Cigarette smokers may be nearly three times more likely to develop type 2 diabetes.

Researchers followed a group of more than 900 adults and found smokers were 2.7 times more likely to develop type 2 diabetes in the next five years than people who had never smoked.

"We've known for years that smoking causes lung cancer and seriously raises the risk for heart disease," researcher Capri Foy, PhD, of Wake Forest University School of Medicine's Department of Public Health Sciences, says in a news release. "These findings suggest another poor health outcome associated with smoking."

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Smoking Linked to Type 2 Diabetes

In the study researchers looked at 906 middle-aged adults and calculated how many of them got type 2 diabetes in the following five years.

The results showed that 25 percent of current smokers developed type 2 diabetes compared with 14 percent of people who never smoked. This held true even after adjusting for other potential risk factors for diabetes, such as age, being overweight, and waist size.

Researchers say the findings suggest that aside from its other proven health risks, cigarette smoking may by itself increase the chance of developing type 2 diabetes.

The study appears in the October issue of Diabetes Care.

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"There are several possible mechanisms by which smoking may increase a person's risk for developing diabetes," says Foy. "For instance, higher levels of abdominal fat are associated with increased risk of diabetes, and some studies have shown that smokers tend to have more abdominal fat compared to people who have never smoked.”

"Also, many studies have found that increased blood glucose levels, increased insulin levels, and increased blood pressure are all associated with increased risk of diabetes, and active bouts of smoking can produce increases in all three of these factors," says Foy. "What's more, cigarettes contain many poisonous substances along with nicotine, such as cadmium, which has been shown to be associated with diabetes.”

Researchers say more studies are now needed to determine precisely how cigarette smoking affects the risk of type 2 diabetes.

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By Jennifer Warner, reviewed by Michael W. Smith, MD

SOURCES: Foy, C. Diabetes Care, October 2005; vol 28: pp 2501-2507. News release, American Diabetes Association.