Abstract
Background
Evaluating asymmetries in muscle function could provide important insights for fall risk assessments. We sought to determine the associations of (i) handgrip strength (HGS) asymmetry and (ii) leg extension power (LEP) asymmetry on risk of incident recurrent falls and fractures in older men.
Method
There were 5 730 men with HGS asymmetry data and 5 347 men with LEP asymmetry data from the Osteoporotic Fractures in Men (MrOS) study. A handgrip dynamometer measured HGS and a Nottingham Power Rig ascertained LEP. Percent difference in maximal HGS between hands was calculated, and asymmetric HGS was defined as men in the highest quartile of dissimilarity for HGS between hands. The same approach was used to determine asymmetric LEP. Participants self-reported falls every 4 months after the baseline exam, and persons with ≥2 falls in the first year were considered recurrent fallers. Fractures and their dates of occurrence were self-reported and confirmed with radiographic reports.
Results
Older men in the highest HGS asymmetry quartile had a 1.20 (95% confidence interval [CI]: 1.01–1.43) relative risk for incident recurrent falls. Likewise, men in the highest HGS asymmetry quartile had a higher risk for incident fractures: 1.41 (CI: 1.02–1.96) for hip, 1.28 (CI: 1.04–1.58) for major osteoporotic, and 1.24 (CI: 1.06–1.45) for nonspine. There were no significant associations between LEP asymmetry and recurrent falls or fractures.
Conclusions
Asymmetric HGS could be a novel risk factor for falls and fractures that is more feasible to measure than LEP. Fall risk assessments should consider evaluating muscle function, including HGS asymmetry.
Keywords: Falls, Geriatric assessment, Muscle, Sarcopenia
Falls are a substantial public health problem in the United States such that over a quarter of older Americans sustain a fall each year, which signifies 29 million falls that result in 7 million injuries requiring medical attention (1). There are several risk factors linked to falls and many of them are modifiable (2). Federal public health initiatives for fall prevention, such as the Stopping Elderly Accidents, Deaths and Injuries (STEADI) (3), examine a variety of risk factors including physical performance (4), which is an objectively measured whole body movement related with mobility that involves many body organs and systems (5,6). Although low physical performance is associated with future falls and related fractures, physical performance examinations are not without limitations (5,7–9). Given that poor muscle function represents the onset of the disabling process and precedes declines in physical performance (5), assessing muscle function in fall risk assessments could provide a physical measure that not only overcomes the limitations of physical performance assessments, but also maintains feasibility for use in clinical and translational research settings.
Poor muscle function is a hallmark risk factor for falls, fractures, and subsequent age-related disability (10). Handgrip strength (HGS) and leg extension power (LEP) are widely used assessments of muscle function in research settings (5). While HGS and LEP uniquely assess muscle function for the upper and lower extremities, respectively, the highest performing measure of HGS and LEP, regardless of extremity dominance, is often included in analyses (11,12). The other measures of HGS and LEP not included are typically overlooked, although they may provide valuable insights into muscle function. For example, wide differences in HGS between hands, as characterized by HGS asymmetry, have been shown to be independently and longitudinally associated with functional disability (13), cognitive impairment (14), and early all-cause mortality in aging adults (15).
Evaluating how muscle strength and power asymmetries are associated with other age-related clinically relevant health outcomes, such as falls and fractures, may help us further understand the role of asymmetry in the intrinsic capacity framework and the disabling cascade (5,16,17). Such an understanding may guide the inclusion of muscle function measures in fall risk assessments and provide earlier opportunities for fall prevention interventions. This may, in turn, help to better predict falls, provide specificity for how physical measures are associated with falls, and extend independence and longevity in the rapidly growing older American population. We sought to determine the associations of (i) HGS asymmetry and (ii) LEP asymmetry on risk of incident recurrent falls and fractures in older men.
Methods
Participants
During the Osteoporotic Fractures in Men (MrOS) study baseline examination (March 2000 to April 2002), 5 994 community-dwelling men aged ≥65 years that were ambulatory and free from bilateral hip replacement were recruited to participate in the study at 6 different clinical centers across the United States: Birmingham, AL; Minneapolis, MN; Palo Alto, CA; the Monongahela Valley (near Pittsburgh), PA; Portland, OR; and San Diego, CA. A self-administered questionnaire, battery of clinical exams, and physical tests were completed. Protocols were standardized across sites and measures were completed during a single visit on the same day. The analytic sample consisted of men with data for HGS or LEP on each hand or leg, respectively (n = 5 938). All participants provided written informed consent, and study protocols were approved by the institutional review boards at all centers. More details regarding the MrOS study are available elsewhere (18,19).
Measures
Falls and fractures
After the baseline exam, participants completed and returned a mailed questionnaire regarding incident falls and fractures every 4 months; a response to at least one questionnaire was >99% (18). Men who reported falling were asked how many times they fell. Falls reported in the first year after the baseline visit were included in the analyses. Participants with ≥2 falls were classified as recurrent fallers. Fractures and their dates of occurrence were self-reported and confirmed centrally by radiographic reports. Fracture outcomes included: major osteoporotic (hip, wrist, proximal humerus, clinical spine), hip, nonspine, and clinical spine. Participants were followed for up to 10 years, or until death or loss to follow-up (8.7 ± 2.4 years).
Handgrip strength asymmetry
A Jamar handgrip dynamometer (Sammons Preston Rolyan, Bolingbrook, IL) measured HGS. The Jamar dynamometer has an excellent test–retest reliability for both hands (interclass correlations: 0.97 for the left hand; 0.98 for the right hand) in older adults (20). In brief, participants squeezed the dynamometer with maximal effort for 2 trials on each hand. The highest recorded HGS on each hand was included in the calculation for asymmetry. A percent difference in maximal HGS between each hand was calculated as: 100*(|Maximal left HGS − Maximal right HGS|)/(Overall maximal HGS). Asymmetric HGS was defined to include men in the highest quartile of dissimilarity for HGS measurements between the weaker and stronger hand (≥14.8% dissimilarity). Those with missing HGS asymmetry data were not included in the analyses (n = 208).
Leg extension power asymmetry
A Nottingham Power Rig (University of Nottingham, Nottingham, England) was used to measure LEP. The Nottingham Power Rig has demonstrated a 3.5% coefficient of variation regardless of leg during separate visits occurring 1 week apart in older men from the MrOS (21). More details about the LEP measure are described elsewhere (21). Briefly, each participant was positioned in an adjustable seat with their hip and knee angled at about 90° before pressing a single foot on a pedal until the leg was extended. A flywheel accelerated when participants pushed the pedal, thereby creating a measure of power (W). Each participant completed up to 9 trials on each leg. The coefficient of variation for maximal LEP on either leg was 11.2%. The highest recorded LEP on each leg was included in the calculation for asymmetry.
The percent difference in maximal LEP between each leg was calculated as: 100*(|Maximal left LEP − Maximal right LEP|)/(Overall maximal LEP). LEP asymmetry was also defined to include men in the highest quartile of dissimilarity for LEP measures between the weaker and stronger leg (≥13.5% dissimilarity). Those with missing LEP asymmetry data were not included in the analyses (n = 591).
Covariates
Participants self-reported their age, race, alcohol intake, and cigarette smoking status. Standing height was measured with a wall-mounted Harpenden stadiometer (Holtain, Crymych, UK) and body weight with an electronic scale. Body mass index (BMI) was calculated as body weight in kilograms divided by height in meters-squared (kg/m2). To determine benzodiazepine usage, participants were asked to bring current prescription medications (within the proceeding 30 days) with them to examinations. Medications were entered into an electronic database, and each medication was matched to its ingredients based on the Iowa Drug Information Service Drug Vocabulary (University of Iowa, Iowa City, IA) (22). Femoral neck bone mineral density was obtained from hip dual-energy x-ray absorptiometry scans (Hologic, Belford, MA). Cognitive functioning was assessed with the modified Mini-Mental State Examination (23). Scores ranged from 0 to 30 with higher scores representing greater cognitive functioning. The continuous scores for cognitive functioning were included in the analyses.
Physical activity participation was measured using the Physical Activity Scale for the Elderly (PASE) (24). Overall PASE scores ranged from 0 to 400, with higher scores suggesting greater physical activity participation. Continuous PASE scores were included in the analyses. Respondents were also asked if a health care provider had ever diagnosed them with selected medical conditions including heart failure, chronic obstructive pulmonary disease, diabetes mellitus, stroke, myocardial infarction, hypertension, Parkinson’s disease, cancer (excluding non-melanoma skin cancers), and osteoarthritis. The number of affirmative morbid diagnoses were summed and the continuous score (ranging from 0 to 9) was included in the analyses.
Statistical Analysis
All analyses were conducted with SAS 9.4 (SAS Institute Inc., Cary, NC). The descriptive characteristics were presented as mean ± SD for continuous variables and frequency (percentage) for categorical. To determine differences in the baseline descriptive characteristics by the LEP and HGS asymmetry groups, independent t tests (normally distributed continuous variables), Wilcoxon rank-sum tests (continuous variables with skewed distributions), and chi-squared tests for categorical variables were performed. A Spearman correlation analysis quantified the relationship between HGS and LEP asymmetry.
Separate negative binomial regression models analyzed the associations of (i) HGS asymmetry and (ii) LEP asymmetry on risk of incident recurrent falls. Individual proportional hazard regression models examined the association of (i) HGS asymmetry and (ii) LEP asymmetry on incident hip fractures, major osteoporotic fractures, nonspine fractures, and clinical spine fractures. The reference groups were individuals not in the highest quartile of asymmetry for each model. All models were first minimally adjusted for age and clinic site. The models were then fully adjusted for age, clinic site, race, alcohol intake, cigarette smoking status, BMI, cognitive functioning, physical activity participation, benzodiazepine use, multimorbidity score, and baseline HGS or LEP (for the appropriate predictor). For further precision in modeling, models with fracture outcomes were also adjusted for femoral neck bone mineral density. The results from the fully adjusted models were used for our principal findings.
As a supplementary analysis, both HGS and LEP asymmetry were included in a minimally and fully adjusted negative binomial regression model for the association on incident recurrent falls. Likewise, both HGS and LEP asymmetry were again included in minimally and fully adjusted proportional hazard regression models for the associations with incident hip fractures, major osteoporotic fractures, nonspine fractures, and clinical spine fractures. An alpha level of .05 was used for all analyses.
Results
The baseline descriptive characteristics of the participants are presented in Table 1. Of the 5 347 participants with data for LEP asymmetry, 1 337 (25.0%) were considered as having asymmetric LEP. Likewise, of the 5 730 with data for HGS asymmetry, 1 452 (25.3%) were classified as having asymmetric HGS. The men in our analytic cohort were aged 73.6 ± 5.9 years and had a BMI of 27.4 ± 3.8 kg/m2. Compared to men without LEP asymmetry, those with LEP asymmetry were older, had a higher BMI, and were living with a greater number of morbidities (p < .05). Similarly, relative to men without HGS asymmetry, persons with HGS asymmetry were also older and living with a greater number of morbidities (p < .05). The Spearman correlation coefficient revealed that HGS and LEP asymmetry were not related (r = .01; p = .34).
Table 1.
Baseline Descriptive Characteristics of the Participants
| Leg Extension Power | Handgrip Strength | ||||
|---|---|---|---|---|---|
| Overall | No Asymmetry | Asymmetry | No Asymmetry | Asymmetry | |
| (N = 5 938) | (n = 4 010) | (n = 1 337) | (n = 4 278) | (n = 1 452) | |
| Age (y) | 73.6 ± 5.9 | 73.2 ± 5.7 | 74.4 ± 6.1* | 73.4 ± 5.8 | 74.1 ± 6.0* |
| Non-White race, n (%) | 621 (10.5) | 441 (11.0) | 129 (9.6) | 444 (10.4) | 155 (10.7) |
| Smoking status, n (%) | |||||
| Never | 2 224 (37.5) | 1 506 (37.6) | 509 (38.1) | 1 619 (37.9) | 531 (36.6) |
| Past | 3 508 (59.1) | 2 359 (58.8) | 792 (59.2) | 2 507 (58.6) | 870 (59.9) |
| Current | 205 (3.5) | 144 (3.6) | 36 (2.7) | 151 (3.5) | 51 (3.5) |
| Body mass index (kg/m2) | 27.4 ± 3.8 | 27.2 ± 3.7 | 27.7 ± 3.8* | 27.3 ± 3.8 | 27.5 ± 4.0 |
| Comorbidities (range 0–9) | 1.3 ± 1.1 | 1.2 ± 1.1 | 1.4 ± 1.1* | 1.2 ± 1.1 | 1.3 ± 1.2* |
| Cognitive function score (range 0–100) | 93.3 ± 5.8 | 93.6 ± 5.7 | 92.9 ± 5.8* | 93.4 ± 5.8 | 93.2 ± 5.6 |
| Alcohol intake, n (%) | |||||
| None | 2 090 (35.2) | 1 352 (33.8) | 482 (36.1) | 1 492 (34.9) | 529 (36.5) |
| 1–13 drinks/wk | 3 149 (53.1) | 2 161 (54.0) | 706 (52.8) | 2 280 (53.4) | 760 (52.4) |
| 14+ drinks/wk | 691 (11.7) | 492 (12.3) | 148 (11.1) | 501 (11.7) | 160 (11.0) |
| Benzodiazepine usage, n (%) | 203 (3.6) | 136 (3.5) | 39 (3.0) | 135 (3.3) | 59 (4.2) |
| Femoral neck BMD (g/cm2) | 0.78 ± 0.13 | 0.78 ± 0.13 | 0.78 ± 0.13 | 0.79 ± 0.13 | 0.78 ± 0.13 |
| Maximum leg extension power (W) | 208.3 ± 63.1 | 211.5 ± 61.8 | 200.4 ± 65.6* | 210.8 ± 63.0 | 202.8 ± 63.5* |
| Maximum handgrip strength (kg) | 41.6 ± 8.5 | 42.4 ± 8.4 | 40.5 ± 8.6* | 41.7 ± 8.3 | 41.7 ± 8.8 |
| Overall follow-up from Visit 1 (y) | 8.6 ± 2.4 | 8.8 ± 2.3 | 8.5 ± 2.5* | 8.8 ± 2.4 | 8.6 ± 2.4 |
Notes: BMD = bone mineral density.
*p < .05.
Table 2 shows the results for the associations of HGS and LEP asymmetry on risk of incident recurrent falls. In the fully adjusted models, men in the highest HGS asymmetry quartile had a 1.20 (CI: 1.01–1.43) greater risk for recurrent falls. Although the magnitude of the association was similar to that between HGS asymmetry and incident recurrent falls, no statistically significant association existed between participants in the highest LEP asymmetry quartile and recurrent falls (relative risk: 1.19; CI: 0.99–1.43). Supplementary Table 1 provides the complete results from the fully adjusted models examining the associations of HGS and LEP asymmetry on the risk of incident recurrent falls.
Table 2.
Associations of Handgrip Strength and Leg Extension Power Asymmetry on Risk of Incident Recurrent Falls
| Asymmetry | Falls, n (%) | Minimally Adjusted Relative Risk (95% confidence interval) | Fully Adjusted Relative Risk (95% confidence interval) | |
|---|---|---|---|---|
| Leg extension power | Absent | 402 (10.2) | Reference | Reference |
| Present | 173 (13.1) | 1.21 (1.01–1.45) | 1.19 (0.99–1.43) | |
| Handgrip strength | Absent | 456 (10.8) | Reference | Reference |
| Present | 193 (13.4) | 1.20 (1.01–1.42) | 1.20 (1.01–1.43) |
Notes: Minimally adjusted models included age and clinic site. Fully adjusted models included baseline maximum leg extension power or maximum handgrip strength (for the appropriate predictor), age, clinic site, race, alcohol intake, cigarette smoking status, body mass index, cognitive functioning, physical activity participation, morbidities, and benzodiazepine usage.
Table 3 presents the results for the associations of HGS and LEP asymmetry with incident fractures. Participants in the highest HGS asymmetry quartile had a 1.41 (CI: 1.02–1.96) greater risk for hip fractures, 1.28 (CI: 1.04–1.58) greater risk for major osteoporotic fractures, and 1.24 (CI: 1.06–1.45) greater risk for nonspine fractures. More modest and generally nonstatistically significant associations were observed between LEP asymmetry and these fracture outcomes. Neither HGS nor LEP asymmetry were associated with clinical spine fractures. Supplementary Tables 2–5 provide the complete results from the fully adjusted models examining the associations of HGS and LEP asymmetry with incident hip, major osteoporotic, nonspine, and clinical spine fractures, respectively.
Table 3.
Associations of Leg Extension Power and Handgrip Strength Asymmetry on Incident Fractures
| Asymmetry | Fractures, n (%) | Minimally Adjusted Hazard Ratio (95% confidence interval) | Fully Adjusted Hazard Ratio (95% confidence interval) | |
|---|---|---|---|---|
| Hip fracture | ||||
| Leg extension power | Absent | 102 (2.5) | Reference | Reference |
| Present | 50 (3.7) | 1.26 (0.89–1.77) | 1.25 (0.88–1.78) | |
| Handgrip strength | Absent | 114 (2.7) | Reference | Reference |
| Present | 58 (4.0) | 1.43 (1.04–1.97) | 1.41 (1.02–1.96) | |
| Major osteoporotic fracture | ||||
| Leg extension power | Absent | 276 (6.9) | Reference | Reference |
| Present | 111 (8.3) | 1.13 (0.90–1.41) | 1.09 (0.86–1.36) | |
| Handgrip strength | Absent | 299 (7.0) | Reference | Reference |
| Present | 129 (8.9) | 1.25 (1.02–1.54) | 1.28 (1.04–1.58) | |
| Nonspine fracture | ||||
| Leg extension power | Absent | 513 (12.8) | Reference | Reference |
| Present | 207 (15.5) | 1.21 (1.03–1.42) | 1.15 (0.97–1.36) | |
| Handgrip strength | Absent | 554 (12.9) | Reference | Reference |
| Present | 229 (15.8) | 1.22 (1.05–1.43) | 1.24 (1.06–1.45) | |
| Clinical spine fracture | ||||
| Leg extension power | Absent | 96 (2.4) | Reference | Reference |
| Present | 35 (2.6) | 1.05 (0.71–1.55) | 1.01 (0.68–1.52) | |
| Handgrip strength | Absent | 106 (2.5) | Reference | Reference |
| Present | 36 (2.5) | 0.99 (0.68–1.44) | 1.03 (0.70–1.51) |
Notes: Minimally adjusted models included age and clinic site. Fully adjusted models included baseline maximum leg extension power or maximum handgrip strength (for the appropriate predictor), age, clinic site, race, alcohol intake, cigarette smoking status, body mass index, cognitive functioning, physical activity participation, morbidities, benzodiazepine usage, and femoral neck bone mineral density.
Supplementary Table 6 shows the results for the associations of both HGS and LEP asymmetry in the same models with risk of incident recurrent falls. Neither HGS nor LEP asymmetry, when in a model together, were associated with incident recurrent falls. Further, Supplementary Table 7 presents the results for the associations of both HGS and LEP asymmetry in the same models for incident fractures. Older men in the highest HGS asymmetry quartile had a 1.19 (CI: 1.01–1.41) greater risk for nonspine fractures, but older men in the highest LEP asymmetry quartile did not have a significantly greater risk for nonspine fractures despite a similar magnitude in the association (hazard ratio: 1.14; CI: 0.96–1.35). When included in the same models, neither HGS nor LEP asymmetry were associated with hip, major osteoporotic, and clinical spine fractures.
Discussion
The principal results of this study revealed that older men in the highest quartile of HGS asymmetry had an elevated risk for incident recurrent falls, hip fractures, major osteoporotic fractures, and nonspine fractures. While the association between men in the highest LEP asymmetry quartile and incident recurrent falls was not statistically significant, the magnitude of the association was similar to that of the association between HGS asymmetry and incident recurrent falls. We also observed more modest, and generally nonsignificant associations, between LEP asymmetry and each of the fracture outcomes. Our findings provide additional insights into how HGS and LEP asymmetries may factor into age-related mobility limitations and disability. Such insights could help us better understand the role of HGS and LEP asymmetries in examinations of muscle function, and how functional asymmetries, particularly for HGS, could be incorporated in fall risk assessments.
Physical measures that examine laterality may help to identify deficits in muscle function during aging. For example, gait disorder tests can help to identify the neuromuscular system deficits occurring on just one side of the body that contribute to fall and fracture risk (25). The fine motor skills, hand dexterity, and muscle coordination that is necessary for completing a maximal grip force task can similarly assess neuromuscular system functioning (26). As such, the neuromuscular dysfunction occurring on one side of the body that contributes to fall and fracture risk could similarly be observed by measuring HGS on both hands (14). Given that low HGS has already been shown to be associated with future falls and related fractures (27,28), functional asymmetries may reveal additional insights into predicting falls and recovery of physical performance tasks after fall-related fractures (29,30).
While our findings suggest that HGS asymmetry is associated with incident recurrent falls and fractures, asymmetric HGS is also linked to other fall-related outcomes. Fragala et al. (31) revealed that weak HGS and leg extension strength were associated with slow gait speed, and that either HGS or leg extension strength are appropriate for screening muscle weakness during aging. Moreover, measures of strength capacity that are collected from the upper extremities are similarly effective at predicting any fall with regards to muscle strength measured from the lower extremities (32). Measures of HGS and knee extension strength share the same underlying concept (maximal limb strength), and HGS could be regarded as a superior measurement based on procedural ease (33). Our findings for the association of HGS asymmetry on incident recurrent falls and fractures align with those completed previously (34), and may also help to elucidate why HGS asymmetry is associated with early all-cause mortality (15). Nonetheless, examining HGS asymmetry may provide specificity for how physical measures are associated with falls, thereby potentially increasing their clinical and translational research value.
Although HGS asymmetry may have factored into incident recurrent fall and fracture risk in our study, the results for LEP asymmetry should also be acknowledged. Our findings somewhat align with those from LaRoche et al. (35) who found that knee extensor power asymmetry is not related to functional mobility in older adults. The sit-to-stand test is a valid measure of bilateral lower limb power that is more robustly associated with physical performance than LEP (36). Given that HGS and LEP are relatively compatible for predicting mobility outcomes (31), HGS and related asymmetry assessments could be recommended based on procedural ease, economic feasibility, and scalability. Since the size of the effect estimates for HGS and LEP asymmetries for falls were similar (although only HGS asymmetry reached statistical significance), another explanation for our findings could be that HGS asymmetry is measured with greater precision than LEP asymmetry, and increased data availability exists for HGS asymmetry because of measurement simplicity.
Measures of HGS are a convenient and reliable measure of muscle function (37). Given that low strength capacity is a risk factor for future falls and related fractures (27,28), examining functional asymmetries may complement strength capacity assessments and represent a novel muscle function biomarker that is relevant to fall-related outcomes. For example, muscle strengthening activities that account for both improving functional asymmetries and strength reduced more future falls than muscle strengthening activities alone (38). Although low muscle function precedes deficits in physical performance, measures of muscle function, including asymmetry, are not considered in fall risk assessments (3). Examining muscle function as part of fall risk assessments may help to better identify the neuromuscular dysfunction that contributes to the physical performance deficits that are linked to falls and related injuries (5). Moreover, recognizing low muscle function will allow for fall prevention programs such as STEADI to intervene earlier, which in turn, may increase the efficacy of such programs. Therefore, we recommend that measures of muscle function be considered in fall risk assessments, including HGS asymmetry.
While a causal association between low HGS and early all-cause mortality may exist (39), our findings and experimental design are not supportive of a causal association between functional asymmetries and fall outcomes. Measures of HGS could be more sensitive in identifying the age-related neuromuscular dysfunction and poor coordination that contributes to falls (26). The mechanical and functional motor changes that may explain why strength asymmetries are associated with falls and related outcomes remain not well understood. More research into improving how we assess muscle function in clinical and translational research settings may reveal the mechanical and functional motor change pathways that contribute to falls and related fractures. Such work may help to mitigate the rapidly growing health burden of falls in the United States (1).
Some of our study limitations should be noted. The MrOS study consists of older men that identify as White race, so our findings have limited generalizability to older women and persons that identify as non-White. Lower cases of falls and fractures may have influenced the estimates from our regression models. Given that LEP is regarded as less feasible to measure than HGS, fewer participants had data for LEP asymmetry. Calculations for asymmetry could not be conducted for participants with only one HGS or LEP measure. Future studies on this topic that have greater diversity in participant demographics and higher sampling could help to fulfill some of our study limitations.
Conclusions
This investigation found that older men with higher HGS asymmetry could be at risk for recurrent falls and fall-related fractures. More modest, yet nonsignificant associations were found between LEP asymmetry and recurrent falls and fractures. HGS asymmetry should be evaluated as an addition to fall risk assessments, especially given the feasibility for HGS. More research is warranted for evaluating how HGS and LEP asymmetry may better operationalize muscle function, improve screening for age-related mobility limitations and disability, and factor into the disabling process.
Supplementary Material
Funding
The Osteoporotic Fractures in Men (MrOS) study is supported by National Institutes of Health (NIH) funding. The following institutes provide support: National Institute on Aging (NIA), National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS), National Center for Advancing Translational Sciences (NCATS), and NIH Roadmap for Medical Research under the following grant numbers: U01 AG027810, U01 AG042124, U01 AG042139, U01 AG042140, U01 AG042143, U01 AG042145, U01 AG042168, U01 AR066160, and UL1 TR000128.
Conflict of Interest
None declared.
Author Contributions
R.M. conceived and designed the study, informed analyses, interpreted the results, and wrote the manuscript; T.L.B. conducted the analyses, interpreted the results, and revised the manuscript; K.E.E. informed analyses, interpreted the results, and revised the manuscript; B.M.V. interpreted the results and revised the manuscript; P.M.C. conceived and designed the study, informed analyses, interpreted the results, and revised the manuscript.
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