Introduction

More and more women smoke today, and many, if not most of them, are well aware of the risks involved. They'll say, "I only smoke 2-3 a day" or, "I don't inhale", and reason that they are not at increased risk. But this isn't really the case, as a new study from Denmark has shown.

What was done

The Copenhagen City heart Study followed over 14,000 people over a 20-year period, looking for possible links between their smoking habits and whether they had a heart attack (myocardial infarction or MI), or died from some other cause. Only people over 30 were included, to make sure that smoking habits were well established at the start of the study. People with previous heart symptoms or those with inadequate information on their heart risk factors were excluded.

Questionnaires and lab tests were done at baseline to determine existing heart risk factors. These covered height & weight (to give the body mass index, or BMI), educational level, household income, alcohol intake, physical activity, family history of diabetes or MI, blood pressure, and blood cholesterol levels.

Smoking status was recorded as never-smoked, former-smoker, or current smoker. Current smokers gave the amount and type of tobacco smoked, and whether they inhaled or not. For the purpose of analysis across the board one cigarette was equated to 1 gram of tobacco, a cheroot to 3 grams, and a cigar to 5 grams.

The results

Over 2,000 of the original volunteers were excluded because of they were under 30, had a history of heart disease, or were missing information on risk factors. This left over 6,500 women and 5,500 men in the study.

During the 20-odd years, 7.3% of the women and 15.5% of the men had an MI. Of these, 40% died. Deaths from all causes were 35% in women and 51% in men.

More men smoked than women (70% vs. 58%), they smoked more (measured in grams of tobacco per day), and more of the men inhaled (77% vs. 70%). Women smoked cigarettes more than men (81% vs. 57%), although both sexes favored cheroots (14% and 17%, respectively).

After making allowances for their recorded heart risk factors, it was clear that the more the people in the study smoked (grams of tobacco a day), the more likely they were to have an MI or die from some other cause. This was the case in both men and women, and in women whether they inhaled or not.

The investigators wanted to find out the lowest level of smoking that significantly increased the risks.

In women, 6 or more cigarettes ¹ a day for non-inhalers and 3 or more cigarettes a day for inhalers significantly increased - roughly doubled - the risk for having an MI or dying from any cause. In men, the level was 6 or more cigarettes a day for inhalers; male non-inhalers were not at increased risk.

Comment

This study shows that smoking as few as 3 cigarettes a day for women (or 3 grams of tobacco in another form) or 6 cigarettes a day for men significantly increases the risk of having an MI or dying from some other cause. These risks were roughly 1½ times greater in women than in men. The findings together with similar results from other studies, reinforces the fallacy of "cutting down" as an escape from the dangers of smoking.

Inhaling, or not inhaling, is not usually considered separately in studies of the effects of smoking. In this study, non-inhaling women who smoked clearly shared the risk, though at a lesser level than inhalers.

Why should women be at a greater disadvantage than men when it comes to smoking? One explanation may be that smoking has an anti-estrogen effect, thus robbing them of a 'protective' effect that estrogens are supposed to have on the development of atherosclerosis, a forerunner of coronary artery disease and MI.

It must be remembered that this study was done in Demark, where lifestyles and smoking habits are not necessarily the same as in other countries. For instance, the cardiovascular risk factors showed that men had a better risk profile with regard to total cholesterol, alcohol consumption, physical activity, income and education, while women had better triglyceride, blood pressure, BMI and diabetic risk factors. This picture would probably not be found in many countries. And cheroots are not widely smoked in the USA, for instance. Nevertheless, the findings emphasize that no female smoker is safe -- not even those who only smoke 3 or 4 cigarettes a day, or don't inhale!