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Here is a new study  (popular press article) that caught my attention. After following nearly 30,000 Swedish women for 20 years, the researchers found those with the highest intentional sun exposure lived 0.6 - 2.1 years longer on average. While the rate of skin cancer in the high exposure group was higher, they died less from CVD and non-cancer / non-CVD causes during the study, which more than made up for the extra few deaths from skin cancer. The authors suggest it may be the health benefits of higher vitamin D or melatonin that is responsible for the reduced mortality in sun-lovers. I'm not going to go into great depth on this one, because I think the study is pretty flawed. First, Sweden is a very northerly country with an average latitude of 62°. That is equivalently far north as Anchorage Alaska. So people are probably more likely to be vitamin D deficient living that far north, and even a high amount of sun exposure at such northerly latitudes is unlikely to have the same effects (either good or bad) as sun exposure at more southerly points on the globe where most of the world live. But I think the biggest problem is the vast difference in other demographic and behavioral characteristics between those who got a lot of sun exposure and those who didn't. At study entry, compared to those who avoided the sun, those that got a lot of sun were: younger, less obese/overweight, more physically active, wealthier, less likely to suffer from a comorbidity, better educated, smoked more, and drank more alcohol. Of course they tried to statistically factor these differences out. But with so many differences between sun-avoiders and sun-worshippers, it's really difficult to determine cause and effect. In other words, is sun exposure really causing increased longevity, or simply a markers for a healthier lifestyle, or better health in general? The authors acknowledge this serious shortcoming in the discussion section: We acknowledge several major limitations of this study. First, it is not possible to differentiate between active sun exposure habits and a healthy lifestyle, and secondly, the results are of an observational nature; therefore, a causal link cannot be proven. So the takeaway is their might be benefits to sun exposure - at least for people living in northern climates. But I'd definitely continue to use sunscreen, particularly if you live more south than Sweden. --Dean ---------  J Intern Med. 2016 Mar 16. doi: 10.1111/joim.12496. [Epub ahead of print] Avoidance of sun exposure as a risk factor for major causes of death: a competing risk analysis of the Melanoma in Southern Sweden cohort. Lindqvist PG(1), Epstein E(2), Nielsen K(3), Landin-Olsson M(4), Ingvar C(5), Olsson H(6). Free Full text: http://onlinelibrary.wiley.com/doi/10.1111/joim.12496/epdf OBJECTIVE: Women with active sunlight exposure habits experience a lower mortality rate than women who avoid sun exposure; however, they are at an increased risk of skin cancer. We aimed to explore the differences in main causes of death according to sun exposure. METHODS: We assessed the differences in sun exposure as a risk factor for all-cause mortality in a competing risk scenario for 29 518 Swedish women in a prospective 20-year follow-up of the Melanoma in Southern Sweden (MISS) cohort. Women were recruited from 1990 to 1992 (aged 25-64 years at the start of the study). We obtained detailed information at baseline on sun exposure habits and potential confounders. The data were analysed using modern survival statistics. RESULTS: Women with active sun exposure habits were mainly at a lower risk of cardiovascular disease (CVD) and noncancer/non-CVD death as compared to those who avoided sun exposure. As a result of their increased survival, the relative contribution of cancer death increased in these women. Nonsmokers who avoided sun exposure had a life expectancy similar to smokers in the highest sun exposure group, indicating that avoidance of sun exposure is a risk factor for death of a similar magnitude as smoking. Compared to the highest sun exposure group, life expectancy of avoiders of sun exposure was reduced by 0.6-2.1 years. CONCLUSION: The longer life expectancy amongst women with active sun exposure habits was related to a decrease in CVD and noncancer/non-CVD mortality, causing the relative contribution of death due to cancer to increase. PMID: 26992108