How smoking can give you diabetes

Current smokers and people regularly exposed to second-hand smoke have a significantly increased risk of developing type two diabetes, compared with those who have never smoked, according to a new study.

Researchers from Harvard University's School of Public Health, Huazhong University of Science and Technology in China, and National University of Singapore estimated that 11.7 per cent of cases of type two diabetes in men and 2.4 per cent in women (27.8 million cases in total worldwide) might be attributable to active smoking. They also found the risk decreases as time elapses after smokers quit. "Cigarette smoking should be considered a key modifiable risk factor for diabetes. Public health efforts to reduce smoking will have a substantial impact on the global burden of type two diabetes," said co-author Frank Hu, professor at the Harvard T H Chan School of Public Health.

While the evidence pointing to smoking as a risk factor for cancer, respiratory diseases, and cardiovascular disease is overwhelming, corroboration of a link between smoking and type two diabetes risk has been slower to build. In the study, researchers conducted a meta-analysis of 88 previous studies on the association between smoking and type two diabetes risk, looking at health data from nearly six million study participants.

They found that when compared with people who never smoked, current smoking increased the risk of type two diabetes by 37 per cent; former smoking by 14 per cent; and passive smoking (breathing in second-hand smoke) by 22 per cent. They also found a 54 per cent increased risk of type two diabetes in people who quit smoking less than five years ago, which fell to 18 per cent increased risk after five years and 11 per cent increased risk more than 10 years after quitting.

The increased risk of developing type two diabetes was 21 per cent, 34 per cent, and 57 per cent for light, moderate, and heavy smokers, respectively, compared with those who never smoked."

Despite the global efforts to combat the tobacco epidemic, cigarette use remains the leading cause of mortality and morbidity across the world," said first author An Pan, professor at the Huazhong University of Science and Technology. The study was published in The Lancet Diabetes and Endocrinology Journal.