[Epidemiological study on hip fractures in Tottori Prefecture].

These days, hip fractures are becoming serious health problem in elderly people. We have, therefore, conducted an epidemiological study in Tottori prefecture, Japan on the following elements related to the hip fracture of patients: the incidence, cause, environment, state of individual health, outcome and risk factors. We obtained data from hospital records and from hip fracture patients by mailed questionnaires. The incidence of hip fractures per 100000 person-years was 67.8 and 165.9 for male and female 50 years of age and older. This incidence is a half or one-third of that in North Europe or North America. We assume that the difference of physique and life style between Japanese and Caucasian have some effect on incidence. Almost all fractures occurred by falling over from a standing position. The incidence of distal radius fracture in past history is four times more frequent in female patients compared to that in males. About 12% of male and 19% of female patients aged 60 and over with hip fracture were demented before the injury. The case-control study revealed that thin figure and bed-ridden were significant risk factors for the hip fracture. Thin figure was more prevalent in the group with cervical fracture than that with the trochanteric fracture. Analyzing our data with the Cox proportional hazards model, our study has shown that male, aging and dementia were important factors in determining the life expectancy of patients with hip fracture.