Disability progression in RRMS not always permanent, study finds

A new study has found that disability progression in relapsing remitting MS is not always permanent, even when it happens without a relapse. This type of progression is known as progression independent of relapse activity, often shortened to PIRA. The research shows that almost one third of people living with RRMS who experience PIRA later see some easing of disability.

RRMS is the most common type of MS. People often have relapses where symptoms get worse, followed by periods where they settle again. Although relapses can play a part in long term disability, some people also experience PIRA, which is when disability increases for at least six months but is not linked to a relapse.

For many, PIRA leads to a lasting increase in disability. However, this new analysis shows that for a significant number of people, disability can ease again over time. The team looked at data from the MSBase registry, which holds long term information from thousands of people living with MS around the world.

The study included 4,713 people with RRMS who experienced PIRA between 1995 and 2024. After a median follow up of nearly nine years, around 68 percent had no improvement in disability after their PIRA event. The remaining 32 percent experienced a sustained reduction in disability, usually beginning about two and a half years later.

People whose disability eased again had a much lower risk of reaching more severe disability levels. They also had a far lower chance of moving on to secondary progressive MS. The analysis showed an 81 percent lower risk of reaching an EDSS score of six, which indicates significant walking difficulties, and an 82 percent lower risk of transitioning to secondary progressive MS.

The researchers found that younger people and those with lower disability scores at the start of the study were more likely to experience improvements after PIRA. People using highly effective disease modifying therapies also had a reduced risk of long-lasting PIRA. The team reported that those on high efficacy treatments were 22 percent more likely to see their disability improve again.

The researchers say these findings suggest that some disability progression in RRMS is not fixed and may ease over time. They also highlight the possible role of effective treatments in reducing long term progression. More research is needed to understand why PIRA behaves differently from person to person and how treatments might influence these changes.