Secular trends in smoking in relation to prevalent and incident smoking-related disease: A prospective population-based study.

Introduction: We examined changes in smoking habits in the general population according to prevalence and incidence of chronic diseases affected by smoking.

Methods: We included 12283 individuals enrolled from 2003 in the Copenhagen General Population Study and re-examined from 2014. Participants were classified as either healthy or suffering from chronic obstructive pulmonary disease (COPD), asthma, diabetes mellitus, heart disease or stroke.

Results: At entry, smoking prevalence was 15.4% in healthy participants, 29.8% with COPD, 15.8% with asthma, 21.7 % with diabetes mellitus, 17.2 % with ischemic heart disease/heart failure and 18.6% in participants with previous stroke. Smoking prevalence declined during the 10 years of observation. Among healthy subjects who developed one of the above mentioned diseases during follow-up, those who developed COPD had the highest initial smoking prevalence (51.5%). Quit rates were highest in those who developed asthma resulting in smoking prevalence of 8.2% versus 27.7% in COPD. After adjustment for age, smoking severity and genotype previously associated with heavy smoking (CHRNA3 rs1051730 AA), significant predictors of quitting were new diagnosis of ischemic heart disease/heart failure (OR=2.33, 95 % CI: 1.61-3.42), new diagnosis of asthma (OR=1.84, 95% CI: 1.18-2.90) and low number of pack-years.

Conclusions: Individuals with prevalent smoking related diseases continued to smoke more than healthy individuals. Incident heart disease and asthma, but not incident COPD, stroke or diabetes were associated with a higher chance of quitting. Special focus on smokers with COPD, asthma, diabetes, stroke and ischemic heart disease/heart failure is warranted to decrease smoking prevalence in these groups. Smokers with a new diagnosis of diabetes, stroke and COPD need special smoking cessation support.