A Cohort Effect of the Sexual Revolution May Be Masking an Increase in Human Papillomavirus Detection at Menopause in the United States

Background. Cohort effects, new sex partnerships, and human papillomavirus (HPV) reactivation have been posited as explanations for the bimodal age-specific HPV prevalence observed in some populations; no studies have systematically evaluated the reasons for the lack of a second peak in the United States. Methods. A cohort of 843 women aged 35-60 years were enrolled into a 2-year, semiannual follow-up study. Age-specific HPV prevalence was estimated in strata defined by a lower risk of prior infection (<5 self-reported lifetime sex partners) and a higher risk of prior infection (>= 5 lifetime sex partners). The interaction between age and lifetime sex partners was tested using likelihood ratio statistics. Population attributable risk (PAR) was estimated using Levin's formula. Results. The age-specific prevalence of 14 high-risk HPV genotypes (HR-HPV) declined with age among women with <5 lifetime sex partners but not among women with >= 5 lifetime sex partners (P = .01 for interaction). The PAR for HR-HPV due to = 5 lifetime sex partners was higher among older women (87.2%), compared with younger women (28.0%). In contrast, the PAR associated with a new sex partner was 28% among women aged 35-49 years and 7.7% among women aged 50-60 years. Conclusions. A lower cumulative probability of HPV infection among women with a sexual debut before the sexual revolution may be masking an age-related increase in HPV reactivation in the United States.