Risk factors for hip fracture in a Japanese cohort.

Risk factors for hip fracture were determined from a Japanese cohort. A cohort of 4573 people (mean age 58.5 +/- 12.2) who participated in the Adult Health Study in 1978-1980 were subsequently followed by biennial examinations up to 1992. Fifty-five incident hip fractures not due to traffic accidents were identified by medical records during the follow-up period. Poisson regression analysis showed that baseline low body mass index (BMI), regular alcohol intake, prevalent vertebral fracture, and having five or more children significantly increased the risk of hip fracture, and low milk intake and later age at menarche were marginally associated with increased fracture risk, after multivariable adjustment. Regular alcohol intake doubled the risk of hip fracture (relative risk 1.91, 95% confidence interval 1.07-3.42). Those individuals who had a vertebral fracture had 2.6 times higher risk than those who did not. The risk was 2.5 times higher among women who had five or more children than women with one or two. Body height, health status, marital status, intake of fish, coffee, tea, Japanese tea, smoking, exposure to atomic bomb radiation, and age at menopause were not associated with hip fracture. Relative risk for hip fracture decreased with decreasing number of preventable risk factors (low BMI, low milk intake, and regular alcohol intake). We conclude that many factors, such as BMI, milk intake, alcohol intake, prevalent vertebral fracture, age at menarche, and number of children, are related to the risk of hip fracture, and prevention programs need to focus on reducing preventable risk factors.