Seasonal variation of femoral fractures in the state of São Paulo, Southeast Brazil

OBJECTIVE: To examine the effect of seasonality on femoral fracture incidence among people residing in the state of São Paulo, Brazil. METHODS: Ecological study based on a consecutive series of 216,348 reports of hospital admissions caused by femoral fractures. A Bayesian statistical model was used for time series analysis, considering the monthly average number of events of femoral fractures per day as a dependent variable. RESULTS: Among the female population, significant seasonal effects were observed only for older women, aged 60 years or more. Among younger men (aged less than 20 years) there is not a clear seasonal effect, but among the other age groups there seems to exist a higher number of cases of femoral fractures during the coldest months of the year. CONCLUSIONS: In general, more cases of fractures occur during the coldest months of the year; however, men and women have different patterns of incidence according to each age group.