The influence of reproductive variables on cervical cancer incidence, controlling for other sociodemographic factors, was estimated in Norwegian register and census data, using Poisson regression models. Among the 1.3 million women under observation, a total of 2,870 cases of cervical cancer were diagnosed. According to models restricted to parous women, parity level had no independent impact on cervical cancer incidence, but a clear effect of age at first birth was noted. It was most pronounced in the squamous cell carcinomas, where the incidence was reduced by 48 percent from age at first birth <21 years="" to="" age="" at="" first="" birth="" 27+years.="" women="" without="" children="" had="" the="" same="" cervical="" cancer="" incidence="" as="" parous="" women="" with="" a="" first="" birth="" after="" age="" 24.="" the="" sociodemographic="" variables="" controlled="" for="" exerted="" a="" strong="" net="" effect="" on="" the="" cervical="" cancer="" incidence.="" educational="" level="" was="" related="" inversely="" to="" the="" cancer="" risk.="" moreover,="" an="" increased="" risk="" was="" seen="" for="" women="" who="" had="" given="" birth="" when="" they="" were="" still="" single="" (never="" married)="" and="" for="" those="" who="" were="" divorced/separated="" at="" the="" time="" of="" the="" last="" previous="" census.="" a="" fairly="" small="" excess="" risk="" was="" found="" to="" be="" associated="" with="" living="" in="" non-rural="" compared="" with="" rural="">
Key words Cervical cancer - Norway - reproductive variables
Dr Bjørge is with the Cancer Registry of Norway, Oslo, Norway. Dr Kravdal is with the Section for Demography, Department of Economics, University of Oslo, Oslo, Norway. Address correspondence to Dr Bjørge, the Cancer Registry of Norway, Institute for Epidemiological Cancer Research, Montebello, N-0310 Oslo, Norway. This work was supported by grant no. 95034/001 from the Norwegian Cancer Society.