Smoking may be a risk factor for developing diabetes. But could breathing in someone else's smoke also put you at risk? Yes, according to a multicenter US study.


Researchers tracked 4,572 men and women in four American cities for 15 years. They divided participants into four categories—current smokers...previous smokers...never smokers with exposure to secondhand smoke...and never smokers without such exposure. Not surprisingly, at the 15-year follow-up, smokers had the highest incidence of glucose intolerance—impaired fasting glucose or diabetes—at 21.8%. However, second place went to the never smokers who were exposed to passive smoke—17.2%...followed by the previous smokers (14.4%)... and then never smokers who were not exposed to secondhand smoke (11.5%).


That sounds pretty convincing. Endocrinologist Melissa D. Katz, MD, assistant professor of medicine in the division of endocrinology, diabetes and metabolism at Weill Cornell Medical College in New York City, says it is an interesting study—as far as it goes. Yet, in spite of its 15-year duration, the study has serious limitations, which the authors also acknowledge. It was partly based on self-reporting—participants relay the information about their habits—and this is always problematic, says Dr. Katz. People don't often keep good records and they also tend to make themselves look better by claiming they eat better and exercise more and smoke less than they do. There is really no way ro know what participants actually did. And of course, as Dr. Katz points out, people exposed to secondhand smoke are likely to live with smokers, who often don't have the healthiest lifestyle.

Likely cause of secondhand smoke increasing risk: The study authors speculate that because secondhand smoke “is produced at different temperatures and different reducing conditions," toxins can be more concentrated in passive smoke than smoke that goes straight into the lungs. It's possible, the researchers say, that smoking is linked to diabetes because toxins in tobacco smoke can affect the pancreas, the organ that produces insulin. Nonetheless, she adds, the study does show once again the critical role lifestyle plays in helping prevent or control diabetes.

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