Epidemiology of hip fractures in Siena, Italy, 1975-1985.

A survey of 1567 fractures of the proximal end of the femur due to minor trauma occurring in elderly people was performed. The fracture incidence rate per 100,000 individuals in the population at risk was calculated. Hip fracture prevailed in women with a sex ratio of women to men of 3.81; in both sexes the incidence was more closely related to age than any other factor. The incidence rate of fracture increased significantly in women during the period from 1975 to 1985, whereas there was no significant increase in men during this time. This change may be related to the continuing trend toward a greater proportion of elderly women in the population. The incidence rate in men showed a long-cycle periodic behavior correlated with the long-cycle trend of cloud cover and rainfall; it is possible that precipitation and a greater occurrence of femoral fractures might be interrelated in men. This parallelism was not evident in women. In women the rise in fracture rate was not continuous but decreased periodically. The zeniths of fracture incidence were preceded two years by a decrease in temperature and an increase in cloud cover and rainfall, suggesting a possible relationship between fractures and the diminution of ultraviolet radiation.