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.
These findings were reported in the study, “Estimated and projected burden of multiple sclerosis attributable to smoking and childhood and adolescent high body-mass index: a comparative risk assessment,” published in the International Journal of Epidemiology.
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.
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.
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