title: A population-based cross-sectional study of age-specific risk factors for high risk human papillomavirus prevalence in rural Nigeria.
abstract: BACKGROUND
  Cervical cancer, caused by persistent infection with carcinogenic human papillomavirus (HR-HPV), is particularly prevalent in Sub-Saharan Africa and is associated with a high mortality rate. Some studies in West Africa, including our own, have found unusually high HR-HPV across all ages with a slight peak in older women. This increased prevalence at older ages may complicate screen-and-treat programs, which are implemented in regions where HPV prevalence declines with age and typically target women between 30-49 years. A better understanding of the determinants of high HR-HPV prevalence at older ages is needed. The goal of this study is to explore risk factors for HR-HPV prevalence by age among women in our population-based study in Irun, a rural town in southwestern Nigeria.
  
  
  METHODS
  1,420 women were administered a clinic-based questionnaire regarding sexual and reproductive behavior, marital status (including co-wives), and malaria exposure. Logistic regression compared questionnaire responses and PCR positivity for a set of 13 carcinogenic HR-HPV types. Results were stratified by age (15-29, 30-45, 46-55, and 56+ years).
  
  
  RESULTS
  Birth control use and age at first pregnancy were associated with HR-HPV (p-value = 0.03 and 0.05, respectively). Early age at sexual debut and multiple sex partners were risks for HR-HPV, but did not reach significance (p-value = 0.1 and 0.07, respectively). Neither self-reported malaria nor presence of co-wives in the household was associated with HR-HPV (p-value = 0.85 and 0.24, respectively). In age sub-categories, early age at sexual debut was a significant risk factor for HR-HPV among women 35-45 years (p-value = 0.02). Early age at first pregnancy remained a significant risk factor for women aged 56+ years (p-value = 0.04). Greater than 2 sex partners and use of birth control were associated (though not significantly) with HR-HPV in women aged 30-45 (p-value = 0.08, respectively).
  
  
  CONCLUSIONS
  In this high-risk region with elevated HR-HPV prevalence at older ages, we confirmed previously described, behavioral determinants of HR-HPV. There was no association with self-reported malaria or co-wives, which we had hypothesized might correlate with HR-HPV at older ages.
authors.affiliation: Division of Cancer Epidemiology and Genetics, National Cancer Institute, National Institutes of Health, DHHS, Bethesda, MD, USA. clarkma2@mail.nih.gov.
authors.forename: Megan A
authors.initials: MA
authors.lastname: Clarke
authors.forename: Julia C
authors.initials: JC
authors.lastname: Gage
authors.forename: Kayode O
authors.initials: KO
authors.lastname: Ajenifuja
authors.forename: Nicolas A
authors.initials: NA
authors.lastname: Wentzensen
authors.forename: Akinfolarin C
authors.initials: AC
authors.lastname: Adepiti
authors.forename: Sholom
authors.initials: S
authors.lastname: Wacholder
authors.forename: Robert D
authors.initials: RD
authors.lastname: Burk
authors.forename: Mark
authors.initials: M
authors.lastname: Schiffman