Short-term relationship between meteorological variables and hip fractures: an analysis carried out in a health area of the Autonomous Region of Valencia, Spain (1996-2005).

Introduction: Diverse studies have shown a seasonal influence on the incidence of hip fracture (HF), possibly associated with adverse meteorological conditions. In this paper, we present an analysis of the short-term relationship between meteorological conditions and the incidence of HF in people over 45 years of age living in a Mediterranean climate zone.

Material And Methods: HF cases admitted to the two reference hospitals in the health area were selected. The meteorological variables (temperature, relative humidity, rain, wind, and other conditions) were obtained from a weather station centrally located within the area under study. The trend and seasonality of the time series were analyzed with the aid of Poisson regression modeling. The relationship between the incidence of a hip fracture and the meteorological conditions, both on the same day and on the day previous to the patient's admission to the hospital were correlated in a case-crossover analysis with the control periods selected in accordance with two different methods of approximation (symmetric and semi-metric). The results were analyzed for different subgroups defined by age (older or younger than 75 years of age) and sex of subject and by type of fracture (cervical or pertrochanteric).

Results: 2121 patients admitted for HF were selected. Of these, 1598 (75.3%) were women and 523 (24.7%) were men. The average age of the subjects was 80, with patients ranging from 45-99 years of age. The time/weather series showed a positive tendency, with a greater occurrence of cases in the autumn and winter months. The case-crossover analysis showed a significant relationship between the daily duration of wind and the incidence of HFs. Divided into quartiles, the windiest days (quartile 4) were associated with a 32% increased risk of HF (OR 1.32 CI 95% 1.10-1.58) with respect to the calmest days (quartile 1), especially in patients under 75 (OR 1.53; CI 95% 1.02-2.29). The remaining meteorological variables were not associated in any significant fashion with the incidence of HFs. The results were comparable across different subgroups classified by age, sex, and type of fracture.

Conclusions: The incidence of HFs varies seasonally and presents a significant association with the coldest times of the year. In the short-term, lasting windy periods are associated with an increased risk of HFs whereas other meteorological variables show a much lower, non-significant correlation.