What happens when a patient with multiple sclerosis (MS) who is clinically stable stops taking their medication?

An international, multi-site study found almost 40 percent of patients had some disease activity return after they stopped, according to research presented at the American Academy of Neurology Annual Meeting last week.

"Despite long periods of disease stability while taking medication, we found a large minority of patients who stopped experienced relapses or disability progression," says lead study author Ilya Kister, MD, an assistant professor of neurology at the NYU Langone Multiple Sclerosis Comprehensive Care Center. "We need to identify situations when it is safe for patients with MS to stop taking these medications."

Little is known about MS disease progression after first-line, disease-modifying therapies are discontinued in clinically-stable patients.

For the study, Dr. Kister and colleagues prospectively studied 181 patients from the global observational MSBase Registry, examining MS relapse rates and disability progression rates in patients who stopped taking disease-modifying therapy.

Patients in the study were ages 40 and older, had experienced no relapses and reported stable disability progression (measured by EDSS scores) for at least 5 years, and had been taking medication for at least three years. Once medications were ceased, patients were followed for at least three years.

After discontinuing medication, 24 percent of patients experienced a clinician-reported relapse, 32 percent sustained three-month disability progression, and 10.6 percent of patients recorded both relapses and disability progression.

Researchers found 77 patients - or 42 percent - restarted medication after a median of 22 months. Restarting medication was associated with a 59-percent risk reduction of disability progression.

More than 2.3 million people worldwide are affected by MS, according to the National Multiple Sclerosis Society (NMSS). The unpredictable disease affects the central nervous system, causing disability that can range in severity, with symptoms including muscle weakness, pain, difficulty with coordination and balance, partial or complete paralysis, tremors and hearing and vision loss.

Medication can help to manage attacks, reduce symptoms, and slow the progression of multiple sclerosis. According to the NMSS, some people stop taking disease-modifying medication for reasons including side effects, perceptions they're not feeling better or because they still experience exacerbations, or insurance purposes.