Short-term ambient temperature increases are associated with higher mortality in amyotrophic lateral sclerosis: a case-crossover study of weather conditions.

INTRODUCTION: Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disorder with vastly differing survival times. The influence of environmental exposures such as weather conditions on mortality among people living with ALS remain poorly defined. The aim of this study was to evaluate the association between short-term meteorological phenomena and the odds of death among patients with ALS. METHODS: We conducted a retrospective case-crossover study of 298 deaths among clinically verified ALS patients that occurred within a weather-station catchment area. Daily mean data for temperature, atmospheric pressure, and relative humidity were analyzed. Associations were analyzed by comparing hazard intervals (1-3 days before death) with bidirectional control intervals in generalized linear mixed models. Results are expressed as odds ratios (OR) and 95% confidence intervals (CI). RESULTS: Absolute meteorological conditions (temperature, pressure, humidity) showed no significant association with mortality, which was independently supported by seasonal/monthly death count analyses. Short-term temperature rises of 3 °C in the 24 h preceding the day before death were associated with 25% higher odds of death (OR 1.25; 95% CI 1.05-1.49). Exploratory subgroup analyses suggested that this association was most pronounced in female, ventilated, and older patients (≥65 years). Changes in relative humidity and atmospheric pressure were not significantly associated with the odds of death. CONCLUSION: Short-term temperature increases are associated with higher odds of death among people living with ALS, independent of absolute weather conditions or seasonal patterns. These findings support attention of stable ambient temperatures in end-stage care, while further studies of weather-related hazards in ALS are needed.