One risk factor for falls in the elderly is muscle weakness; muscle strength is important in maintaining balance. Most systematic reviews that measure the magnitude of individual risk factors for falls have focused on drugs. In this systematic review, Moreland and colleagues investigated the quantitative contribution of muscle weakness to fall risk in elderly adults.
Criteria for study selection included age of the study sample, with at least one half of participants 65 years and older; muscle strength considered as an individual risk factor; and falling as a studied outcome. Prospective study design also was a requirement.
Of 30 reports that met the inclusion criteria, 13 contained data that could be extracted for analysis. The most common measures used to assess lower-extremity strength were knee extensions, ankle dorsiflexion, and chair stands. The combined odds ratio (OR) for these measures as a risk for falling was statistically significant at 1.76. For recurrent falls, the OR was 3.06.
In the case of upper-extremity strength testing, grip strength was the most common measure used for assessment. Here, the ORs were statistically significant, but of a lower magnitude than those for lower-extremity weakness. Another method of adjusted analysis, rate ratio, was used by one study. This showed a small effect size that was not statistically significant. A sensitivity analysis showed that institutionalized elderly patients were consistently at higher risk for falls than their community-dwelling counterparts when muscle weakness was present.
The authors conclude that lower-extremity weakness is a statistically significant risk factor for falls. Because adjusted analysis was provided in only one upper-extremity study, the association between upper-extremity weakness and falls may indicate simply that upper-extremity weakness is a marker for lower-extremity weakness. Other meta-analyses have found that pharmacologic agents, specifically psychotropic medications, are independent risk factors for falls. Although this study has identified muscle weakness as another independent risk factor, an important limitation is the fact that many of the studies reviewed did not report multivariate analyses. More important clinically, the literature does not provide strong evidence that muscle strengthening through various exercise regimens prevents falls. Thus, more work must be done to determine what aspect of muscle strength is protective.