Weather, Weather Changes and the Risk of Bell's Palsy: A Multicenter Case-Crossover Study.

BACKGROUND: To evaluate if weather or changes in weather are risk factors for Bell's palsy (BP) as exposure to draught of cold air has been popularly associated with the occurrence of BP.

METHODS: Using a multicenter hospital-based case-crossover study, we analyzed the association between ambient temperature, atmospheric pressure, relative air humidity or their 24 h changes and the risk for BP in 825 patients or subgroups.

RESULTS: One day following a 24 h increase in atmospheric pressure of more than 6 hPa, the risk for BP increased by 35% (OR 1.35; 95% CI 1.03-1.78) in the overall population. The risk for BP more than doubled in patients with diabetes mellitus after rapid variations in ambient temperature, independent of the direction (temperature decrease > 2.25°C; OR 2.15; 95% CI 1.08-4.25; temperature increase between 0.75 and 2.25°C; OR 2.88; 95% CI 1.63-5.10).

CONCLUSIONS: Our findings support the hypothesis of an association between certain weather conditions and the risk for BP with acute changes in atmospheric pressure and ambient temperature as the main risk factors. Additionally, contrasting results for risk of BP after temperature changes in the diabetic and non-diabetic subgroups support the paradigm of a diabetic facial palsy as a distinct disease entity.