MILAN – Swedish researchers reported at the 9th Joint ECTRIMS-ACTRIMS meeting.
In a group of 3,249 subjects tracked for up to 5 years (74% female; mean age, 37.8 years), patients who were obese at diagnosis were 1.41 times more likely than normal-weight patients to reach an Expanded Disability Status Scale (EDSS) score of 3. About 35% of 355 obese subjects (body mass index > 30 kg/m2) reached that level versus 29% of 713 overweight patients (BMI, 25-30) and 28% of 1,475 normal-weight patients (BMI, 18.5-24.99).
Among subjects whose BMI category didn’t change over follow-up, those who were obese at diagnosis were more likely to develop cognitive worsening than those who weren’t obese (hazard ratio, 1.47, 95% confidence interval, 1.08-2.01).
Lars Alfredsson, PhD, a professor at the Karolinska Institutet, Stockholm, who presented the study findings, said in an interview that they fill a gap in knowledge about obesity and MS. “It is known that obesity around the age of 20 or in adolescence is a risk factor for developing MS. But much less is known in regard to progression, and the studies have been very inconclusive.”
The researchers tracked patients via the Swedish MS registry: 1,475 of normal weight, 713 overweight, and 355 obese. Before adjustment for factors such as age, gender, and baseline EDSS, obese subjects were 1.51 times more likely to reach EDSS score 3 than normal-weight subjects.
Obese subjects whose BMI level didn’t change over time were 1.70 times more likely than the nonobese to develop physical worsening as measured by an increased Multiple Sclerosis Impact Scale physical score of 7.5 points or more, and they were 1.36 times more likely to have psychological worsening as measured by increased MSIS-28 psychological score of 7.5 points or more.
Also, among subjects whose BMI didn’t change over time, the likelihood of cognitive disability worsening was 1.47 times higher among obese participants versus nonobese participants. Worsening was defined as an increased Symbol Digit Modalities Test score of 8 points or more.
The level of excess cognitive decline “will affect people significantly,” Dr. Alfredsson said.
While obesity can counterintuitively provide a protective effect in some diseases, he said there’s no sign of such an effect in the subjects.
As for limitations, Dr. Alfredsson noted in his presentation that BMI data is self-reported, and it’s possible that the researchers didn’t adjust their statistics to reflect important confounders.
A 2023 German study of outcomes in MS patients with obesity came to similar conclusions. It tracked 1,066 subjects for up to 6 years and found that “median time to reach EDSS 3 was 0.99 years for patients with BMI of 30 or higher and 1.46 years for nonobese patients. Risk to reach EDSS 3 over 6 years was significantly increased in patients with BMI of at least 30, compared with patients with BMI less than 30 after adjustment for sex, age, smoking (HR, 1.87; 95% CI, 1.3-2.6; P < .001), and independent of disease-modifying therapies.”
However, the German researchers found no link between obesity and higher levels of relapse, contrast-enhancing MRI lesions, or MRI T2 lesion burden.