Active Smoking and the Risk of Type 2 Diabetes, JAMA, December, 2007
Of the 25 studies included in this analysis, 24 reported a positive association between smoking and diabetes, specifically:
"The pooled adjusted RR was 1.44."An RR (Relative Risk) of 1.44 means that there was a 44% increased risk for developing diabetes among active smokers vs. non-smokers. Among heavy smokers, the risk increased to 61%:
"The risk of diabetes was greater for heavy smokers (≥20 cigarettes/day; RR 1.61) than for lighter smokers (RR 1.29) and lower for former smokers (RR 1.23) compared with active smokers, consistent with a dose-response phenomenon."The link was so consistent that the authors stated there was "no need for further cohort studies to test this hypothesis." They recommended instead "that future studies focus on plausible causal mechanisms or mediating factors such as obesity, lack of physical activity, dietary habits, and stress levels."
One mechanism they noted which has appeared in previous studies is smoking's link to insulin resistance or inadequate insulin secretion - a mechanism which should bear scrutiny in future investigations.