Smoking, the most preventable cause of death worldwide, contributes to a host of serious health conditions, including heart disease, cancer, and stroke. A growing number of studies, however, have also found evidence of a connection between smoking and the most common form of diabetes. A meta-analysis published in the December edition of the Journal the American Medical Association (JAMA) found that smokers have an increased risk of developing type 2 diabetes.
A team of researchers from the University of Lausanne in Switzerland reviewed 25 studies, all published between 1992 and 2006, involving the connection between smoking and diabetes. A total of 1.2 million participants were included, none of whom had diabetes before the research began, and the studies identified 45,844 new cases of diabetes. The researchers found that smokers had a 44% greater chance of developing diabetes than nonsmokers, and that risk varied depending on the number of cigarettes smoked each day. Heavy smokers, those who smoked more than 20 cigarettes a day, had a 61% greater risk when compared to lighter smokers, whose increased risk was only 29%. When compared with active smokers, former smokers had an increased risk of 23%.
Scientists believe that smoking may cause insulin resistance, a condition where the body loses its ability to generate a normal insulin response from muscle, fat, and liver cells. Insulin resistance often develops into type 2 diabetes. However, the link between smoking and diabetes could be explained by other factors. Smokers may also engage in other unhealthy behaviors known to contribute to the development of diabetes, such as a sedentary lifestyle, poor diet, and weight gain. The Swiss researchers emphasize the need for future studies to examine these and other possible confounding factors. They believe that the association between smoking and diabetes has been proven, and scientists should now try to determine if that relationship is causal.
In an editorial which also appears in this month's edition of JAMA, Dr. Eric Ding and Dr. Frank Hu, both of the Harvard School of Medical Health, write of the implications this study should have for healthcare providers. They believe physicians should warn smokers of their increased risk for diabetes and monitor smokers for signs of diabetes. Diabetics already have an increased chance of developing high blood pressure and heart disease, and smoking adds to these individuals' risk for premature death. Increased awareness of how smoking may contribute to diabetes may motivate some smokers to quit, and this will hopefully reduce the number of people developing type 2 diabetes.
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