Increasing risk of uterine cervical cancer among young Japanese women: Comparison of incidence trends in Japan, South Korea and Japanese-Americans between 1985 and 2012.

In Japan, cervical cancer incidence has increased since the late 1990s especially among young women, despite a decreasing trend in most developed countries. Here, we examined age, period and birth cohort trends in cervical cancer incidence rates from 1985 to 2012. Incidence rates were ascertained using three population-based cancer registries and analyzed using Joinpoint regression and age-period-cohort models. We compared the findings in Japan to trends among Japanese-Americans in the Surveillance, Epidemiology, and End Results Registries and among women in South Korea using the Korea Central Registry. Age-standardized incidence rates in Japan decreased by 1.7% per year (95% confidence interval - 3.3%, 0.0%) until 1997 and thereafter increased by 2.6% per year (1.1%, 4.2%). Incidence rates increased among women under age 50, were stable among women aged 50-54, and decreased or remained stable among women aged 55 and over. The age-standardized incidence rate ratio by birth cohort showed a U-shaped pattern with the lowest rates in women born in the late 1930s and 1940s. In comparison, women born before 1920 and after 1970 had about double the incidence. Increasing risk in recent birth cohorts was not evident in Japanese-American or South Korean women. The trends in Japan may be attributable to increasing prevalence of human papillomavirus (HPV) infection among young women. Screening and vaccination have been shown to be highly effective and would help reverse these trends.