• Chia-Hsuin Chang, Jou-Wei Lin, and Yu-Kang Tu.
• Institute of Epidemiology and Preventive Medicine, College of Public Health, National Taiwan University, 5F, No. 17, Xu-Zhou Road, Taipei, Taiwan; Department of Internal Medicine, National Taiwan University Hospital, No. 7, Chung-Shan South Road, Section 1, Taipei, Taiwan; Department of Medicine, College of Medicine, National Taiwan University, No. 1, Jen-Ai Road, Section 1, Taipei, Taiwan.
• J Clin Epidemiol. 2015 Apr 1;68(4):405-11.

ObjectivesThe objective was to evaluate time-trend bias in the context of a series of studies reporting that a national hepatitis B virus vaccination program (launched in mid-1980s) substantially reduced childhood hepatocellular carcinoma (HCC) incidence.Study Design And SettingWe applied an age-period-cohort model to evaluate the relative importance of age, time-trend (period), and vaccination (cohort) effect, respectively, on the incidence and mortality rate of HCC in boys and girls in Taiwan from 1980 to 2009.ResultsHCC incidence increased with age. The period effect analysis revealed that the incidence of HCC started to decrease in 1980s, leveled off in mid-1990s, and declined again in mid-2000s among boys. The period effect was flat among girls. Cohort effect analysis demonstrated that among boys, the incidence of HCC started to decrease by those born in 2000-2004, which was 15 years later than the first vaccinated cohort. Among girls, the incidence rate started to decline before the mass vaccination program was initiated. The analysis showed a decline in mortality for boys and girls born in 1980s.ConclusionTime trend may play a more important role than the universal vaccination program in interpretation of the observed early decreasing trend in HCC in children, especially among boys.Copyright © 2015 Elsevier Inc. All rights reserved.

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