Impact of Time Period and Birth Cohort on the Trend of Advanced Neoplasm Prevalence in the 40–49 Average-Risk Screening Population

Abstract

Early-onset colorectal cancer (CRC) is increasing globally. While the United States have lowered the age of initiation of screening to 45, other countries still start screening at age 50. In Taiwan, the incidence of CRC has declined in 55-74 year-olds after the initiation of screening, but still increased in those 50-54, potentially due to rising precancerous lesion incidence in 40-49 year-olds. This study aimed to explore the chronological trend of the prevalence of colorectal advanced neoplasms (AN) in the screening population aged 40-54. We retrospectively analyzed a screening colonoscopy cohort for prevalence of AN in average-risk subjects aged 40-54 from 2003 to 2019. Logistic regression was used to distinguish cohort effect from time-period effect on the prevalence of AN. In total, 27,805 subjects (52.1% male) men were enrolled. There were notable increases in prevalence of AN in all three age groups during the 17-year span, but these were more rapid in age 40-44 (0.99% to 3.22%) and 45-49 (2.50% to 4.19%). Age 50-54 had higher risk of AN [aOR=1.62(1.19-2.19)] in 2003-2008 but not in later periods [2009-2014: aOR=1.08(0.83-1.41)] and [2015-2019: aOR=0.76(0.56-1.03)] when compared with age 45-49. The prevalence of AN in age 40-54 increased in the Taiwanese population, with a later birth cohort having a higher prevalence of AN. However, the prevalence of AN in age 45-49 increased more remarkably and approximated that in age 50-54, which may justify earlier initiation of CRC screening at age 45.