Abstract
ObjectivesThe aim of this study was to examine the risk of bladder cancer according to the trajectory pattern of amount of smoking among Korean young adult men.MethodsSmoking status was assessed with a standardized questionnaire in the Korean Life Course Health Study (KLCHS). Trajectory analyses were performed among young adult men using seven repeated surveys of cigarette per day (CPD) every two years from 1992 to 2005. The occurrence of bladder cancer was tracked from 2006 to 2016. The Cox proportional models were used to calculate the hazard ratio (HR) (95% confidence interval) of smoking patterns on bladder cancer.ResultsThe mean (standard deviation) age of the 161,069 participants was 34.0 (3.9) years, and 2,280,143 person-years (PY) were examined during the follow-up period of 14.2 (median 14.3) years. During this period, 263 new cases of bladder cancer occurred (11.5/100,000 PY). Among the six trajectory groups (low steady, lowering, rise and fall, high steady, rise and sharp fall, and very high steady), there was a higher risk of developing bladder cancer in the all the other groups compared to the low steady group. The highest risk group was the very high steady group, with HR 2.83 (95% CI 1.79–4.49). In addition, the risk of bladder cancer was 2.61 (95% CI 1.50–4.54) in the rise and sharp fall group.ConclusionThe risk of bladder cancer did not show much difference according to trajectories, except for low steady group. Thus quitting smoking should be the priority to lower the risk of bladder cancer in smokers.
Highlights
While bladder cancer is a relatively rare cancer in Korea, globally the incidence is gradually increasing and has been reported to have a poor prognosis
Meta-analysis published by Dai et al reported that to date available evidence was insufficient to support an independent association between coffee consumption and bladder cancer risk [2]
There was an increased risk of bladder cancer related to higher coffee consumption among studies with fewer cases (RR high vs low = 1.38, 95% CI 1.05–1.81), smoking was poorly adjusted among these studies
Summary
While bladder cancer is a relatively rare cancer in Korea, globally the incidence is gradually increasing and has been reported to have a poor prognosis. A meta-analysis of the association between smoking and bladder cancer in 89 observational studies showed that the summary odds ratio of bladder cancer incidence was 3.14 times (2.53–3.75) in current smokers and 1.83 (1.52–2.14). It has been reported that second-hand smoking increases the risk of bladder cancer in non-smokers [10]. Case–control study conducted by Yu et al reported the positive association between coffee consumption and bladder cancer among never smokers but not in current smokers [3]. Meta-analysis published by Dai et al reported that to date available evidence was insufficient to support an independent association between coffee consumption and bladder cancer risk [2]. There was an increased risk of bladder cancer related to higher coffee consumption among studies with fewer cases (RR high vs low = 1.38, 95% CI 1.05–1.81), smoking was poorly adjusted among these studies
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