Inclement weather and the risk of hip fracture.

An association between inclement weather and hip fractures has been documented, but specific subgroups of the population at particular risk have not been identified. We obtained information that included hospitalization data on all hip fractures in Montreal from 1982 to 1992, and meteorologic data on the amount of snow, rain, and freezing rain and the temperature on each day of study. We used a cross-level design to examine the association between the rate of hip fractures and the meteorologic conditions on the day of the accident in both sexes and five age strata. There were a total of 18,455 hip fractures over the 4,018-day study period. We found a cyclical pattern in occurrence of hip fractures, with the peak occurring in mid-December among women and the first week of January among men. The pattern was less pronounced among women than men, with peak-to-trough ratios of 1.2 and 1.4, respectively. Days with lower temperatures, snow, and freezing rain were associated with increased rates of hip fracture. The meteorologic condition carrying the greatest risk was freezing rain. The association between inclement weather and hip fractures was stronger among younger persons, both women and men. After adjusting for meteorologic variables, there remained increases in winter of 5% among women and 12% among men. The residual effect of winter may be related to cold temperatures or due to an accumulation of ice and snow even on fine days. Other possible mechanisms to explain the residual effect of winter include slower reaction times and winter bone loss, both of which could affect indoor as well as outdoor falls.