Smokers have the potentials of developing type 2 diabetes on HWN RESEARCH

The link between passive smoking and diabetes raises a new concern, given a recent suggestion that more than 30% of worldwide nonsmokers are exposed to secondhand tobacco smoke, contributing to about 1% of global total mortality and 0.7% of disease burden.

Among current active smokers, the increased risk of developing type 2 diabetes is estimated to be 21% for light smokers, 34% for moderate smokers and 57% for heavy smokers, compared with never-smokers.

If smoking does contribute to diabetes, the authors estimate that 11.7% of global diabetes cases in men and 2.4% in women - approximately 27.8 million cases in total - are attributable to active cigarette smoking.
Increased risk of diabetes at the time of quitting

Interestingly, there was a 54% increased risk of diabetes in new quitters - those who quit less than 5 years ago - compared with those who had never smoked. This fell to an 18% increased risk after 5 years and 11% increased risk in long-term quitters - those who quit more than 10 years ago.

Although former smokers appear to be at greater risk than those who have never smoked, the increased risk in the long run is much lower in quitters than it is in those who are still smoking, making avoidance of diabetes in the long term a valid argument for quitting smoking.

Could the higher risk of type 2 diabetes after giving up smoking be attributable to the weight increase that typically occurs at that stage, of 4-5 kg on average in the first year? Type 2 diabetes tends to be associated with high BMI, but the researchers found that even with adjustments for baseline body mass index (BMI), the increased diabetes risk remained.

Moreover, one study observed that male new quitters who gained less than 3 kg weight during the first 5 years after cessation were more likely to develop diabetes on average, whereas those who gained 3 kg or more did not, supporting the view that this weight gain in itself is not to blame.
In a related comment, Naveed Sattar, of the University of Glasgow in the UK, and colleagues refer to genetic studies proposing that although smoking reduces BMI, it might "preferentially promote central adiposity, as shown by a greater waist circumference for a given BMI."

This suggests that the common belief that smoking helps keep weight down might be misleading - it may reduce BMI, but not necessarily fat or waistlines.

One limitation considered was the fact that smoking is often related to other unhealthy lifestyle factors, such as poor diet, excessive alcohol use and physical inactivity, which could confound the results. However, no substantial differences were noted when adjustments were made for these factors.

The benefits of quitting smoking, such as reducing the risk of cardiovascular disease, are well documented, in both the short and long term, including in patients with diabetes.

 While Sattar cautions that the link is not "definitive," the researchers believe there is a strong case for associating type 2 diabetes with smoking and call for further research in the field. They also emphasize the importance of adopting and enforcing smoke-free legislation to reduce the number of people exposed to secondhand smoke.

If the association between smoking and risk of type 2 diabetes is causal, public health efforts to reduce smoking could have a substantial effect on the worldwide burden of type 2 diabetes.