Cigarette smoking is a major risk factor for atherosclerosis (narrowing or blockage of arteries due to fat deposits), which often leads to heart attacks and stroke. However, having high cholesterol levels, high blood pressure, and being overweight are also well-known risk factors. One might therefore expect that having low levels of cholesterol and being relatively thin would counterbalance the ill effects of smoking. In South Korea, where the men have normal or low cholesterol levels, are mostly lean, and smoke a lot, heart attacks are increasingly common. A recent study from Korea shows that cigarette smoking is an independent risk factor for heart attacks and stroke - in other words, it is not canceled out by having a low cholesterol level.

Over 100,000 Korean men aged 35-59, who were required to have a full medical exam every two years, were evaluated. Their smoking habits were obtained by questionnaire, along with information on alcohol intake. Information on illnesses and deaths were obtained from hospital discharge records and death certificates over a 6-year period.

The average age of those enrolled was 45 years at the start of the 6-year period; 58% were current smokers, and 21% were ex-smokers. Sixty percent had a normal cholesterol level and 30% had a borderline raised level (200-239 mg/dL, or 5.17-6.18 mmol/L).

After 6 years, almost 3% of the 100,000 men had had a cardiovascular "event" - there were over 1,000 heart attacks, and about 1,350 strokes. Analysis showed that smokers were 2.2 times as likely to have a heart attack than non-smokers. Significantly, ex-smokers were 2.1 times as likely to suffer a heart attack. Smokers were 1.6-times as likely to have a stroke as non-smokers, while for ex-smokers the likelihood was 1.3 times. The number of cigarettes smoked daily and the number of years smoked significantly worsened the likely risk for both heart attacks and stroke.

As with Western people, hypertension, raised total cholesterol and diabetes were associated with significantly raised risk for all atherosclerotic events. Nevertheless, smoking carried an increased risk of heart attack and stroke whatever the cholesterol level. The greatest risk from smoking (3.3 times the risk of non-=smokers) was found in the group of people with the lowest cholesterol levels.

The clear implications of this study - i.e. that smoking is a risk factor for heart attack and stroke independent of the cholesterol level - may not get the attention they deserve because they were obtained in an Asian population. Ethnic differences in nutrition, environmental hazards and lifestyles may lead people to write off the findings as irrelevant for Western countries. This would be a serious mistake. Smoking remains one of the most important risk factors for ill health, not just because of this association with atherosclerotic conditions, but also because of its other effects - causing lung cancer, aggravating osteoporosis, and being largely responsible for chronic bronchitis and emphysema, and degenerative eye diseases.