Evaluating mammography screening in observational cohort designs: the importance of avoiding lead time bias.

Aims: To investigate the potential lead time bias of the evaluation model (extended follow-up for women diagnosed with breast cancer) used to evaluate mammography screening in a recent Danish study. This model was compared with two traditional models.

Methods: We retrieved data on women diagnosed with breast cancer in each county of Norway from 1986 to 2016.

Polycystic ovary syndrome and risk of breast cancer in premenopausal and postmenopausal women: a nationwide population-based cohort study.

Purpose: Although some reproductive and metabolic characteristics of polycystic ovary syndrome (PCOS) are known risk factors for breast cancer, the evidence regarding a potential association between PCOS and breast cancer is scarce. In this population-based cohort study including all 1,719,452 women born in Denmark between 1940 and 1993, we investigated the association between PCOS and breast cancer.

Methods: PCOS diagnoses, cancer diagnoses, covariates, migrations, and vital status were all obtained from national population and health registers.

Polycystic ovary syndrome and endometrial cancer risk: results from a nationwide cohort study.

Most previous studies found an elevated risk of endometrial cancer among women with polycystic ovary syndrome (PCOS). However, these had highly varying methods for ascertainment of PCOS diagnoses and limitations such as few exposed women and short follow-up. In this cohort study, we investigated the association between PCOS and endometrial cancer among women born in Denmark between January 1, 1940, and December 31, 1993 (n = 1 719 121).

School performance and educational achievement in children exposed to maternal cancer in utero.

Background: In utero exposure to maternal cancer and cancer treatment might influence the child's cognitive development. This study investigated if exposure to maternal cancer during fetal life impacted school performance and educational achievement as adults.

Methods: This nationwide retrospective cohort study identified all live-born children in Denmark between January 1978 and December 2013.

Risk of borderline ovarian tumors after fertility treatment - Results from a Danish cohort of infertile women.

Objective: Results from previous studies examining the association between fertility treatment and borderline ovarian tumors are inconsistent. The aim of this study was to investigate the association between fertility treatment and borderline ovarian tumors in a cohort of infertile women.

Methods: This cohort study was based on the Danish Infertility Cohort and included all infertile women aged 20-45 years living in Denmark between 1 January 1995 and 31 December 2017 (n = 146,891).