Obesity and smoking are well-known risk factors for heart disease and cancer. What is less well known is that they’re associated with an increased risk of multiple sclerosis (MS).
What Is Already Known
Many studies have looked at the relationship between smoking and MS. The largest of these included more than 590,000 people from around the world. It showed that smokers are around 50 percent more likely to develop MS than non-smokers.Smoking, Obesity, and MS
We found that smoking was responsible for between 10 and 14 percent of the population risk of MS in the United Kingdom, United States, Russia, and Australia in 2015. This is much higher in Russian males (22 percent), reflecting high rates of smoking. By 2025, the population risk attributable to smoking is projected to decrease in all the countries studied to between 7 percent and 12 percent.In the United States, childhood obesity accounted for a higher proportion of 2015 MS risk than smoking. Childhood obesity in the United States in 2005 accounted for an eventual 11 percent of MS risk in 2015. In the United Kingdom, this figure was 8 percent. Worryingly, when the potential impact of 2015 rates of childhood obesity are projected, this will contribute up to 14 percent MS risk in the United States and 10 percent in the United Kingdom in 2035.
Trying to look at the combined effects of smoking and obesity is more complex, as the current evidence doesn’t tell us the amount of overlap between the two factors. The overall effect is likely to remain roughly stable, as the increase in childhood obesity offset reductions in smoking.
While this research can’t tell us how childhood obesity and smoking increase MS risk, it shows that there is an urgent need to address childhood obesity. Increasing rates of childhood obesity mean that any gains in MS prevention caused by reduced levels of smoking will be lost. While cancer and heart disease occur in later adulthood, MS onset in young adulthood may be of greater concern to younger people.
Reducing childhood obesity and smoking is likely to have an important impact on MS incidence. Our work shows the size of the problem and highlights the need to act urgently.
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