竹井 裕二

Co-infections with human papillomavirus (HPV) of multiple genotypes mainly occur due to increased sexual activity. To address the prevalence and trend of HPV co-infections in Japan, HPV-type-specific data from Japanese women (n = 8128) aged < 40 years and newly diagnosed with cervical abnormalities at 24 hospitals between 2012 and 2023 were analyzed. These included cervical intraepithelial neoplasia grade 1/2 (CIN1/2, n = 2745), CIN3/adenocarcinoma in situ (AIS) (n = 3953), and invasive cervical cancer (ICC, n = 1430). For women enrolled in this study since 2019, information on sexual behaviors was collected via a self-administered questionnaire. Time-trend analyses by disease category showed significant declines in the prevalence of multiple HPV infections in CIN1/2 (49.1%-38.3%, ptrend = 0.0004), CIN3/AIS (44.7%-31.5%, ptrend = 0.0002), and ICC (26.7%-10.5%, ptrend < 0.0001) during the last decade. When these data were analyzed separately for women aged 20-29 and 30-39 years, similar declining trends were observed in each disease category. Using data from 2111 women for whom information on sexual history was available, the number of sexual partners was strongly associated with increased multiple HPV infections (p < 0.0001). In conclusion, the declining prevalence of HPV co-infections in cervical cancer and its precursors may reflect a decrease in sexual activity among Japanese women of reproductive age.