Comparison of performance-based measures among native Japanese, Japanese-Americans in Hawaii and Caucasian women in the United States, ages 65 years and over: a cross-sectional study.

Kiyoshi Aoyagi,Philip D Ross,Richard D Wasnich,Tai-Ichiro Takemoto,Michael C Nevitt,Takuo Hayashi,James W Davis

doi:10.1186/1471-2318-1-3

Abstract

BackgroundJapanese (both in Japan and Hawaii) have a lower incidence of falls and of hip fracture than North American and European Caucasians, but the reasons for these differences are not clear.Subjects and MethodsA cross-sectional study. We compared neuromuscular risk factors for falls using performance-based measures (chair stand time, usual and rapid walking speed, and grip strength) among 163 Japanese women in Japan, 681 Japanese-American women in Hawaii and 9403 Caucasian women in the United States aged 65 years and over.ResultsAfter adjusting for age, the Caucasian women required about 40% more time to complete 5 chair stands than either group of Japanese. Walking speed was about 10% slower among Caucasians than native Japanese, whereas Japanese-American women in Hawaii walked about 11% faster than native Japanese. Grip strength was greatest in Japan, which may reflect the rural farming district that this sample was drawn from. Additional adjustment for height, weight or body mass index increased the adjusted means of chair stand time and grip strength among Japanese, but the differences remained significant.ConclusionsBoth native Japanese and Japanese-American women in Hawaii performed better than Caucasians on chair stand time and walking speed tests, and native Japanese had greater grip strength than Japanese in Hawaii and Caucasians. The biological implications of these differences in performance are uncertain, but may be useful in planning future comparisons between populations.

Highlights

Japanese have a lower incidence of falls and of hip fracture than North American and European Caucasians, but the reasons for these differences are not clear
The sample of Japanese-Americans living in Hawaii were women who participated in the Hawaii Osteoporosis Study (HOS) Examination 8, conducted between 1992 and 1994
Male subjects of the HOS were recruited from the Honolulu Heart Program (HHP), which is a prospective cohort study of coronary heart disease and stroke among men of Japanese ancestry born between 1900–1911 and living on the island of Oahu, Hawaii in 1965

Summary

Introduction

Japanese (both in Japan and Hawaii) have a lower incidence of falls and of hip fracture than North American and European Caucasians, but the reasons for these differences are not clear. North America or northern Europe [2,3,4] This lower fracture rate among Japanese is not explained by greater bone mass [5,6,7,8,9]. The lower fracture rates might have resulted from a lower prevalence of risk factors for fractures among Japanese. We reported earlier that the incidence and prevalence of falls among Japanese (both in Japan and Hawaii) is approximately half that of Caucasians in North America and Britain [12,13], but the reason for these differences are not clear

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