Effect of atmospheric factors on the incidence of Bell's palsy.

To assess the possible influence of atmospheric factors on the incidence of Bell's palsy, a retrospective case review of patients seen between 1 January 1992 and 30 June 1996, was designed. The population included all Bell's palsy patients in whom the exact date of onset of paralysis (day, month, year) was known. The following parameters were registered daily by the Spanish National Service of Meteorology throughout the period of survey: temperature, atmospheric pressure and air pollutants (total number of particles and levels of SO2, CO, O3, NO2, NO, CH4 and total organic carbon). The only factor significantly related to Bell's palsy was temperature (P = 0.0164). Lower temperatures were associated with a higher incidence of Bell's palsy. A relationship between atmospheric pressure and/or air pollutants and Bell's palsy was not found.