Epidemiology of HPV infection among Mexican women with normal cervical cytology

Cervical cancer is caused by human papillomavirus (HPV) and is the most com mon cancer among Mexican women, but no population-based studies have report ed the prevalence and determinants of HPV infection in Mexico. A population -based study was carried out between 1996 and 1999, based on an age-stratif ied random sample of 1,340 women with normal cytologic diagnoses from 33 mu nicipalities of Morelos State, Mexico. The prevalence of cervical HPV DNA w as determined by reverse line blot strip assay to detect 17 cancer-associat ed and 10 non-cancer-associated HPV types, Two peaks of HPV DNA prevalence were observed, A first peak of 16.7% was observed in the age group under 25 years, HPV DNA prevalence declined to 3.7% in the age group 35-44 years, t hen increased progressively to 23% among women 65 years and older. Cancer-a ssociated HPV types were the most common in all age groups; non-cancer-asso ciated HPV types were rare in the young and became more common linearly wit h age. Twenty-four types of HPV were detected; HPV 16, HPV 53, HPV 31 and H PV 18 were the most common, but none was present in more than 1.7% of subje cts, The main determinant of infection with both cancer-associated and non- cancer-associated HPV types was the number of sexual partners in all age gr oups. Less-educated women were at an increased risk of infection with cance r-associated but not with non-cancer-associated HPV types; low socioeconomi c status was associated with detection of non-cancer-associated HPV types. Among young women an increasing number of pregnancies was associated with l ower HPV detection and among older women low socioeconomic status was relat ed to increased HPV detection, particularly for the age group 35-54 years. Among women with cancer-associated HPV types, there was a higher intensity of polymerase chain reaction signal in younger than in older age groups (p < 0.001). We present additional evidence for the sexually transmitted natur e of HPV infection, regardless of age group and HPV type. We confirm previo us findings of a second peak of high-risk HPV infections in postmenopausal women, in this case with a clear predominance of cancer-associated HPV type s. In populations with this pattern, which can be related to reactivation o f latent HPV infections or high previous exposure in order women, screening with HPV testing can have a reduced specificity among older women if prope r cut-off points for HPV positivity are not used. Longitudinal studies of i mmune responses to HPV infection in different age groups are warranted. (C) 2001 Wiley-Liss, Inc.