A cross-cultural comparison of neuromuscular performance, functional status, and falls between Japanese and white women

Abstract

Background: Previous studies have reported that the incidence of falls among Japanese women is about half that of white women. The difference in incidence might result from differences in neuromuscular performance, such as muscle strength, mobility, and balance. This hypothesis was tested by comparing two community-dwelling populations: Japanese women in the Hawaii Osteoporosis Study, and Caucasian women in the Study of Osteoporotic Fractures.

Methods: Neuromuscular performance was assessed for women in the two cohorts using standardized procedures. Falls were monitored longitudinally, using surveys mailed at 4-month intervals.

Results: The Japanese and white women differed substantially in their neuromuscular performance. The Japanese women had faster walking speeds and chair stands, and performed better on a series of balance tests. The white women had greater strength, particularly at the quadriceps, and faster hand and foot reaction times. The white women also reported fewer functional disabilities, including fewer difficulties in climbing steps, doing heavy housework, and shopping for groceries. In age-adjusted analyses, the risk of falls was greater for the white women [odds ratio (OR) = 1.8; 95% confidence interval (CI) = 1.6, 2.0]. After adjusting for the neuromuscular test results and the number of functional disabilities, the odds ratio for the risk of falls remained essentially the same (OR = 1.8; 95% CI = 1.5, 2.1).

Conclusions: The Japanese and white women had different advantages and limitations in neuromuscular performance. These differences, however, did not explain the lower risk of falls among Japanese women.