Background Cigarette smoking remains the leading avoidable cause of disease burden worldwide, and observational studies have linked various smoking behaviors (active and passive smoking and smoking cessation) with risk of type 2 diabetes. We did a meta-analysis of prospective studies assessing the relation of various smoking behaviors and diabetes risk. Methods We systematically searched MEDLINE and EMBASE databases (up to 3 May 2015) with manual searches of the references of retrieved publications and relevant reviews. We included prospective studies that reported risk of type 2 diabetes by baseline smoking status. Relative risks (RRs) and 95% confidence intervals (CIs) were pooled using random-effects models, and subgroup analyses were performed by participant and study characteristics. Findings The search yielded 88 prospective studies with nearly 6 million participants and 295446 incident cases. Compared with never smoking, the pooled RR (95% CI) of type 2 diabetes was 1·37 (1·33-1·42) for current smoking (84 studies), 1·14 (1·10-1·18) for former smoking (47 studies), and 1·22 (1·10-1·35) for passive smoking (7 studies). The associations persisted in all subgroups, and a dose-response relation was found for current smoking and diabetes risk: the RRs (95% CIs) were 1·21 (1·10-1·33), 1·34 (1·27-1·41) and 1·57 (1·47-1·66) for light, moderate, and heavy smokers, respectively, compared with never smokers. We estimated that 10·3% in men and 2·2% in women of type 2 diabetes cases (approximately 25 million) were attributable to cigarette smoking worldwide if smoking is causally related to diabetes. Compared to never smokers, the pooled RR (95% CI) from 10 studies was 1·54 (1·36-1·74) in new quitters (<5 years), and 1·11 (1·02-1·20) in long-term quitters (≥10 years). Interpretation Active and passive smoking are associated with significantly increased risks of type 2 diabetes. The risk of diabetes is elevated in new quitters, but decreases substantially as the time since quitting increases.

Background Prevalence of smoking in diabetic patients remains high, and reliable quantification of the excess mortality and morbidity risks associated with smoking is important for diabetes management. We performed a systematic review and meta-analysis of prospective cohort studies to evaluate the relation of active smoking with risk of total mortality and cardiovascular events among diabetic patients. Methods and Results We searched MEDLINE and EMBASE databases through May 2015, and multivariate-adjusted relative risks (RRs) were pooled using random-effects models. A total of 89 cohort studies were included. The pooled adjusted RR (95% confidence interval [CI]) associated with smoking was 1.55 (1.46–1.64) for total mortality (48 studies with 1,132,700 participants and 109,966 deaths), and 1.49 (1.29–1.71) for cardiovascular mortality (13 studies with 37,550 participants and 3,163 deaths). The pooled RR (95% CI) was 1.44 (1.34–1.54) for total cardiovascular disease (CVD; 16 studies), 1.51 (1.41–1.62) for coronary heart disease (CHD; 21 studies), 1.54 (1.41–1.69) for stroke (15 studies), 2.15 (1.62–2.85) for peripheral arterial disease (3 studies), and 1.43 (1.19–1.72) for heart failure (4 studies). Compared to never smokers, former smokers were at a moderately elevated risk of total mortality (1.19; 1.11–1.28), cardiovascular mortality (1.15; 1.00–1.32), CVD (1.09; 1.05–1.13) and CHD (1.14; 1.00–1.30), but not for stroke (1.04; 0.87–1.23). Conclusions Active smoking is associated with significantly increased risks of total mortality and cardiovascular events among diabetic patients, while smoking cessation was associated with reduced risks compared to current smoking. The findings provide strong evidence for the recommendation of quitting smoking among diabetic patients.

A 10-year longitudinal population-based study, entitled the Isfahan Cohort Study (ICS) is being conducted. The ICS commenced in 2001, recruiting individuals aged 35 þ living in urban and rural areas of three counties in central Iran, to determine the individual and combined impact of various risk factors on the incidence of cardiovascular events. After 24379 person-years of follow-up with a median follow-up of 4.8 years, we documented 219 incident cases of ischemic heart disease (IHD) (125 in men and 94 in women) and 57 incident cases of stroke (28 in men and 29 in women). The absolute risk of IHD was 8.9 (7.8-10.2) per 1000 person-years for all participants, 10.6 (8.8-12.5) per 1000 person-years for men and 7.4 (6.0-9.0) per 1000 person-years for women. The respective risk of ischemic stroke was 2.3 (1.7-3.0), 2.3 (1.6-3.3) and 2.3 (1.5-3.2) per 1000 person-years. The risk of IHD was approximately 3.5-fold higher in the presence of hypertension, followed by diabetes mellitus and hypercholesterolemia with near 2.5-and twofold higher risk, respectively. This cohort provides confirmatory evidence of the ethnic differences in the magnitude of the impact of various risk factors on cardiovascular events. The differences may be due to varying absolute risk levels among populations and the existing ethnic disparities for using western risk equations to local requirements.