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More UVB is associated with less cancer – study of 450,000 people – April 2012

Prospective study of ultraviolet radiation exposure and risk of cancer in the U.S.

Int J Cancer. 2012 Apr 26. doi: 10.1002/ijc.27619.
Lin SW, Wheeler DC, Park Y, Cahoon EK, Hollenbeck AR, Michal Freedman D, Abne CC.

Cancer Prevention Fellowship Program, National Cancer Institute, Bethesda, MD; Division of Cancer Epidemiology & Genetics, National Cancer Institute, Bethesda, MD. lins4 at mail.nih.gov.

Ecologic studies have reported that solar ultraviolet radiation (UVR) exposure is associated with cancer, but little evidence is available from prospective studies.
We aimed to assess the association between an objective measure of ambient UVR exposure and risk of total and site-specific cancer in a large, regionally diverse cohort (450,934 white, non-Hispanic subjects (50-71 years old) in the prospective NIH-AARP Diet and Health Study) after accounting for individual-level confounding risk factors.

Estimated erythemal UVR exposure from satellite Total Ozone Mapping Spectrometer (TOMS) data from NASA was linked to the U.S. Census Bureau 2000 census tract (centroid) of baseline residence for each subject. We used Cox proportional hazards models adjusted for multiple potential confounders to estimate hazard ratios (HR) and 95% confidence intervals (CI) for quartiles of UVR exposure. Restricted cubic splines examined non-linear relationships.

Over 9 years of follow-up, UVR exposure was inversely associated with total cancer risk (N=75,917; highest vs. lowest quartile, HR=0.97 (0.95, 0.99), p-trend<0.001). In site-specific cancer analyses, UVR exposure was associated with

  • increased melanoma risk (highest vs. lowest quartile, HR=1.22 (1.13, 1.32), p-trend<0.001) and
  • decreased risk of Non-Hodgkin's lymphoma (HR=0.82 (0.74, 0.92)) and
  • colon (HR=0.88 (0.82, 0.96)),
  • squamous cell lung (HR=0.86 (0.75, 0.98)),
  • pleural (HR=0.57 (0.38, 0.84)),
  • prostate (HR=0.91 (0.88, 0.95)),
  • kidney (HR=0.83 (0.73, 0.94)), and
  • bladder (HR=0.88 (0.81, 0.96)) cancers (all p-trend<0.05).

We also found non-linear associations for some cancer sites, including the thyroid and pancreas.
Our results add to mounting evidence for the influential role of UVR exposure on cancer.

Copyright © 2012 UICC.

PMID: 22539073


Vitamin D Council/Dr. Grant on the article

Is UV radiation exposure correlated with cancer?
Posted on May 2, 2012 by Dr William Grant
A study published online by the International Journal of Cancer on April 26 found incidence rates of 12 types of cancer inversely correlated with solar erythemal UV doses in July.
Lin SW, Wheeler DC, Park Y, Cahoon EK, Hollenbeck AR, Michal Freedman D, Abnet CC.
Prospective study of ultraviolet radiation exposure and risk of cancer in the U.S. Int J Cancer. 2012 Apr 26.

The study drew from the National Institutes of Health-AARP (NIH-AARP) cohort of 450,934 white, non-Hispanic subjects aged 50-71 years. During up to nine years of follow-up to the end of 2006, 75,917 cases of cancer were identified. The UVB index was solar erythemal UV incident at the surface in July determined from the NASA satellite instrument, Total Ozone Mapping Spectrometer (TOMS) between 1978-1993 and 1996-2005. Erythemal UV includes the UVB region for vitamin D production, but also extends into the UVA region where no vitamin D is produced. Participants in the study were from six states California, Florida, Louisiana, New Jersey, North Carolina, and Pennsylvania and two metropolitan regions (Atlanta and Detroit).

Those with cancer were divided into four quartiles of July erythemal UV dose with approximately equal numbers of cases. Many cancer risk-modifying factors such as BMI, physical activity, and smoking were shown to be nearly equally present among those in the four quartiles. However, the authors admitted that there could be unaccounted for confounding factors not included in the study, such as moving from the residential location at time of enrollment.

The 12 types of cancer are bladder, colon, kidney, lung, pancreas, pleura, prostate, rectal, thyroid cancer, diffuse large B-cell, T-call, and non-Hodgkin’s lymphoma. In addition, non-significant inverse correlations were also found for gall bladder, larynx, small intestine, and stomach cancer and follicular lymphoma. Increased risk of lip cancer (nonsignificant) and melanoma and other non-epithelial skin cancer (significant) provided support for the UV index used. These findings largely support the findings in many ecological studies. 1

Surprisingly, cancers of female organs, breast, ovary and uterus, were not inversely correlated with the UV index. A possible reason is that women spend less time in the sun than men. Other studies have found significant inverse correlations for solar UVB doses for men but not women such as an ecological study of cancer mortality rates in California in the period 1950-64.2

As the authors note, this study provides additional strong support for the role of vitamin D in reducing risk of cancer as no other factor has been proposed to explain the link between solar UVB irradiance and cancer risk reduction, and there is good support for vitamin D reducing the risk of cancer in other studies.

References
1. Grant WB. Ecological studies of the UVB–vitamin D–cancer hypothesis; review. Anticancer Res. 2012;32(1):223-36.
2. Grant WB. An ecological study of cancer mortality rates in California], 1950–64, with respect to solar UVB and smoking indices. Dermatoendocrinol., epub April 2012
3. Lin SW, Wheeler DC, Park Y, Cahoon EK, Hollenbeck AR, Michal Freedman D, Abnet CC. Prospective study of ultraviolet radiation exposure and risk of cancer in the U.S. Int J Cancer. 2012 Apr 26. doi: 10.1002/ijc.27619.


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