Low ultraviolet B and increased risk of brain cancer: an ecological study of 175 countries.
BACKGROUND
The purpose of this study was to determine whether an inverse association exists between latitude, solar ultraviolet B (UVB) irradiance, modeled 25-hydroxyvitamin D [25(OH)D] levels and incidence rates of cancer of the brain.


METHODS
Associations of latitude and UVB irradiance with age-standardized incidence rates of cancer of the brain were analyzed for 175 countries while controlling for proportion of population overweight, energy from animal sources, fish consumption, cigarette and alcohol consumption and per capita health expenditures, using multiple regression. Serum 25(OH)D levels were modeled for each country, and their association with brain cancer also was determined.


RESULTS
The incidence rates of brain cancer were higher at higher latitudes (R(2) for males = 0.45, p ≤ 0.0001; R(2) for females = 0.35, p < 0.0001). After adjustment for potential confounders, UVB irradiance (p ≤ 0.0001) and modeled serum 25(OH)D were inversely associated with incidence rates.


CONCLUSIONS
Countries with low solar UVB irradiance and estimated mean serum 25(OH)D levels generally had higher age-standardized incidence rates of brain cancer. Since this was an ecological study, further research would be worthwhile on the association of prediagnostic serum 25(OH)D with incidence rate in studies of cohorts of individuals.
Department of Family and Preventive Medicine, University of California San Diego, La Jolla, CA 92093-0620, USA.
Sharif B
SB
Mohr
Edward D
ED
Gorham
Cedric F
CF
Garland
William B
WB
Grant
Frank C
FC
Garland
D017677:Age Distribution; D001932:Brain Neoplasms / Q000453:epidemiology* / Q000209:etiology*; D004032:Diet; D004307:Dose-Response Relationship, Radiation; D055669:Ecological and Environmental Phenomena; D005260:Female; D005396:Fish Products; D005843:Geography; D006801:Humans; D015994:Incidence; D038622:Internationality; D016014:Linear Models; D008297:Male; D009381:Neoplasms, Radiation-Induced; D018570:Risk Assessment; D017678:Sex Distribution; D013472:Sunlight / Q000009:adverse effects; D014466:Ultraviolet Rays / Q000009:adverse effects*; D014807:Vitamin D / Q000031:analogs & derivatives / Q000097:blood
D014807:Vitamin D; C104450:25-hydroxyvitamin D