations.
Our study had several limitations. The modified measure developed in our study was associated with higher odds of physician visits for frail participants than the original measure. This difference could be due to the restricted selection criteria applied in our outcome modeling. Although studies have shown that frail individuals tend to have higher risk of hospitalization or intensive care admission34, the associations between physician visits and frail status remains relatively unexplored. Future studies are recommended to explore this topic. In addition, our measure of frailty did not include a cognitive component. The original Frailty Phenotype and our modified Frailty Phenotype are measures of physical frailty. The role of cognition in the frailty process is important and needs continued investigation. Fried and colleagues13 also suggested a cognitive component should be included when measuring frailty.
Overall, the modified Frailty Phenotype measure demonstrated strong content validity, robust agreement and similar outcome predictions when compared to the original measure in community-dwelling older Mexican Americans. Our results provide support for the use of the ‘ability to walk a defined distance without help’ item as an indicator of physical activity in older Mexican Americans. We assume similar results will be found for older adults of other racial and ethnic groups. Additional research is necessary to determine the appropriateness of the modified Frailty Phenotype measure for other populations.
Supplementary Material
Supplement Figure S1. Cohort Selection Diagram
Supplement Table S1. Five Frailty Criteria Used in the Original and the Modified Frailty Phenotype Measures.
Acknowledgments
Sponsor’s Role
This study was supported by the National Institutes of Health, the National Institute on Aging (R01-AG10939) and the National Institute on Minority Health and Health Disparities (R01-MD010355). The funding agencies had not influence on the results or input in preparing the manuscript.
ABBREVIATIONS
- BMI
Body Mass Index
- CHS
Cardiovascular Health Study
- CSHA
Canadian Study of Health and Aging
- H-EPESE
Hispanic Established Populations for the Epidemiological Study of the Elderly
- HR
Hazards Ratios
- OR
Odds Ratio
- PASE
Physical Activity Scale for the Elderly
- WHAS
Women’s Health and Aging Study
Footnotes
Conflict of Interest
All authors declare that they had no conflicts of interest in any regard with respect to publishing this paper.
Handheld Dynamometer: Jaymar Hydraulic Dynamo-meter #5030J1; J.A. Preston Corp., Jackson, MI
Brief Descriptive Title for The Supplemental Material: The study cohort selection diagram and the comparison of the five frailty criteria used in the original and the modified frailty phenotype measures.
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Associated Data
This section collects any data citations, data availability statements, or supplementary materials included in this article.
Supplementary Materials
Supplement Figure S1. Cohort Selection Diagram
Supplement Table S1. Five Frailty Criteria Used in the Original and the Modified Frailty Phenotype Measures.