Background: Smoking is a major risk factor for heart disease. Over the past decade, the prevalence of smoking and the number of cigarettes smoked per day have decreased in Canada. Using a contemporary cohort of Canadian men and women, this study measured associations between smoking, smoking cessation and heart disease.
Methods: The study is based on nine cycles of data (1994/1995 through 2010/2011) from the National Population Health Survey, which collected information on smoking status every two years. The study sample consists of 4,712 men and 5,715 women aged 25 or older and free from heart disease in 1994/1995. Heart disease was determined by self-report of diagnosis, medication for, or death from heart disease. Relative risks of incident heart disease were compared among current daily smokers, former daily smokers, and those who never smoked daily.
Results: Compared with those who had never smoked daily, current daily smokers had a 60% higher risk of incident heart disease during the follow-up period. The risks were lower among current daily smokers who consumed fewer cigarettes. Although smoking cessation was associated with a lower risk of heart disease, 20 or more years of continuous cessation were required for the risk to approach that of people who never smoked daily.
Interpretation: Smoking cessation and cutting down the number of cigarettes smoked per day reduce the risk of heart disease.
Keywords: cohort study; longitudinal studies; relative risks.