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Br J Dermatol. 2019 Feb 12. doi: 10.1111/bjd.17771. [Epub ahead of print]

Reproductive factors and risk of melanoma: a population-based cohort study.

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Norwegian National Advisory Unit on Women's Health, Women's Clinic, Oslo University Hospital, Oslo, Norway.
Department of Bowel Cancer Screening, Cancer Registry of Norway, Institute of Population-Based Cancer Research, Oslo University Hospital, Oslo, Norway.
Oslo Centre for Biostatistics and Epidemiology, Department of Biostatistics, Institute of Basic Medical Sciences, University of Oslo, Oslo, Norway.
Department of Community Medicine, University of Tromsø, The Arctic University of Norway, Tromsø, Norway.
Institute of Clinical Medicine, University of Oslo, Oslo, Norway.
Department of Research, Cancer Registry of Norway, Institute of Population-Based Cancer Research, Oslo University Hospital, Oslo, Norway.
Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, Stockholm, Sweden.
Genetic Epidemiology Group, Folkhälsan Research Center, Faculty of Medicine, University of Helsinki, Helsinki, Finland.



The association between reproductive factors and risk of cutaneous melanoma (CM) is unclear. We investigated this issue in the Norwegian Women and Cancer (NOWAC) cohort study.


To examine the association between the reproductive factors age at menarche, menstrual cycle length, parity, age at first and last birth, menopausal status, breastfeeding duration and length of ovulatory life and CM risk, overall and by histological subtypes and anatomical site METHODS: We followed 165,712 women aged 30-75 at inclusion from 1991-2007 to the end of 2015. Multivariable Cox regression was used to estimate hazard ratios (HRs) with 95% confidence intervals (CIs).


The mean age at cohort enrolment was 49 years. During a median follow-up of 18 years, 1,347 CM cases were identified. No reproductive factors were clearly associated with CM risk. When stratifying by histological subtype we observed significant heterogeneity (p = 0.01) in the effect of length of ovulatory life on the risk of superficial spreading melanoma (HR 1.02, 95% CI 1.01-1.04 per year increase) and nodular melanoma (HR 0.97, 95% CI 0.94-1.01 per year increase). When stratifying by anatomical site, menopausal status (HR 0.54, 95% CI 0.31-0.92, postmenopausal compared to premenopausal) and menstrual cycle length (HR 1.07, 95% CI 1.01-1.13, per day increase) were associated with CM of the trunk, and significant heterogeneity between anatomical sites was observed for menopausal status (p = 0.04).


In this large population-based Norwegian cohort study, we did not find convincing evidence of an association between reproductive factors and risk of CM. This article is protected by copyright. All rights reserved.


hormones; melanoma; menstrual cycle; prospective cohort study; reproductive factors


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