Trends over time in the incidence of cervical neoplasia in comparison to trends over time in human papillomavirus infection

Introduction: The establishment of human papillomavirus (HPV) infection as a major cause of cervical neoplasia has resulted in major efforts to develo p prophylactic HPV vaccines for prevention of cervical neoplasia. Cervical cancer and the other HPV-associated cancers constitute a major public healt h burden and eradication of the major causative infection is certainly the most appealing long-term preventive measure. Nevertheless, the effects of p reventive HPV vaccination will need to be estimated and compared for (cost- ) efficacy with other primary prevention and with secondary prevention prog rams. However, estimating the effects of preventing a causative exposure is complicated when the exposure is a transmissible infection. The spread of the epidemic is dynamic and may change over time depending e.g. on the chan ges in human behavior. Depending on the circumstances, prevention of an inf ection may have either greater or lesser effects than the prevention of a n on-infectious exposure. Estimating the time trends in HPV infections and th e underlying trends in the risk of cervical neoplasia is important for esti mating effects of interventions. Method: A literature review on recent evid ence on time trends in cervical neoplasia, compared with evidences on time trends in HPV infections and interactions between different types of HPV in fections. Results: In Finland, there has between 1991 and 1995 been a 60% i ncrease in the incidence of cervical cancer among women <55 years of age. T rends in detection rates of cervical cancer precursor lesions are consisten t with an increase in the background cervical cancer risk. From the 1960s t o 1980s, there has been a major increase in HPV seroprevalences over time i n the Nordic countries. Increasing trends are also seen for other sexually transmitted diseases and smoking. Several studies indicate the existence of interaction between benign and oncogenic HPV types, thus making the relati onship between the incidences in HPV infections and in cervical neoplasia c omplex. Conclusion: The increase in cervical cancer is paralleled by increa ses in HPV infection, other STDs and smoking and changes in screening pract ices, all of which may have contributed. Prediction of the effect on cervic al cancer incidence of changes in HPV incidences is complicated by the exis tence of several risk factors, the protective effect of screening and by th e population dynamics of HPV infections. (C) 2000 Elsevier Science B.V. All rights reserved.