The number of new cases of multiple sclerosis (MS) possibly due to obesity in childhood and adolescence could rise by 14% in the U.S. over the next 15 years, and by 10% in the U.K., a study reported.
While the worldwide risk of MS linked to obesity in early life is increasing, that associated with smoking seem to be declining.
If truly causal, these observations suggest that efforts to prevent obesity and help people to stop smoking — two environmental risk factors for MS — will lower the rate of this disease’s development on a global scale.
“Our findings highlight the potential to reduce the incidence of MS worldwide with targeted public health strategies,” Ruth Dobson, MD, PhD, a clinical senior lecturer at Queen Mary’s Wolfson Institute of Preventive Medicine, and the study’s lead author of the study, said in a news story.
“It is not only cancer and heart disease that are influenced by smoking and obesity — shifting the focus to diseases with onset in early adulthood, such as MS, may resonate more with younger people whose lifestyle choices will have an impact on their risk of future illness,” Dobson added.
Environmental risk factors are estimated to account for more than half (53.3%) of one’s total risk of MS. According to previous studies, smoking and excessive body weight in early life are such risk factors for MS. In fact, up to 1 in 5 cases is linked to smoking.
However, their exact contribution to MS development can be hard to estimate, as obesity and smoking rates change over time and differ across populations.
Investigators at Queen Mary University of London working with colleagues at Barts Health NHS Trust and the University of Oxford, attempted to estimate the number of new MS cases that could be associated with daily smoking (between the ages of 20–24) and obesity (between ages 5–19) by analyzing data from studies performed in the U.K., U.S., Russia, and Australia.
Analyses considered both risk factors individually and combined, for the years of 2015, 2025, and 2035 in all four countries, when possible.
Results showed that in 2015, both risk factors combined potentially accounted for 14% of MS cases in the U.K., 12% in Russia and Australia, and 11% in the U.S. Over the next 10 years, combined estimates indicated that the proportion of new MS cases associated with these factors will stabilize.
“[T]he combined [contribution] of smoking and high BMI on incident MS is anticipated to remain relatively constant between 2015 and 2025 in combined estimates, largely due to the impact of increasing prevalence of increased BMI being offset by declines in smoking,” the researchers wrote.
When looking at these risk factors individually, investigators found that obesity in early life potentially accounted for 11% of MS cases in the U.S in 2015, while smoking accounted for 10%.
The proportion of MS cases associated with smoking dropped over time in all countries, possibly due to greater smoking cessation efforts worldwide. But the proportion associated with obesity in childhood and adolescence increased, potentially accounting for a maximum of 14% of MS cases in the U.S. by 2035, 11% in Australia, and 10% in the U.K.
Russia was the only country where obesity in early life seemed to be associated with a single-digit number of MS cases, increasing from 4% in 2015 to 6% by 2035.
“According to our modelling, a not insubstantial proportion of incident MS risk could be prevented by eliminating smoking and especially high childhood BMI,” the investigators wrote. “Assuming causality, a substantial proportion of MS incidence could be reduced by addressing lifestyle-related modifiable risk factors.”
These “data indicate the magnitude of the problem and highlight the need to act urgently,” the researchers added. “They inform the MS community of potential gains in MS prevention from joining forces with existing preventive campaigns to tackle the leading drivers of premature morbidity and mortality.”
Further studies are needed to determine the probability of direct causation between MS incidence and smoking or high BMI.
Joana holds a BSc in Biology, a MSc in Evolutionary and Developmental Biology and a PhD in Biomedical Sciences from Universidade de Lisboa, Portugal. Her work has been focused on the impact of non-canonical Wnt signaling in the collective behavior of endothelial cells — cells that made up the lining of blood vessels — found in the umbilical cord of newborns.
Patrícia holds her PhD in Medical Microbiology and Infectious Diseases from the Leiden University Medical Center in Leiden, The Netherlands. She has studied Applied Biology at Universidade do Minho and was a postdoctoral research fellow at Instituto de Medicina Molecular in Lisbon, Portugal. Her work has been focused on molecular genetic traits of infectious agents such as viruses and parasites.
Joana holds a BSc in Biology, a MSc in Evolutionary and Developmental Biology and a PhD in Biomedical Sciences from Universidade de Lisboa, Portugal. Her work has been focused on the impact of non-canonical Wnt signaling in the collective behavior of endothelial cells — cells that made up the lining of blood vessels — found in the umbilical cord of newborns.