XXXX risk factors and age at diagnosis: an Icelandic cohort study.

@entity1 @entity5 @entity0
An increasing number of studies indicates that the strength and even direction of association between @entity0 and established risk factors differ according to the @entity1 's age when she develops the disease. This was studied in the setting of a population based @entity5 registry using a databank with information on age at menarche, parity, age at first birth, oral contraceptive (OC) use, lactation, height and weight. From a cohort of 80.219 @entity1 attending population-based cervical and @entity0 screening in Iceland, 1120 cases were identified, aged 26-90 years at diagnosis and 10,537 controls, individually matched to the cases on birth year and age when attending. Information given at last visit before diagnosis was used in the analysis, applying conditional logistic regression. Odds ratios and statistical strength of relationships varied according to age at diagnosis for age at first birth, number of births, duration of lactation, height and weight. The decreased risk associated with young age at first birth and increasing duration of breast feeding became less pronounced with advancing age at diagnosis. A reduced risk associated with an increasing number of births was not detected in @entity1 diagnosed under the age of 40. An increased risk associated with giving first birth after 30 years of age was mainly detected in @entity1 who had only given 1 birth and were diagnosed under the age of 40 (OR = 7.06 95% CI = 2.16-23.01). A positive association with height and especially with weight was confined to @entity1 diagnosed after the age of 55. The results confirm that age at diagnosis should be taken into account when studying the effects of @entity0 risk factors.
