Passive smoking linked to increased diabetes risk

Passive smoking could increase the risk of developing type 2 diabetes. Picture: John Devlin

A wide-ranging analysis of 88 studies covering nearly six million people had found that both smokers and people breathing in second-hand smoke could see an increased risk of developing the debilitating condition.

Glasgow scientist Professor Naveed Sattar led calls for public health warnings to include diabetes among the illnesses linked to smoking.

The study, which is published today in the Lancet Diabetes and Endocrinology journal, found current smokers face an increased risk of 37 per cent, former smokers by 14 per cent and passive smokers by 22 per cent, compared to those who have never smoked.

The new study estimated nearly an eighth of diabetes cases in men and 2.4 per cent in women – approximately 27·8 million cases – are attributable to smoking worldwide if smoking is causally related to diabetes.

There was also a 54 per cent increased risk of diabetes in new quitters compared to people who have never smoked, which fell to 18 per cent increased risk after five years and 11 per cent increased risk after ten years. Authors Professor Frank Hu, of Harvard University, and Professor An Pan, of Huazhong University of Science and Technology, said: “In view of the high prevalence of smoking in many countries and the increasing burden of diabetes worldwide, reducing tobacco use should be prioritised as a key public health strategy, which could potentially contribute to prevention and control of diabetes.

“Finally, the mechanisms underlying the short-term increased risk of diabetes in recent quitters need to be further explored, since an improved understanding of this effect could contribute to the development of targeted pharmaceutical and lifestyle interventions that could be used to aid smoking cessation and prevent the occurrence of type 2 diabetes.”

The US surgeon general’s report included a section of smoking and diabetes risk for the first time last year and argued for the causal relation between them.

Writing in a linked comment, Prof Sattar, professor of metabolic medicine at Glasgow University, said: “Doctors should mention that, as well as being a risk factor for cardiovascular disease and many cancers, smoking should also be regarded as a risk factor for diabetes – albeit with a small effect relative to, for example, lung cancer.

“Patients who smoke should also be informed that stopping smoking and maintaining long-term abstinence will not only lessen their cardiovascular and cancer risks, but over time, might also lessen their diabetes risk.

“Of course, convincing people to never take up smoking would be even better; in this respect, public health messages should perhaps now include diabetes on the list of smoking-related harms.”

People with diabetes are at increased risk of cardiovascular complications, so smoking is even more harmful, warned Dr Richard Elliott, Diabetes UK research communications manager.

Dr Elliott said: “We know that both smoking and passive smoking are extremely harmful for many reasons and that a huge proportion of people who smoke die as a result of it.

“This study adds to evidence of a link between smoking and increased Type 2 diabetes risk, but does not prove that smoking directly causes Type 2 diabetes.”