Obese people with multiple sclerosis (MS) had faster disability accumulation, greater cognitive declines, and worse quality of life in the 15 years after diagnosis relative to patients with normal weight, according to an analysis of Swedish data.

While it’s been known that obesity was a risk factor for developing the neurodegenerative disease, the findings shed more light on how it influences its course after a diagnosis.

Lars Alfredsson, PhD, a professor at the Karolinska Institutet in Sweden, presented the data in an oral presentation at the European and American Committees for Treatment and Research in Multiple Sclerosis (ECTRIMS-ACTRIMS) meeting, held Oct. 11-13 in Milan, Italy and online. The talk was titled, “Obesity negatively affects disease progression, cognitive functioning, and quality of life in people with multiple sclerosis.”

Obesity is associated with chronic inflammation that can increase the risk of autoimmune diseases like MS. Indeed, obese children or teens are about twice as likely to develop MS than non-obese people.

Less is known about how obesity influences disease progression after a diagnosis, however. Some studies suggest it may worsen MS severity or accelerate nerve degeneration.

Obesity and MS disability progression

Researchers here examined obesity’s influence on disease progression, cognition, and quality of life among MS patients in Sweden included in a nationwide study between 2005-2019.

When they were included, the patients completed an extensive questionnaire related to lifestyle and environmental factors. A similar questionnaire in 2021 sought to assess any changes.

The final analysis included 3,249 MS patients with a mean age of 37.8, 74% of whom were women. They were followed for up to 15 years after their diagnosis through the Swedish MS registry, where they were monitored for changes in disability, quality of life, and cognition.

Obesity was determined based on body mass index (BMI), a proxy indicator of body fat based on height and weight. Normal BMI ranges from 18.5-24.99, overweight is 25-30, and higher than 30 is obese. Disability progression was monitored with the Expanded Disability Status Scale (EDSS), a scale of 0-10 where increasing scores reflect greater disability.

Compared with patients of a normal weight, obese MS patients exhibited a .022-point faster annual increase in EDSS scores, reflecting a faster disability progression. While that difference is “not very large,” it was statistically significant, according to Alfredsson.

Obesity was associated with a 41% higher risk of reaching an EDSS score of 3, which generally marks a shift from no or minimal disability to moderate disability, and a 31% higher risk of reaching 4, which marks significant disability without walking impairments.

The analyses took factors like age, sex, disease type, disease duration, disability, therapies, and smoking into account that may have had an effect.

On the other hand, “overweight is not associated with an increased risk, which is an important information,” Alfredsson noted.

Obese patients were found to be at a higher risk of quality of life declines. Specifically, it was associated with a 40% higher risk of physical worsening and a 24% higher risk of psychological worsening — defined as at least a 7.5-point increase for either component on the Multiple Sclerosis Impact Scale 29 (MSIS29).

Among the subset of patients who didn’t have a BMI change during the follow-up, differences in disability and quality of life were even greater than among the overall study population.

For example, the risk of reaching an EDSS of 3 was 50% higher for patients who were obese for the entire follow-up compared with those who always had a normal weight. Also, obesity increased the risk of physical worsening by 70% and of psychological worsening by 36%, compared with normal weight.

Obese participants whose BMI didn’t change over the follow-up were at a 47% higher risk of cognitive worsening, defined as at least an 8-point increase in the Symbol Digit Modalities Test (SDMT), compared to those who weren’t obese.

Overall, “obesity appears to negatively influence both disease progression, health-related quality of life, and cognitive functioning in persons with MS,” Alfredsson said.

The researchers noted the study had among its strengths that there were a large number of patients with follow-up data in the Swedish MS register. A limitation was that BMI was self-reported and not objectively measured.

Note: The Multiple Sclerosis News Today team is providing in-depth coverage of the 9th joint ECTRIMS-ACTRIMS meeting Oct. 11-13. Go here to see the latest stories from the conference.