People residing at higher latitudes, who are exposed to lower levels of sunlight/ultraviolet B (UVB) light and have a higher prevalence of vitamin D deficiency, are at least twice as likely to develop leukemia than equatorial populations, according to a study published online in the journal PLOS ONE.

“These results suggest that much of the burden of leukemia worldwide is due to the epidemic of vitamin D deficiency we are experiencing in winter in populations distant from the equator,” said Cedric Garland, DrPH, adjunct professor in the Department of Family Medicine and Public Health and member of Moores Cancer Center at University of California San Diego Health.

For the study, researchers analyzed incidence rates of leukemia in 172 countries using information from an international agency for research on cancer called GLOBOCAN and cloud cover data from the International Satellite Cloud Climatology Project.

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Results showed that leukemia rates were highest in Australia, New Zealand, Chile, Ireland, Canada, and the United States, countries that are relatively closer to the poles. In contrast, leukemia rates were lowest in countries closer to the equator, such as Bolivia, Madagascar, Nigeria, and Samoa.

“People who live in areas with low solar ultraviolet B exposure tend to have low levels of vitamin D metabolites in their blood,” Garland said. “These low levels place them at high risk of certain cancers, including leukemia.”

Garland and colleagues have also found in other studies that reduced UVB radiation exposure and lower vitamin D levels were associated with higher risks of bladder, breast, colon, and pancreatic cancers and multiple myeloma.

“These studies do not necessarily provide final evidence,” Garland said, “but they have been helpful in the past in identifying associations that have helped minimize cancer risk.”


1. UC San Diego researchers link higher risk of leukemia to low sunlight and vitamin D [news release]. EurekAlert! Web site.–usd010616.php. Posted January 6, 2015. Accessed January 7, 2015.