Cigarette smoking and glycaemia: the EPIC-Norfolk Study

Background Previous prospective studies have suggested that cigarette smoki ng may be associated with an increased risk of type 2 diabetes, but the pos sibility of confounding, particularly by dietary factors has not been fully examined. Methods Cross-sectional analysis of the association between cigarette smoki ng and HbA(1C), a marker of long-term glucose homeostasis in 2704 men and 3 385 women, aged 45-74 years who were recruited to a population-based study of diet and chronic disease. Results Twelve per cent of men and 11% of women reported being current smok ers. Mean HbA(1C) was lowest in never smokers, intermediate in former smoke rs and highest in current smokers. There was a dose-response relationship b etween HbA(1C) levels and number of cigarettes smoked per day and a positiv e association with total smoking exposure as measured by pack-years. The un adjusted increase in HbA(1C) for 20 pack-years of smoking was 0.12% (95% CI :0.09-0.16) in men and 0.12% (95% CI:0.08-0.17) in women. After adjustment for possible confounders including dietary variables, the values were 0.08% (95% CI:0.040.12) and 0.07% (95% CI:0.02-0.12) for men and women, respecti vely. Mean HbA(1C) was inversely related to time since quitting smoking to men. Conclusions These results add support to the hypothesis that smoking has lo ng-term effects on glucose homeostasis, an association that cannot be expla ined by confounding by dietary factors as measured in this study.