Background:
Smoking has long been positively associated with the development and progression of coronary heart disease. However, longitudinal cohort studies evaluating smoking habits among cardiac patients as well as the role of socio-demographic factors determining such behaviours are scarce and have been focused on primary care practice. Thus the aim of the present work was to examine the association of active smoking and behaviours and exposure to second-hand smoke, with the 10-year Acute Coronary Syndrome (ACS) prognosis, among cardiovascular patients.

Methods:
From October 2003 to September 2004, a sample of six Greek hospitals was selected and almost allconsecutive 2172 ACS patients were enrolled. In 2013–14, the 10-year follow-up was performed in 1918 participants (11 % loss to follow-up). Smoking habits at the time of entry to the study, as well as during the follow-up period were studied using a standard questionnaire.

Results:
Patients who had >60 pack-years of smoking had 57.8 % higher ACS mortality and 24.6 % higher risk for any ACS event. Nested model, adjusted only for age and sex, revealed that for every 30 pack-years of smoking increase, the associated ACS risk increased by 13 % (95 % CI 1.03, 1.30, p = 0.001). When further adjusted analysis, including several potential confounders, was applied the tested relationship was still significant (95 %CI 1.03, 1.30, p = 0.09). Accordingly, the risk for fatal ACS events increased by 8 % for every 30 pack-years of smoking increase (95 % CI 1.03, 1.63, p = 0.06). Moreover, 52 % of the patients reported being exposed to secondhand smoke and when further adjustments were made, it was revealed that they had 33 % (95 % CI 1.12, 1.60, p = 0.01) higher risk of having recurrent ACS events.

Conclusions:
Active smoking and second-hand smoke among cardiac patients still represent a substantial clinical burden. Thus, smoking cessation policies should be incorporated into the long-term therapeutic management.