Quit smoking or do not start at all, a study shows

Researchers found that smoking only one cigarette a day is more harmful than has been widely assumed. Men having one cigarette a day still carry a 74% higher risk of developing coronary heart disease than never-smokers, while women who smoked one a day had a higher risk: 119% of increasing risk. The substantial elevating risk was also observed in stroke where men and women smoking one cigarette per day had, respectively, 30% and 46% increased risk compared to those who never smoke. These results were obtained after taking into account a range of factors such as age, BMI, cholesterol, and blood pressure.

The study, which just recently published in BMJ, examined a body of evidence from 141 prospective cohort studies contained in 55 scientific articles published between 1946 and May 2015. Involving several million people in total, this study assessed the risk of coronary heart disease and stroke from light smoking (one to five cigarettes/day) using the relation between cigarette and cardiovascular disease.

There is a common belief that reducing cigarette consumption will decrease the harm of smoking proportionately – that smoking one cigarette a day has about one twentieth (5%) of the risk of 20 cigarettes per day, which is true for lung cancer case. However, this study suggests, there is a non-linear relation between the cardiovascular disease (coronary heart disease and stroke) with low cigarette consumption.

Distribution of excess relative risk (proportion of the change in risk) for smoking one or five cigarettes per day in relation to smoking 20 cigarettes per day, not taking into account multiple factors. Horizontal lines show median. (The figure was taken from the original article)

Men smoking one cigarette a day had 53% of the coronary heart disease risk of those smoking 20 cigarettes a day, and 64% of their risk of stroke. Meanwhile, women smoking one cigarette a day had 38% of the coronary heart disease risk and 36% of the stroke risk of women smoking 20 cigarettes a day. These unexpected results were also calculated after considering some other essential factors, such as age, sex, BMI, diabetes history, and physical activity.

This study emphasises the incentives for smokers to entirely quit smoking and, moreover, for non-smokers to not even started smoking any single cigarette a day. Although cutting down cigarettes consumption still has benefits, particularly for risk of cancer, the reduction in cardiovascular disease risk is not massive as smokers might expect. Additionally, smokers quitting smoking will gain substantial health benefits associated with their cardiovascular system soon after stopping.

This study worth a note for healthcare professionals and smokers that there is no safe level of smoking exists for cardiovascular disease. Thus light or social smoking should also be discouraged. Furthermore, smoking cessation programme should aim to help smokers to quit instead of cutting down to significantly avoid most of their risk of the heart disease and stroke, the two most common disorders caused by smoking.

Full article: http://www.bmj.com/content/360/bmj.j5855

Beladenta Amalia (Pre-doctoral researcher)