Abstract
Background
Half of all physical disability, including activity of daily living (ADL) disability, among older adults occurs in the setting of hospitalization. This study examines whether appendicular lean mass (ALM) and grip strength, which are commonly included in various definitions of sarcopenia, are associated with the development of hospital-associated ADL disability in older adults in the Health ABC Study.
Methods
Individuals hospitalized during the first 5 years of follow-up (n = 1 724) were analyzed. ALM to body mass index (BMI) ratio (ALMBMI), by dual-energy x-ray absorptiometry (DXA), and grip strength, by hand-held dynamometery, were assessed annually. Development of new ADL disability was assessed at the time of the next annual assessment after hospitalization. Separate regression analyses modeled the association of prehospitalization ALMBMI or grip strength with death before the next scheduled annual assessment. Next, among those who survived to the next annual assessment, separate regression analyses modeled the association of ALMBMI or grip strength with development of ADL disability.
Results
Each standard deviation decrement in prehospitalization grip strength was associated with an adjusted 1.80 odds of new ADL disability at follow-up (95% CI: 1.18, 2.74). Low, compared with not low, grip strength (per FNIH definition) was associated with an adjusted 2.36 odds of ADL disability at follow-up (95% CI: 1.12, 4.97). ALM measures were not associated with the development of hospital-associated ADL disability. ALM and grip strength measures were not associated with death.
Conclusions
Prehospitalization lower grip strength may be an important risk factor for ADL disability among older adult survivors of hospitalization.
Keywords: Activities of daily living, Hospital-associated disability, Lean mass, Grip strength, Sarcopenia
Inability to perform basic activities of daily living (ADLs) is a primary barrier to older adults’ ability to live independently and becomes increasingly common with advancing age (1–4). Remarkably, half of all physical disability among older adults arises in the setting of hospitalization (4,5), and at least 30% of all older adults hospitalized for an acute medical condition develop a new ADL disability by the time of hospital discharge (6). ADL disability that arises following an acute hospitalization is often referred to as hospital-associated ADL disability. As the population ages, hospital-associated ADL disability and its contribution to overall ADL disability among older adults is an increasingly urgent public health concern. However, understanding of the pathogenesis of hospital-associated ADL disability remains limited, and there are few known modifiable risk factors. Prehospitalization, modifiable risk factors may include depressive symptoms, cognitive function, and social support (7–9). Identification of important and modifiable risk factors for hospital-associated ADL disability would facilitate the development of novel interventions to prevent this major source of disability for older adults where currently few such interventions exist.
Sarcopenia, or aging-related declines in muscle mass and strength, is a key risk factor for the development of physical disability in older adults. Although there are no universally accepted criteria to identify sarcopenia, appendicular lean mass (ALM) measured by dual-energy x-ray absorptiometry (DXA), as a proxy for appendicular muscle mass, and grip strength measured by handheld dynamometery, are commonly included in various proposed definitions of sarcopenia (10–12) and used in studies of older adults (13–16). Grip strength, in particular, is strongly associated with the development of physical disability, such as mobility impairment, over time in older adults (15,17). Sarcopenia, which reflects an older adult’s vulnerability to becoming disabled after a precipitating event (18), is likely strongly associated with development of disability after an acute hospitalization. Thus, lower ALM and grip strength are likely to be associated with increased risk of hospital-associated ADL disability.
The aim of the present study was to evaluate whether ALM and grip strength, assessed using standard definitions, are important risk factors for the development of hospital-associated ADL disability among older adults who survived an acute hospitalization.
Method
Participants
Participants in the present analysis were participants in the Health Aging and Body Composition Study (Health ABC). Health ABC was a longitudinal cohort study focused on changes in body composition and physical function in older adults, initiated in 1997, that included 3 075 White and Black men and women aged 70–79 years and who were relatively free of physical disability at enrollment (19). Health ABC participants underwent annual assessment of ALM, grip strength, and ADL function during the first several years of follow-up. Individuals who were hospitalized during the first 5 years of follow-up in Health ABC were eligible for inclusion in the present study. The current analysis focuses on individuals’ first hospitalization (index hospitalization) during the follow-up period. Hospitalization was assessed by self-report every 6 months following a standardize protocol in Health ABC (14). For each reported hospitalization, medical records were collected centrally, and relevant clinical data were confirmed by local review. Health ABC participants who were never hospitalized (n = 383) were not eligible for the present study. In addition, individuals were excluded who were unable to perform independently 2 or more ADL activities prior to the index hospitalization (n = 2); who were missing ADL outcome data but who did not die within 1 year of last ADL assessment (n = 692); or who were missing ALM data (n = 26), grip strength data (n = 72), or both (n = 176) within 2 years before the index hospitalization. The final sample for the present study was comprised of 1 724 individuals (Supplementary Figure 1).
Measures
The primary predictors for the present study are ALM to body mass index (BMI) ratio (ALMBMI) and grip strength measured at the annual assessment most closely preceding the index hospitalization. ALM was determined from total body scans using fan-beam DXA (Hologic QDR 4500A; Hologic, Bedford, MA). ALMBMI was defined as the sum of lean mass in the arms and legs divided by BMI. Low ALMBMI was defined as <0.789 for men and <0.512 for women (17). Grip strength (kg) of the dominant hand was measured by hand-held dynamometer (Jamar) in 2 separate trials, and the maximum strength value was analyzed. Low grip strength was defined as <26 kg for men and <16 kg for women (20). This definition grip strength, which is not adjusted for BMI, was chosen to facilitate comparison with prior studies (15) and to adhere to the definitions put forth by the European Working Group on Sarcopenia in Older People (11).
The primary outcomes for the present study were development of new ADL disability, compared with prehospitalization, or death before the next scheduled annual assessment following the index hospitalization. New ADL disability was defined as newly being unable or needing help performing at least one of the following: bathing, dressing, or transferring in and out of chairs (21). These were the only 3 ADL tasks regularly assessed in the Health ABC Study. ADL disability was assessed by self-report, or proxy-report if needed. For each ADL task, participants were first asked if they, “have any difficulty” performing the task. If yes, participants were then asked, (i) “how much difficulty” (a little, some, a lot, or unable to perform) and (ii) “do you usually receive help from another person” when performing the task. The use of an assistive device such as a walker or cane was not considered as being disabled.
Sociodemographic characteristics (age, race), medical comorbidities (history of falls, diabetes, cancer, arthritis, pulmonary disease, cardiac disease, stroke, depression), current smoking status, BMI, modified Mini-Mental Status Examination (MMMSE) score, and physical activity (self-report of walking activity per week) were assessed following a standardized protocol at the time of enrollment in Health ABC (19,22,23).
Statistical Analysis
We used a logistic regression approach that conditions on survival to the next scheduled annual assessment to analyze the relationships of prehospitalization ALMBMI and grip strength with new ADL disability or death. In Health ABC, ADL disability status was assessed annually. Therefore, among our sample of hospitalized individuals, the development of new ADL disability status after the index hospitalization could not be ascertained in those who died prior to the next annual assessment. To address this limitation, separate logistic regression models first assessed the association of (i) ALMBMI or (ii) grip strength measures prior to hospitalization with the risk of death before the next scheduled annual assessment after hospitalization with and without adjusting for the covariates below. Then, only among those individuals who survived to the next annual assessment after the index hospitalization, separate logistic regression models assessed the association of (i) ALMBMI or (ii) grip strength measures prior to hospitalization with the risk of new ADL disability at the next annual assessment with and without adjusting for covariates. We also chose this analytic approach to better address the overarching clinically oriented goal of identifying risk factors for ADL disability among older adults recovering from a hospitalization. All multivariable models were adjusted for age, race, study site, MMMSE score, physical activity, smoking status, history of medical comorbidities, number of days from index hospital discharge to outcome (new ADL disability or death) assessment, number of days from prehospitalization ALMBMI or grip strength assessment to start of index hospitalization, index hospitalization length of stay in days, and number of hospitalizations within 356 days of the index hospitalization. Grip strength models were also adjusted for BMI. In preplanned secondary analyses, (i) the above models were stratified by sex and (ii) sarcopenia status was categorized as neither low grip strength nor low ALMBMI, versus low grip strength or low ALMBMI, versus low grip strength and low ALMBMI.
Results
Participant and Index Hospitalization Characteristics
Characteristics for the 1 724 participants in the present study are depicted in Table 1. Among all participants, 47% were female, 42% were of Black race, and the most common prevalent medical comorbidities were arthritis (59%), heart disease (29%), nonskin cancer (23%), and falls (22%). The mean number of days from assessment of ALMBMI and grip strength to index hospitalization admission was 305. Seventeen percent of participants met the definition of low ALMBMI and 10% of low grip strength prior to hospitalization. Eight participants (0.5%) were disabled in 1 ADL task prior to the index hospitalization. Table 1 also depicts index hospitalization characteristics. Among all participants, the mean length of stay was approximately 6 days, 11% of hospitalizations involved admission to the intensive care unit, and 97% of individuals were alive at the time of discharge from the index hospitalization. The most common reasons for index hospitalization were angina/myocardial infarction (13%), conditions of the circulatory system (11%), and conditions of the gastrointestinal system (11%). The mean number of total hospitalizations, including the index hospitalization, within 365 days of admission for the index hospitalization was 1.5.
Table 1.
Participant and Index Hospitalization Characteristics*
| Men n = 916 (53%) | Women n = 808 (47%) | Total n = 1 724 | |
|---|---|---|---|
| Age | 73.9 ± 2.9 | 73.6 ± 2.9 | 73.8 ± 2.9 |
| Black race, n (%) | 334 (36) | 389 (48) | 723 (42) |
| Memphis HABC study site, n (%) | 467 (51) | 367 (45) | 834 (48) |
| Pittsburgh HABC study site, n (%) | 449 (49) | 441 (55) | 890 (52) |
| MMMSE | 89.3 ± 8.9 | 90.3 ± 7.8 | 89.8 ± 8.4 |
| Smoking status, n (%) | |||
| Never | 259 (28) | 421 (52) | 680 (39) |
| Former | 554 (60) | 283 (35) | 837 (49) |
| Current | 103 (11) | 104 (13) | 207 (12) |
| Walking activity (kcal/kg/wk) | 9.7 ± 23.0 | 5.8 ± 13.9 | 7.9 ± 19.4 |
| BMI | 27.1 ± 3.9 | 27.9 ± 5.4 | 27.4 ± 4.7 |
| Prevalent health conditions, n (%) | |||
| Nonskin cancer | 248 (27) | 143 (18) | 391 (23) |
| Lung disease | 125 (14) | 120 (15) | 245 (14) |
| Heart disease | 313 (34) | 190 (24) | 503 (29) |
| Stroke | 70 (8) | 78 (10) | 148 (9) |
| Diabetes mellitus | 169 (18) | 128 (16) | 297 (17) |
| Falls | 173 (19) | 204 (25) | 377 (22) |
| Arthritis | 472 (52) | 538 (67) | 1010 (59) |
| Depression | 67 (7) | 96 (12) | 163 (9) |
| ALMBMI | 0.88 ± 0.11 | 0.60 ± 0.09 | 0.75 ± 0.17 |
| Low ALMBMI†, n (%) | 189 (21) | 112 (14) | 301 (17) |
| Grip strength, kg | 35.8 ± 7.7 | 21.5 ± 5.5 | 29.1 ± 9.8 |
| Low grip strength†, n (%) | 77 (8.4) | 103 (13) | 180 (10) |
| ADL disability, n (%) | 6 (0.7) | 2 (0.3) | 8 (0.5) |
| Days from ALMBMI/grip strength measurement to index hospitalization | 300 ± 251 | 310 ± 206 | 305 ± 231 |
| Days from index hospitalization to ADL assessment | 180 ± 123 | 178 ± 117 | 179 ± 120 |
| Hospital length of stay | 6.0 ± 7.0 | 5.5 ± 6.8 | 5.8 ± 6.9 |
| ICU admission (y/n), n (%) | 125 (14) | 73 (9) | 198 (11) |
| Alive at hospital discharge (y/n), n (%) | 880 (96) | 790 (98) | 1670 (97) |
| Primary discharge diagnosis category, n (%) | |||
| Angina/myocardial infarction | 140 (15) | 77 (10) | 217 (13) |
| Circulatory disease | 108 (12) | 77 (10) | 185 (11) |
| Gastrointestinal conditions | 88 (10) | 96 (12) | 184 (11) |
| Cancer | 108 (12) | 65 (8) | 173 (10) |
| Musculoskeletal conditions | 78 (9) | 100 (12) | 178 (10) |
| Other | 80 (9) | 83 (10) | 163 (9) |
| Cerebrovascular disease | 62 (7) | 60 (7) | 122 (7) |
| Trauma/Injury | 40 (4) | 64 (8) | 104 (6) |
| Genitourinary conditions | 52 (6) | 38 (5) | 90 (5) |
| Pneumonia | 35 (4) | 35 (4) | 70 (4) |
| COPD/asthma | 23 (3) | 25 (3) | 48 (3) |
| Congestive heart failure | 29 (3) | 28 (3) | 57 (3) |
| Endocrine conditions | 17 (2) | 20 (2) | 37 (2) |
| Neurologic | 18 (2) | 18 (2) | 36 (2) |
| Infection | 10 (1) | 2 (0.3) | 12 (1) |
| Pulmonary | 16 (2) | 7 (1) | 23 (1) |
| Dermatologic | 8 (1) | 9 (1) | 17 (1) |
| Dementia | 3 (<1) | 2 (<1) | 5 (<1) |
| Hematologic | 1 (<1) | 2 (<1) | 3 (<1) |
| Number of hospitalizations within 365 d of index hospitalization (including index) | 1.5 ± 0.9 | 1.5 ± 1.0 | 1.5 ± 0.9 |
| Total days hospitalized within 365 d of index hospitalization (including index) | 9.5 ± 11.1 | 8.7 ± 11.3 | 9.1 ± 11.2 |
Notes: ADL = activities of daily living; ALMBMI = appendicular lean mass to BMI ratio; BMI = body mass index; COPD = chronic obstructive pulmonary disease; MMMSE = modified mini-mental state examination.
*Values reported as mean ± SD unless otherwise noted.
†Low ALMBMI: men <0.789, women <0.512; low grip strength men <26 kg, women <16 kg (15).
Death and Incident ADL Disability
Table 2 depicts the numbers of participants who died and, among survivors, who developed new ADL disability at the time of the next annual assessment. One hundred and seventy-six participants (10%; 12% of men and 8% of women) died before time of the next scheduled annual assessment. Among participants who survived to the next annual assessment following the index hospitalization, 4% (3% of men and 5% of women) reported a new ADL disability. Overall, the most common newly disabled ADL tasks was bathing (2%).
Table 2.
Number and Percentage of Hospitalized Older Adults Who Died and, Among Survivors, Who Developed New Activity of Daily Living Disability at the Next Annual Health ABC Assessment
| Men n = 916 (53%) | Women n = 808 (47%) | Total n = 1 724 | |
|---|---|---|---|
| Death | 110 (12.0%) | 66 (8.2%) | 176 (10.2%) |
| ADL disability* | |||
| Any ADL | 25 (2.7%) | 38 (4.7%) | 63 (4.1%) |
| Transferring | 7 (0.8%) | 19 (2.4%) | 26 (1.5%) |
| Bathing | 10 (1.1%) | 29 (3.6%) | 39 (2.3%) |
| Dressing | 15 (1.6%) | 18 (2.2%) | 33 (1.9%) |
Notes: ADL = activity of daily living.
*ADL disability defined as newly being unable or needing help to bathe, dress, or transfer. Patients may have disability with more than one ADL.
Primary Results: Associations of ALMBMI and Grip Strength With ADL Disability or Death
In adjusted models, prehospitalization grip strength (as continuous measure or a categorical measure) was statistically significantly associated with an increased risk of new ADL disability among survivors at the next annual assessment (Table 3). Each standard deviation decrement in prehospitalization grip strength was associated with 1.83 times higher likelihood (95% CI [1.19, 2.81]) of new ADL disability when controlling for effects of covariates. The presence of prehospitalization low grip strength (vs not low) was associated with 2.49 times higher likelihood (95% CI [1.17, 5.29]) of new ADL disability when controlling for effects of covariates. Neither prehospitalization ALMBMI nor low ALMBMI were statistically significantly associated with new ADL disability among survivors at the next annual assessment in adjusted models.
Table 3.
Odds ratios and 95% Confidence Intervals for the Association of Prehospitalization Sarcopenia Measures With Death or, Among Survivors, With New Activity of Daily Living Disability at Next Annual Assessment Among Hospitalized Older Adults in the Health ABC Study
| Death | ADL Disability* | |||||
|---|---|---|---|---|---|---|
| n | Unadjusted | Adjusted† | n | Unadjusted | Adjusted† | |
| ALMBMI‡ | 1 724 | 0.81 (0.69, 0.94) | 0.85 (0.61, 1.17) | 1 548 | 1.32 (1.01, 1.73) | 1.27 (0.78, 2.08) |
| Low ALMBMI§ | 1 724 | 0.93 (0.61, 1.41) | 0.83 (0.49, 1.40) | 1 548 | 0.99 (0.51, 1.93) | 0.92 (0.44, 1.92) |
| Grip strength‡ | 1 724 | 0.95 (0.82, 1.11) | 1.20 (0.91, 1.60) | 1 548 | 1.59 (1.20, 2.10) | 1.83 (1.19, 2.81) |
| Low grip strength§ | 1 724 | 1.39 (0.80, 2.41) | 1.29 (0.65, 2.57) | 1 548 | 2.79 (1.38, 5.66) | 2.49 (1.17, 5.29) |
Notes: ADL = activity of daily living; ALMBMI = appendicular lean mass to BMI ratio; BMI = body mass index. Bold font denotes p < .05.
*ADL disability defined as newly being unable or needing help to bathe, dress, or transfer.
†Adjusted for age, sex, race, modified mini-mental status examination score, study site, physical activity (kcal/kg/wk of walking), smoking status, history of falls, history of diabetes, history of cancer, history of arthritis, history of pulmonary disease, history of cardiac disease, history of stroke, history of depression, number of days from sarcopenia measurement to index hospitalization admission, number of days from hospital discharge to outcome assessment, index hospitalization length of stay in days, and number of hospitalizations within 365 d of index hospitalization (including index hospitalization). Grip strength models are also adjusted for BMI.
‡Odds ratios are expressed per standard deviation decrement of the sarcopenia measure.
§Low ALMBMI: men <0.789, women <0.512; low grip strength men <26 kg, women <16 kg (15).
In adjusted models, none of the measures of ALMBMI or grip strength were statistically significantly associated with death. The association between prehospitalization grip strength, as a continuous measure, and death approached but did not achieve statistical significance in the adjusted model (adjusted odds ratio 1.20; 95% CI [0.91, 1.60]).
Secondary Results: Associations Stratified by Sex
In adjusted models stratified by sex, the overall patterns of the associations of ALMBMI and grip strength measures with death and ADL disability were largely unchanged (Supplementary Tables 1 and 2). The point estimates of the associations between prehospitalization grip strength (continuous measure) or low grip strength (categorical measure) with ADL disability among survivors at the next annual assessment were similar in magnitude and direction in sex-stratified analyses compared with non-sex-stratified analyses. The p-values of the interaction terms between sarcopenia measures and ADL or death outcomes were all greater than .05 (data not shown).
Secondary Results: Sarcopenia Status
The presence of both low grip strength and low ALMBMI, compared with neither low grip strength nor low ALMBMI, was statistically significantly associated with development of new ADL disability among survivors at the next annual assessment such that the adjusted odds ratio for ADL disability was 3.53 (95% CI 1.10, 11.3; Supplementary Table 3).
Discussion
Among older adult survivors of acute hospitalization, prehospitalization grip strength (as a continuous measure) was inversely associated with the risk of new ADL disability at follow-up such that for each standard deviation decrement in prehospitalization grip strength the odds of new ADL disability at follow-up nearly doubled. Similarly, the presence of low grip strength (as a categorical measure), according to the Foundation of the National Institutes of Health Sarcopenia Project definition of clinically relevant low grip strength, prior to hospitalization was associated with a more than doubled odds of new ADL disability at follow-up. The association between prehospitalization grip strength measures and development of new ADL disability after hospitalization persisted after adjustment for demographics, comorbidities, and physical activity, suggesting that grip strength adds to these traditional risk factors. In contrast, we did not observe an association between prehospitalization measures of lean mass and the development of new ADL disability at follow-up. These findings suggest that lower prehospitalization grip strength may be an important risk factor for hospital-associated ADL disability among older adults. Lower grip strength is a known risk factor for incident long-term physical disability, including ADL disability, among older adults, but to the best of our knowledge, these are among the first reports to suggest that grip strength may also be an important risk factor for hospital-associated ADL disability.
Our observation that lower prehospitalization grip strength is associated with increased risk of developing ADL disability after hospitalization among older adults may have implications for advancing understanding of the pathogenesis of hospital-associated ADL disability in older adults and for developing new strategies to improve functional outcomes of hospitalization in these patients. Grip strength is associated with muscle strength in other parts of the body (24) and is often included in assessments of physical frailty in older adults (18,25–27). Our observation that grip strength is associated with the risk of ADL disability after hospitalization suggests that physical frailty, and, in particular, a lower muscle strength, may contribute to the pathogenesis of hospital-associated ADL disability in older adults. In contrast to other commonly included components of physical frailty, such as comorbidities, weight loss, or fatigue, muscle strength may be a more readily modifiable risk factor for hospital-associated ADL disability. Thus, future studies should examine whether interventions to improve physical frailty, and specifically muscle strength, reduce the risk of hospital-associated ADL disability in older adults. For example, prior studies have demonstrated that strength training interventions applied during an acute hospitalization may improve posthospitalization physical function outcomes among older adults. Thus, future studies should evaluate whether similar strength training interventions for hospitalized older adults with sarcopenia could be particularly effective at preventing hospital-associated ADL disability (28,29). In addition, grip strength may be a useful tool for identifying older adults most at risk for hospital-associated ADL disability and/or those most likely to respond to interventions to prevent this type of disability. Dynamometer-based assessment of grip strength is practical and reliable, and thus grip strength may be useful in both the clinical and research settings to identify at-risk individuals.
In contrast to prehospitalization grip strength, we did not observe a similar relationship between prehospitalization ALMBMI and hospital-associated ADL disability among our cohort of older adults. There are various possible explanations for this observed lack of an association between ALMBMI and hospital-associated disability. First, differences in lean mass (as a proxy for muscle mass) may not significantly contribute to an older adults’ risk of ADL disability after hospitalization. Indeed, lean mass is not as consistently related to physical impairment outcomes, such as mobility impairment and functional decline, as is muscle strength. Alternatively, the lack of a significant association between ALMBMI and hospital-associated ADL disability could reflect limitations of DXA-based measures of lean mass. Lean mass measured by DXA includes not only muscle, but also water, and all other nonfat and nonbone tissue, and thus it is an approximation of skeletal muscle mass. Whether inconsistent relationships between DXA-based measures of lean mass and physical function outcomes in older adults could be the result of methodologic limitations of DXA have been reviewed elsewhere (30,31). Nevertheless, DXA-based measures of lean mass have many advantages and are included in the European Working Group on Sarcopenia in Older People’s definition of sarcopenia (11). ALMBMI is also a commonly used measure in studies of body composition and functional outcomes in older adults. Thus, use of this measure in the present study allows comparison to prior studies. Future studies, including those using alternative methods of directly assessing skeletal muscle mass in older adults, will need to further examine relationships between muscle mass and hospital-associated ADL disability in older adults.
Among all individuals, there was a suggestion of an association between lower prehospitalization grip strength (as a continuous measure) and death at follow-up (adjusted odds ratio 1.29, 95% CI [0.99, 1.69]), but this trend did not achieve statistical significance. Therefore, although grip strength is a known risk factor for overall mortality in older adults (15) and may also be a risk factor for hospital-associated ADL disability as observed in the present study, we did not find grip strength to be a statistically significant risk factor for death among hospitalized older adults. Inadequate power could have contributed to this failure to detect a statistically significant effect. Future studies will need to further examine any potential relationships between prehospitalization, grip strength, and risk of death in hospitalized older adults.
In prespecified secondary analyses, we did not observe significant interactions between sex and the associations of ALMBMI or grip strength with hospital-associated ADL disability. Thus, although relationships between body composition and long-term adverse functional outcomes, such as mobility impairment or death, may differ by sex (19,32), we did not observe similar trends among hospitalized older adults in the Health ABC Study. The relationships of lean mass or grip strength with hospital-associated ADL disability may not differ by sex. It is also possible that despite a relatively large sample size, our study remained inadequately power to detect sex-specific interactions.
The current study has certain limitations. First, the Health ABC study was not designed with the intent of examining functional outcomes of hospitalization. Therefore, lean mass, grip strength, and hospital-associated ADL disability were not assessed at consistent time points before and after hospitalization, respectively. Future prospective cohort studies of hospitalized older adults, in which prehospitalization muscle mass and strength and posthospitalization ADL function are systematically assessed, are needed. Second, we chose to adopt an analytic approach that conditions on survival until the next annual follow-up after hospitalization in order to focus on understanding the development of ADL disability among older adult survivors of hospitalization. However, due to this approach, interpretation of our observations should be limited to older adults who survive hospitalization. Moreover, how these trends observed among hospitalized older adults compare with trends among nonhospitalized older adults could not be examined, as the relatively small sample size of nonhospitalized older adults in the present study did not permit these comparisons. Third, lack of information on other ADL tasks, such as eating, toileting, and ambulation (which were not regularly assessed in the Health ABC Study), is a potential limitation. Finally, the Health ABC study included only White and Black participants who initially were not disabled, and so the observed trends may or may generalize to other populations of older adults. The study also has important strengths. It includes a relatively large sample of hospitalized older adults in whom body composition and ADL functional status were systematically and longitudinally assessed. The study also used measures of muscle mass (ALMBMI by DXA) and muscle strength (grip strength) that are well-established in geriatrics clinical outcomes research.
In conclusion, weaker-hospitalization grip strength was significantly associated with the development of new ADL disability among older adult survivors of hospitalization. Thus, weaker grip strength may be an important risk factor for hospital-associated ADL disability among these patients. Future studies, including prospective cohort studies of hospitalized older adults in which grip strength and ADL disability are systematically assessed around the time of hospitalization, should further examine the potential contribution of weaker grip strength to the development of hospital-associated ADL disability in these patients.
Funding
This research was supported by National Institute of Aging (NIA) grants K23AG058756 and R03AG063168 to Dr. Andrews. In addition, this research was supported by NIA Contracts N01-AG-6-2101; N01-AG-6-2103; N01-AG-6-2106; NIA grant R01-AG028050; and National Institute of Nursing Research grant R01-NR012459. Finally, this research was funded in part by the Intramural Research Program of the National Institute on Aging.
Conflict of Interest
None declared.
Supplementary Material
Author Contributions
All authors were involved in study conception and design, drafting the article or revising it critically for important intellectual contact, and in data analysis and interpretation. All authors approved the final version to be published. J.S.A. and L.S.G. contributed to the acquisition of data.
Contributor Information
James S Andrews, Department of Medicine, University of Washington, Seattle, Washington, USA.
Laura S Gold, Department of Radiology, University of Washington, Seattle, Washington, USA.
May J Reed, Department of Medicine, University of Washington, Seattle, Washington, USA.
Jose M Garcia, Department of Medicine, University of Washington, Seattle, Washington, USA; GRECC, VA Puget Sound Health Care System, Seattle, Washington, USA.
Robyn L McClelland, Department of Biostatistics, University of Washington, Seattle, Washington, USA.
Annette L Fitzpatrick, Departments Family Medicine, Epidemiology, and Global Health, University of Washington, Seattle, Washington, USA.
Catherine L Hough, Department of Medicine, Oregon Health and Science University, Portland, Oregon, USA.
Peggy M Cawthon, California Pacific Medical Center Research Institute, University of California San Francisco, San Francisco, California, USA.
Ken E Covinsky, Department of Medicine, University of California San Francisco, San Francisco, California, USA.
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