In one of the first studies to examine how multiple sclerosis relapses affect people during different time periods of the disease, researchers found that people with multiple sclerosis who have relapses within the first five years of onset appear to have more severe disability in the short term compared to people who do not have an early relapse.

Eighty five percent of people with multiple sclerosis begin by having the relapsing-remitting form of the disease and the majority of these people later develop secondary progressive multiple sclerosis. A relapse is defined in the study as worsening of neurological symptoms for more than 24 hours, without a fever or infection. Because relapse-related symptoms often improve within a few weeks, it's been unclear how much disability comes from relapses, and how much from progression.

The researchers reviewed the medical records of 2,477 people with multiple sclerosis who experienced relapses. The study looked at whether the participants had disability severe enough to require the use of a cane for walking and whether this was related to relapses occurring within five years, five to 10 years, or more than 10 years after onset of symptoms. The participants were followed for an average of 20 years and during that time the group experienced 11,722 relapses.

They found that multiple sclerosis patients who had a relapse within five years of disease onset were at a 48 percent higher hazard (a measure of relative risk) of needing a cane to walk within five years of disease onset than those who did not have an early relapse. Importantly, the impact of the early relapse lessened over time. Those with early relapse who did not need a cane after five years were at only a 10 percent higher hazard (a measure of relative risk) of needing one 10 years after disease onset than those without early relapses.

"Our findings may represent an important message to people diagnosed with multiple sclerosis today. Those who have a history of relapses could potentially be offered reassurance that as time goes on, these relapses will have a diminishing effect on their everyday lives," said study author Helen Tremlett. "In addition, our study calls upon the need for new medications that target axonal degeneration, which is suspected of causing permanent disability, especially for people who have had multiple sclerosis for many years or who are older at diagnosis."

The impact of relapses that occurred later, either at five to 10 or more than 10 years after the start of the disease, also waned over time and became insignificant after long-term follow up. Relapses in people under 25 had a longer impact on disability compared to those over 35 years.

"There may be a longer window of opportunity for treating younger people with multiple sclerosis right away, changing the course of progression later on," Tremlett said.
References:
1. H. Tremlett, et al. Impact of multiple sclerosis relapses on progression diminishes with time. Neurology, doi: doi:10.1212/WNL.0b013e3181c1e44f.