Tan? Vitamin D? Or Both?

[Don Smith]

The abstract of the study shown below sows that the "more continuous Pattern" of sunlight exposure involved with occupational sun exposure "was not positively associated with melanoma risk overall or at different body sites in both studies."

Is this because of the photoprotective properties of facultative pigmentation, i.e., a "tan". Or because of the benefits of an increased level of vitamin D? Or both? My "guess" is that both the tan (which increases the individuals TUVR (tolerance to UVR) and the increased level of vitamin d are involved.

So a question: If, as this study shows, a more continuous pattern of sunlight exposure is not associated with increased CMM risk, wouldn't it follow that maintaining a tan year-round would be beneficial?


Int J Cancer. 2013 Nov 13. doi: 10.1002/ijc.28603. [Epub ahead of print]
Occupational sun exposure and risk of melanoma according to anatomical site.
Vuong K, McGeechan K, Armstrong BK; AMFS Investigators; GEM Investigators, Cust AE.
Source

Cancer Epidemiology and Services Research, Sydney School of Public Health, University of Sydney, NSW, Australia.
Abstract

Although sunburn and intermittent sun exposures are associated with increased melanoma risk, most studies have found null or inverse associations between occupational (more continuous pattern) sun exposure and melanoma risk. The association of melanoma with occupational sun exposure may differ according to anatomical site, with some studies finding a positive association with melanoma on the head and neck.

We examined the association between occupational sun exposure (self-reported weekday sun exposure) and melanoma risk according to anatomical site, using data from two multicentre population-based case-control studies: the Australian Melanoma Family Study (588 cases, 472 controls) and the Genes, Environment and Melanoma study (GEM; 1079 cases, 2,181 controls). Unconditional logistic regression was used to estimate odds ratios (OR) and their 95% confidence intervals, adjusting for potential confounders.

Occupational sun exposure was not positively associated with melanoma risk overall or at different body sites in both studies. The GEM study found inverse associations between occupational sun exposure and melanoma on the head and neck [OR for highest vs. lowest quartile: 0.56, 95% confidence intervals (CI) 0.36-0.86, ptrend 0.02], and between the proportion of total sun exposure occurring on weekdays and melanoma on the upper limbs (OR for highest vs. lowest quartile: 0.66, 95% CI 0.42-1.02, ptrend 0.03).

Our results suggest that occupational sun exposure does not increase risk of melanoma, even of melanomas situated on the head and neck. This finding seemed not to be due to negative confounding of occupational sun exposure by weekend sun.

[peach]

Again, great information-but a big "duh". Of course pigmentation tends to prevent skin cancer! Why do people have different skin colors to begin with? Those who live closer to the equator have different colored skin for a reason. How many African and South Americans get melanoma?