Background: Few earlier studies have analysed smoking as a risk factor for myocardial infarction (MI) or stroke in type 2 diabetic patients.
Design and methods: A longitudinal study involved 13 087 female and male patients with type 2 diabetes from the Swedish National Diabetes Register with no previous MI or stroke at baseline, aged 30-74 years, and with data available for all analysed variables, followed up for mean 5.7 years.
Results: Adjusted hazard ratios (HRs) for smoking and first-incident fatal/nonfatal MI, stroke and total mortality were 1.7 [95% confidence interval (CI): 1.4-2.0; P<0.001], 1.3 (95% CI: 1.1-1.6; P = 0.006) and 1.8 (95% CI: 1.5-2.2; P<0.001), respectively, by Cox regression analysis, adjusted for age, sex, diabetes duration, hypoglycaemic treatment, haemoglobin A1c, blood pressure, body mass index, microalbuminuria, antihypertensive and lipid-lowering drugs. Adjusted HR was higher for fatal MI, 2.1 (95% CI: 1.7-2.7; P<0.001), than for nonfatal MI, 1.4 (95% CI: 1.2-1.7; P<0.001). The highest HRs were observed in more frequently smoking (22%), middle-aged patients (age <60 years) for fatal/nonfatal MI, 2.3 (95% CI: 1.8-3.1; P<0.001) and for total mortality, 2.5 (95% CI: 1.6-3.8, P<0.001), whereas lower HRs were observed in older and less smoking patients. With predicted cessation of smoking in patients aged below 60 years, 24% (95% CI: 15-33%) of cases of fatal/nonfatal MI and 24% (11-37%) of cases of total mortality may have been prevented.
Conclusion: The risk for MI and total mortality associated with smoking is high in type 2 diabetes, especially in more frequently smoking, middle-aged patients, and was higher for MI than for stroke, and also higher for fatal than for nonfatal events. Smoking cessation would strongly affect risk reduction.