MS prevalence rise tied largely to longer survival after diagnosis, study finds
France, Sweden data show new diagnosis rates were stable to modestly declining
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A new study found that rising MS prevalence in France and Sweden appears to be driven largely by longer survival after diagnosis, rather than by an increase in new cases. (Photo by iStock)
- Multiple sclerosis prevalence is rising largely due to longer patient survival.
- New MS diagnoses are stable to slightly declining.
- Improved survival may be linked to better clinical management and disease-modifying therapies.
The number of people living with multiple sclerosis (MS) has risen steadily over the past two decades, but the increase appears to be driven largely by longer survival after diagnosis rather than by more people developing the disease.
That’s according to findings of a large study that analyzed nationwide health data from France and Sweden, with main trend analyses spanning 2003 to 2022 across the two countries. Researchers found that while the total number, or prevalence, of people living with MS increased substantially over time, the rate of new diagnoses — known as incidence — showed a modest decline.
Longer survival may explain rising MS prevalence
“In short, we are diagnosing roughly as many MS cases today as twenty years ago. But patients are living significantly longer thanks to better clinical management and therapies that can alter the trajectory of the disease,” Thomas Nedelec, PhD, a research scientist at the Paris Brain Institute and one of the study’s senior authors, said in an institute news story.
The study, “Drivers of Rising Prevalence in Major Motor Neurodegenerative Diseases: Temporal Trends in Sweden and France (2003–2022),” was published in Neurology.
Like Parkinson’s disease and amyotrophic lateral sclerosis (ALS), MS is a chronic neurological disease that can progressively impair movement and significantly affect quality of life. As a result, these conditions place a substantial burden on patients, caregivers, and healthcare systems.
The number of people living with these diseases has been increasing worldwide, but the reasons behind this trend remain unclear. Understanding whether the increase is driven by higher incidence, longer survival, or other factors can help researchers and policymakers better anticipate healthcare needs, allocate resources, and plan future care.
With this in mind, researchers in France and Sweden set out to investigate how the burden of MS has changed over time by analyzing prevalence, incidence, age at diagnosis, and life expectancy at diagnosis. They did the same for Parkinson’s and motor neuron diseases (MNDs), a group of disorders that includes ALS.
Researchers analyzed national health data
The analysis drew on national health registries covering nearly the entire populations of both countries. The underlying cohorts included residents in Sweden from 2001 to 2016 and in France from 2009 to 2022, with main trend analyses covering 2003-2016 in Sweden and 2011-2022 in France.
Across both countries, the number of people living with MS increased substantially over time. In Sweden, the MS population grew from 12,457 people in 2003 to 19,864 in 2016. In France, it rose from 94,438 people in 2011 to 130,676 in 2022. Pooled data showed that the number of people living with MS increased by an average of 2.9% each year.
New diagnoses followed a different pattern, however. In France, incidence showed a modest decline, going from 8.2 cases per 100,000 people each year in 2011 to 7.2 in 2022. In Sweden, incidence also fell from 11.2 cases per 100,000 people per year in 2006 to 9.7 in 2016.
When data from both countries were combined, researchers found a significant overall decline in the rate of new diagnoses over time.
The team noted, however, that part of the decline may reflect how cases were identified in national health records. Some people who had already been living with MS but rarely sought medical care may initially have been counted as newly diagnosed cases, making incidence appear higher in the early years of the study.
The median age at diagnosis remained largely stable overall, although it fell by about five years in Sweden, from 45.3 years in 2003 to 40.3 years in 2016.
MS survival improved over study period
At the same time, survival improved significantly. Among people diagnosed with MS in 2013-2014, estimated life expectancy after diagnosis was 33.2 years in Sweden and 37.6 years in France. Across the full study period, life expectancy after an MS diagnosis increased by an average of 2.35 months per year, outpacing gains seen in the general population.
Taken together, the findings suggest that the growing number of people living with MS is being driven primarily by longer survival rather than by an increase in the number of people developing the disease. The researchers said advances in disease management and the widespread use of disease-modifying therapies likely contributed to these gains.
“Our finding on the rising prevalence of MS corroborates and extends recent studies in developed Western countries, confirming an ongoing trend of increasing prevalence in line with improved survival,” the researchers wrote.
The pattern differed for the other neurological diseases included in the study. For motor neuron diseases, a group that includes ALS, prevalence rose as new cases increased, a rise the researchers said was partly explained by population aging. Parkinson’s, meanwhile, showed a more modest rise in prevalence despite declining incidence rates, a trend the researchers suggested may reflect a plateau in the survival gains seen in previous decades.
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