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Smokers Have High Risk for Type 2 Diabetes
Smokers have a significantly higher risk for developing type 2 diabetes according to the analysis of numerous international studies. And the more one smokes, the higher the risk. Type 2 diabetes can lead to complications such as heart disease and kidney failure.
The review of 25 studies included 1.2 million people from around the world and tracked some of them for as long as 30 years.
"What we found is that smoking is indeed associated with the later development of diabetes, and it's a remarkably consistent association in the combined results of these 25 studies," said co-principal author Dr. William Ghali, a professor of medicine and community health sciences at the University of Calgary.
The strongest link between diabetes and smoking is for heavy smokers (a pack of cigarettes or more per day). These users had an increased risk of 61% compared with non-smokers. Lighter smokers (less than a pack a day) had a 29% higher risk and former smokers a 23% higher risk.
Even though these studies shows a strong relationship between smoking and diabetes, they do not prove tobacco is directly responsible for the condition. It would take clinical trials comparing smokers and non-smokers matched for age, sex and other factors.
"Smoking is often associated with other unhealthy behaviours that can lead to diabetes, including physical inactivity, poor diet and high alcohol consumption," Ghali said. "It might not be the smoking, per se, but those other mediating factors that are related to smoking and separately related to diabetes."
However, the relationship is so strong that "it may be that smoking is associated independently . . . and (is) more likely to be a causal link," Ghali speculated.
"In all of the studies, the smoking preceded the development of diabetes."
There is also a biological basis for blaming tobacco as a possible cause to type 2 diabetes. Smoking is associated with cancer of the pancreas, the organ that produces insulin. Some research suggests smoking leads to insulin resistance or inadequate insulin secretion. Both of these are key factors in this type of diabetes.
"In trying to put together a case for saying this is causal, it kind of catches the attention that there is obviously some toxicity to that particular organ," Ghali said. "So it does make it compelling to say, well perhaps that's yet another argument that there are effects on insulin secretion - and insulin secretion occurs in the pancreas."
"So there's lots of reasons not to smoke."
Dr. Bernard Zinman, a diabetes expert at Mount Sinai Hospital in Toronto, said "Right now, we're clearly in the midst of an epidemic globally of diabetes. There's no question that there are many factors that are contributing to the diabetes epidemic, the most important one of which appears to be the obesity epidemic and the fact that we're far more sedentary."
"So here we see there's another risk factor - and the risk factor is a history of smoking."
"So in the context of healthy behaviours and healthy lifestyles, this is a very, very important observation, particularly in some countries where there isn't that major effort to quit smoking," said Zinman, pointing to Asia, Japan and China as examples where smoking rates remain high.
Risk reduction for type 2 diabetes is achievable through avoiding smoking and modification of lifestyle through healthy weight control, regular physical activity, moderate alcohol consumption and proper diet.