The association of smoking and cardiovascular disease in a population with low cholesterol levels: a study of 648,346 men from the Korean national health system prospective cohort study.

BACKGROUND AND PURPOSE: The association of smoking with cardiovascular diseases in populations with low cholesterol levels is unclear and this lack of clarity may have contributed to the very high prevalence of smoking in East Asian men. The effect of smoking on stroke subtypes is particularly unclear. METHODS: We used data from a prospective cohort study of 648,346 Korean men aged 30 to 64 years at their baseline assessment in 1992. RESULTS: Mean (SD) total cholesterol at baseline was 4.9 (1.0) mmol/L and 59% of the men were current smokers. Over the follow-up period of 10 years, 9475 men experienced any type of stroke, 4768 experienced an ischemic stroke, 2380 an intracerebral hemorrhage, 786 a subarachnoid hemorrhage, 3329 men experienced a myocardial infarction, and 269 an aortic aneurysm. Smoking at baseline was associated with marked increases in risk of ischemic stroke (hazard ratio comparing current smokers with never smokers 1.58 [95% CI: 1.49 to 1.68]), subarachnoid hemorrhage (1.91 [1.63 to 2.24]), myocardial infarction (2.01 [1.87 to 2.17]), and aortic aneurysm (1.47 [1.14 to 1.90]) with these effects remaining after adjustment for potential confounding factors and with the first 5 years of events excluded from the analyses. The effect of smoking on these outcomes was the same among men with cholesterol levels below the median value for this population as among those with higher levels. There was no association of smoking with intracerebral hemorrhage. Smoking accounted for 20% of all cardiovascular disease outcomes in this population. CONCLUSIONS: Smoking is a major risk factor for cardiovascular diseases in populations with low cholesterol levels and global interventions are required to halt the emerging tobacco epidemic in low- and middle-income countries.