Chia-Hsuin Chang1, Jou-Wei Lin2, Yu-Kang Tu3. 1. 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. 2. 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; Department of Internal Medicine, National Taiwan University Hospital Yun-Lin Branch, 579 Yun-Lin Road, Section 2, Dou-Liou City, Yun-Lin County, Taiwan. Electronic address: jouweilin@yahoo.com. 3. Institute of Epidemiology and Preventive Medicine, College of Public Health, National Taiwan University, 5F, No. 17, Xu-Zhou Road, Taipei, Taiwan. Electronic address: yukangtu@ntu.edu.tw.
Abstract
OBJECTIVES: The 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 SETTING: We 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. RESULTS: HCC 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. CONCLUSION: Time 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.
OBJECTIVES: The 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 SETTING: We 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. RESULTS:HCC 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. CONCLUSION: Time 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.