Interpretation and commentary
Could obesity be causing worse outcomes? The new study doesn’t provide insight into cause and effect. However, obesity may speed up progression via low-grade inflammation, Dr. Alfredsson said.
What can clinicians do with the information from the study? If patients are obese, it can be a good idea to more carefully monitor them and use reliable tools to improve their progression, Dr. Alfredsson said.
In an interview, Michael D. Kornberg, MD, PhD, an assistant professor of neurology at Johns Hopkins University, Baltimore, who was not involved with the study, agreed with Dr. Alfredsson that other research has linked obesity early in life to higher rates of MS. He added that “a number of studies have shown that comorbidities in general are usually associated with a higher rate of disability.”
Dr. Kornberg said the new research is important, and he noted that it has a “robust” cohort because of its larger size.
Could patients with MS reverse the risk of progression and other poor outcomes by losing weight? “It’s hard to say,” Dr. Kornberg said. “We have to be cautious when we assume causation. There’s a plausible rationale that obesity might worsen progression in MS, but it could just be a marker of some other factor that reflects a different phenotype of MS.”
He doesn’t think it’s likely that weight loss would “dramatically reverse the biology of MS,” but he said reversing the obesity epidemic would still be a good thing. An interventional study could examine the effects of weight-loss intervention on disability measures, he said, “and that’s the next step.”
Also contacted for commentary, Adil Harroud, MD, a neurologist at McGill University who studies obesity in MS, said research suggests that “obesity seems to exacerbate MS disability. While some studies show no effect, the majority indicate a detrimental impact.”
However, “the effect of obesity on MS progression remains unclear. Animal studies suggest that shifts in immune cell subsets and functions may play a role, but the relevance to humans is yet to be determined,” he said.
Dr. Harroud, who did not take part in the new study, said it’s “one of the largest examining the impact of obesity on MS disability.” He added that “the cohort was relatively early in their disease course, suggesting that obesity impacts even the early stages of MS. This underscores the importance of obesity as a modifiable risk factor for disability accumulation.”
As for why obesity affects MS, he said one theory is that obesity plays a role through its impact on vitamin D levels. “However, using a genetic approach, we have demonstrated that, at least for MS risk, the effect of obesity is independent of vitamin D. This is also likely true for MS progression, as recent trials of vitamin D supplementation have not shown a meaningful impact on MS outcomes.”
According to Dr. Harroud, “other theories suggest that obesity leads to a pro-inflammatory immune shift. Additionally, it has been proposed that obesity may influence the response to disease-modifying therapy by reducing drug bioavailability, potentially necessitating weight-based dosing for some therapies.”
Dr. Alfredsson reported receiving grants from the Swedish Research Council, the Swedish Research Council for Health Working Life and Welfare, and the Swedish Brain Foundation and personal fees from Teva and Biogene Idec. Some of the other study authors reported various disclosures. Dr. Kornberg and Dr. Harroud reported no relevant disclosures.
This article was updated 10/20/23.