Study identifies time of year most common for MS relapses

Relapses in people living with relapsing remitting multiple sclerosis (MS) may happen more often during spring and summer, according to new research from Poland. The study suggests this increase may link to warmer temperatures, lower humidity, and bigger changes in air pressure.

Researchers also found that stressful life events and infections were the most commonly reported possible triggers for a relapse.

The study looked at relapse patterns and local weather conditions to better understand what might influence changes in symptoms. The researchers noted that recognising these factors could help shape future research and support a more informed approach to managing MS.

Researchers reviewed relapse records from 80 people living with relapsing remitting MS who received care at a single hospital. They compared the dates of relapses with weather data from the days leading up to symptom onset.

On average, participants had lived with MS for around 10 years, and most were taking disease modifying treatments.

Between 2015 and 2020, relapses occurred most often in March, June, July, and October. When grouped by season, spring and summer showed the highest number of relapses. From 2021 to 2023, relapses increased in May and February, with spring again showing the highest numbers and autumn the lowest.

Overall, relapses were more common during warmer months across both time periods studied.

For 15 people, a relapse marked the first signs of MS, following a diagnosis of clinically isolated syndrome. Different symptoms appeared more often at different times of year. Changes in sensation such as tingling or numbness were reported only by women and occurred most often in January. Optic neuritis, which can cause blurred or painful vision, peaked in March.

Muscle weakness and movement related symptoms appeared more frequently in May and June. Balance and coordination problems increased in March and July. Symptoms linked to spinal cord involvement, including weakness or bladder changes, appeared more often in August.

Around 62 per cent of participants reported at least one possible trigger for their relapse. Stressful life events and respiratory infections were the most common. A small number of relapses followed vaccination, pregnancy or the period after birth, or surgery.

When relapses began, weather conditions often differed from the monthly average. Temperatures tended to be higher, humidity lower, and rainfall less likely. Researchers also noted higher levels of sunlight and greater changes in atmospheric pressure than usual.

The team concluded that spring and summer conditions, particularly higher temperatures, lower humidity, and shifting air pressure, may contribute to relapse patterns. They stressed that more research is needed to fully understand these links and how they could support people living with MS in the future.