Tobacco Smoking and Incident Hospitalisation for Cardiovascular Disease in the Australian 45 and Up Study
METHODS: Self-reported data from 170,373 individuals with no history of CVD joining a large-scale Australian cohort study (The 45 and Up Study) by completing a questionnaire distributed from 2006-2008 were linked prospectively to hospitalisation and mortality data. Hazard ratios (HRs) for incident hospitalisation for specific CVD diagnoses among current, past and never smokers were estimated separately for men and women using Cox regression, adjusting for age, region of residence, alcohol consumption, income, education, physical activity and body-mass-index.
RESULTS: In the cohort, 8% of participants were current smokers and 33% were past smokers. Over a mean follow up time of 3.7 years there were 10,868 incident CVD admissions over 625,767 person-years; including 3,479 for ischaemic heart disease (IHD); 1581 for stroke; 480 for peripheral vascular disease (PVD); and 421 for heart failure. Among men, the hazard ratios (HR, 95%CI) for hospitalisation during the follow up period in current versus never smokers were: 1.65 (1.43-1.91) for IHD; 2.01 (1.20-3.35) for heart failure; 6.77 (4.80-9.55) for PVD; and 1.76 (1.36-2.21) for stroke. Corresponding HR (95%CI) for women were similar: 1.78 (1.45-2.18); 1.93 (1.00-3.74); 5.32 (3.37-8.41); and 1.52 (1.13-2.05). Among current smokers, the adjusted HR of hospitalisation for these outcomes increased significantly with increasing number of cigarettes smoked per day. Cessation of smoking was associated with substantially lower risks than continuing smoking, with greater reductions the younger the age at cessation.
CONCLUSIONS: The risks of different types of CVD are elevated in current smokers, to a similar extent in men and women, with greater smoking-associated relative risks of PVD than of stroke, IHD or heart failure. Cessation of smoking substantially reduces the risk of these CVD types.