Weather conditions and their effect on seasonality of incident osteoporotic hip fracture.

ABSTRACT

Our aim was to analyze the seasonality and the effect of weather conditions on the incidence of osteoporotic hip fracture in a Southern European region. INTRODUCTION: The objective of this work is to evaluate seasonality and the effect of weather conditions on the incidence of osteoporotic hip fracture in a Southern European region. METHODS: This retrospective cohort study included all patients admitted to Alcorcón Foundation University Hospital with a diagnosis of osteoporotic hip fracture between the years 1999 and 2015. In a time series analysis, we examined the association between hip fracture incidence and different weather conditions and seasonality using general additive models (with Poisson distribution). The incidence rate ratio (IRR) crude and adjusted by season was estimated for all parameters. Hip incidence was further analyzed by sex and age (below or over 75) subgroups. RESULTS: Four thousand two hundred seventy-one patients with an osteoporotic hip fracture were included (79% females, mean age 83.8). Season fracture rate was significantly higher in fall and winter (67.06 and 64.41 fractures/season) compared to summer and spring (59.71 and 60.06; p < 0,001). Hip fracture incidence was 15% greater in autumn and winter than in spring and summer. Fog [IRR 1.15 (95% CI 1.003-1.33)], atmospheric pressure (per 100 mb) [IRR 1.05 (95% CI 1.004-1.114)], and frost [IRR 1.15 (95% CI 1.03-1.30)] were significantly associated with increased hip fracture. Haze [IRR 1.10 (95% CI 0.99-1.23)] showed a trend without statistical significance. Daily average temperature (per 5 °C) [IRR 0.98 (95% CI 0.957-0.996)], rain (per 10 ml) [IRR 0.99 (95% CI 0.981-1.0)], wind speed [IRR = 0.952, (95% CI 0.907-0.998)], and daily ultraviolet radiation (per 100 joules) [IRR 0.998 (95% CI 0.996-1.0)] were negatively associated with fracture. After adjusting by season and trend, all these associations disappear. CONCLUSIONS: In this Southern region, hip fracture incidence exhibits a seasonal pattern different from those communicated in Northern regions. There is short-term association with different weather conditions that partly explain this seasonal pattern.