title: Ultraviolet sunlight exposure during adolescence and adulthood and breast cancer risk: a population-based case-control study among Ontario women.
abstract: Recent studies suggest that vitamin D may be associated with reduced breast cancer risk, but most studies have evaluated only dietary vitamin D intake. The associations among ultraviolet radiation from sunlight, factors related to cutaneous vitamin D production, and breast cancer risk were evaluated in a population-based case-control study conducted in Ontario, Canada, between 2003 and 2004 (n = 3,101 cases and n = 3,471 controls). Time spent outdoors was associated with reduced breast cancer risk during 4 periods of life (>21 vs. ≤6 hours/week age-adjusted odds ratio (OR) = 0.71, 95% confidence interval (CI): 0.60, 0.85 in the teenage years; OR = 0.64, 95% CI: 0.53, 0.76 in the 20s-30s; OR = 0.74, 95% CI: 0.61, 0.88 in the 40s-50s; and OR = 0.50, 95% CI: 0.37, 0.66 in the 60s-74 years). Sun protection practices and ultraviolet radiation were not associated with breast cancer risk. A combined solar vitamin D score, including all the variables related to vitamin D production, was significantly associated with reduced breast cancer risk. These associations were not confounded or modified by menopausal status, dietary vitamin D intake, or physical activity. This study suggests that factors suggestive of increased cutaneous production of vitamin D are associated with reduced breast cancer risk.
authors.affiliation: Prevention and Cancer Control, Cancer Care Ontario, Toronto, Canada. LN.Anderson@utoronto.ca
authors.forename: Laura N
authors.initials: LN
authors.lastname: Anderson
authors.forename: Michelle
authors.initials: M
authors.lastname: Cotterchio
authors.forename: Victoria A
authors.initials: VA
authors.lastname: Kirsh
authors.forename: Julia A
authors.initials: JA
authors.lastname: Knight
mesh_terms: D000293:Adolescent; D000328:Adult; D000367:Age Factors; D000368:Aged; D001943:Breast Neoplasms / Q000453:epidemiology / Q000209:etiology*; D016022:Case-Control Studies; D016001:Confidence Intervals; D004781:Environmental Exposure / Q000706:statistics & numerical data; D005260:Female; D006801:Humans; D008875:Middle Aged; D016017:Odds Ratio; D009864:Ontario / Q000453:epidemiology; D012307:Risk Factors; D013472:Sunlight; D011795:Surveys and Questionnaires; D014466:Ultraviolet Rays; D014807:Vitamin D / Q000502:physiology
chemical_list: D014807:Vitamin D