People who smoke — versus those who don't — have an increased risk of developing Type 2 diabetes, suggests a new review of multiple studies.

The review of 25 studies published between 1992 and 2006 appears in the Dec. 12 issue of the Journal of The American Medical Association. The total number of study participants was 1.2 million and the number of diabetes cases found during the study period was 45,844.

Researchers theorize that smoking may "lead to insulin resistance or inadequate compensatory insulin secretion responses."
(CBC)

The review found that people who smoke have a 44 per cent increased risk of developing Type 2 diabetes over those who don't smoke. And the amount a person smokes also plays a part. Those participants who smoked heavily (20 or more cigarettes per day) had an increased risk of 61 per cent; light smokers had a 29 per cent increased risk and former smokers had a 23 per cent increased risk.

"Heavy smokers are more likely to get diabetes over time than are lighter smokers … who are in turn are more likely to get diabetes than non-smokers," Calgary-based Dr. William Ghali, one of the review authors, told CBC News Tuesday.

While researchers are hesitant to directly link smoking to the onset of diabetes, they theorize that smoking may "lead to insulin resistance or inadequate compensatory insulin secretion responses," according to the authors, primarily from the University of Lausanne in Switzerland. Insulin resistance means the body is less able to both store and process glucose, causing blood glucose levels to rise and leading to the development of Type 2 diabetes.

"Conversely, there are also possible non-causal explanations for this association. Smoking is often associated with other unhealthy behaviors that favor weight gain and/or diabetes, such as lack of physical activity, poor fruit and vegetable intake, and high alcohol intake," researchers said.

The authors urge further studies to determine the roles obesity, lack of exercise, diet and stress have on the development of diabetes.

More than two million Canadians live with diabetes, a costly problem for the health-care system. Its complications cost the Canadian health system more than 13 billion dollars a year. And it's estimated diabetes will cost close to 20 billion dollars by 2020, according to the Canadian Diabetes Association.

Halifax diabetes expert, Dr. Ehud Ur, hopes this latest research dispels some myths.

"Apart from causing heart disease and cancers, [which] we've known for a long time, we now know [smoking] accelerates progression to diabetes and so the argument that you can keep your weight down and prevent diabetes by smoking cigarettes is clearly false," he said.