title: Relationship between low ultraviolet B irradiance and higher breast cancer risk in 107 countries.
abstract: Epidemiological data show an inverse relationship between vitamin D levels and breast cancer incidence. This study investigates the relationship of modeled and measured serum 25-hydroxyvitamin D [25(OH)D] levels with age-standardized incidence rates of breast cancer in 107 countries. The hypothesis being tested is that breast cancer incidence is inversely related to geographically-dependent cutaneous sunlight exposure. A multiple regression approach was used to examine the contributions of ultraviolet B (UVB) irradiance to age-standardized incidence rates of breast cancer in the 107 countries with data on these covariates-total column ozone thickness, per capita intake of alcohol and energy from animal and vegetable sources, cigarettes, proportion of female population overweight, and total fertility. Age-standardized incidence rates were substantially higher at latitudes distant from the equator (R2 = 0.43, p < 0.0001). The dose-response gradient between modeled serum 25(OH)D levels and incidence rates of breast cancer followed a standard inverse dose-response curve. Increasing increments in serum 25(OH)D in the range above 22 ng/mL were associated with incrementally lower incidence rates of breast cancer. According to multiple regression, UVB irradiance adjusted for cloud cover was inversely associated with incidence rates (p = 0.04) after controlling for covariates. Intake of energy from animal sources was also positively associated with incidence rates (p < 0.01). The overall coefficient of determination, R2, was 0.81 (p < 0.0001). There was a protective effect of UVB irradiance on risk of breast cancer that was independent of fertility rate, proportion of the population overweight, alcohol intake, animal energy intake, and other covariates.
authors.affiliation: Department of Family and Preventive Medicine, University of California San Diego, La Jolla, California 92093-0631, USA.
authors.forename: Sharif B
authors.initials: SB
authors.lastname: Mohr
authors.forename: Cedric F
authors.initials: CF
authors.lastname: Garland
authors.forename: Edward D
authors.initials: ED
authors.lastname: Gorham
authors.forename: William B
authors.initials: WB
authors.lastname: Grant
authors.forename: Frank C
authors.initials: FC
authors.lastname: Garland
mesh_terms: D000328:Adult; D001943:Breast Neoplasms / Q000097:blood / Q000209:etiology*; D005260:Female; D006801:Humans; D008875:Middle Aged; D012307:Risk Factors; D013472:Sunlight; D014466:Ultraviolet Rays; D014807:Vitamin D / Q000031:analogs & derivatives / Q000097:blood; D014808:Vitamin D Deficiency / Q000150:complications
chemical_list: D014807:Vitamin D; C104450:25-hydroxyvitamin D