Weather Conditions and Multiple Sclerosis Relapse: Understanding the Dynamics

A Polish cohort study found that specific weather conditions—higher ambient temperatures and rapid drops in relative humidity—were associated with the timing of multiple sclerosis relapses.

Prior evidence on weather–MS relationships has been inconsistent. This analysis improves temporal granularity and uses explicit meteorological parameters matched to relapse onset dates, which reduces ecological ambiguity. Plausible mechanisms include transient heat sensitivity in demyelinated axons, dehydration-related physiologic stress, and short-lived immunologic activation; causation is not established.

The cohort review captured 80 verified relapses (2015–2023) and used relapse onset timing as the primary endpoint, with local meteorological records linked to each event. The investigators observed a distinct spring–summer relapse peak alongside consistent associations between relapse onset days and higher daily maximum temperature, lower relative humidity, reduced rainfall probability, greater insolation, and short-term pressure fluctuations.

Temperature, relative humidity, and short-term barometric variability emerged as the most informative meteorological predictors and could be incorporated into short-window time-series models or moving-window risk scores. Local meteorological feeds and public weather-station APIs provide readily available inputs for prototype models; simple threshold-based alerts or probabilistic short-term risk forecasts could complement clinical monitoring. Prospective evaluation and local calibration are required before clinical deployment.

Clinicians can counsel patients that warm, dry periods—particularly late spring and early summer—were associated with increased relapse occurrence in this cohort, and that maintaining hydration and active heat-management may reduce symptomatic stress during these periods. Flagging new neurologic signs during warm, dry spells can guide situational monitoring and patient counseling. These associations support targeted education and situational monitoring tied to meteorological conditions.