Skin Cancer Updates
Avoiding Sun: Dangerous as Smoking?
Nonsmokers who stayed out of the sun had a life expectancy similar to smokers who soaked up the most rays, according to researchers who studied nearly 30,000 Swedish women over 20 years. This indicates that avoiding the sun "is a risk factor for death of a similar magnitude as smoking," write the authors of the article, published March 21 in the Journal of Internal Medicine. Compared with those with the highest sun exposure, life expectancy for those who avoided sun dropped by 0.6 to 2.1 years.
Pelle Lindqvist, MD, of Karolinska University Hospital in Huddinge, Sweden, and colleagues found that women who seek out the sun were generally at lower risk for cardiovascular disease (CVD) and noncancer/non-CVD diseases such as diabetes, multiple sclerosis, and pulmonary diseases, than those who avoided sun exposure. And one of the strengths of the study was that results were dose-specific — sunshine benefits went up with amount of exposure.
The researchers acknowledge that longer life expectancy for sunbathers seems paradoxical to the common thinking that sun exposure increases risk for skin cancer. They found an increased risk of skin cancer . However, the skin cancers that occurred in those exposing themselves to the sun had better prognosis.
Some Daily Exposure Important for Health
The western world's restrictive guidance against sun exposure over the past 4 decades may be particularly ill-advised. People are probably using it to be out longer in the sun. Patients with more pigmentation should stop avoiding sunshine, as many people in India, for instance, follow guidelines like those in the western world. And because melanomas are rare among women with darker skin, benefit goes up in those populations when weighing sun exposure's risk against benefits.
Age and Smoking Habits
The researchers studied sun exposure as a risk factor for all-cause mortality for 29,518 women with no history of malignancy in a prospective 20-year follow-up of the Melanoma in Southern Sweden cohort. The women were recruited from 1990 to 1992 when they were 25 to 64 years old. Detailed information was available at baseline on sun-exposure habits and potential confounders such as marital status, education level, smoking, alcohol consumption, and number of births. When smoking was factored in, even smokers at approximately 60 years of age with the most active sun-exposure habits had a 2-year longer life expectancy during the study period compared with smokers who avoided sun exposure, the researchers note. The authors do, however, acknowledge some major limitations. Among them, it was impossible to differentiate between active sun-exposure habits and a healthy lifestyle, and they did not have access to exercise data.
UV radiation and melanoma
There can be no doubt that a relation exists between UV radiation and melanoma of the skin. Also, there is no doubt that UV radiation is a form of electromagnetic radiation that is capable of damaging cells in different ways. The depletion of the ozone layer over the last decades has become a cause for concern regarding skin and eye melanoma. But no strong increase in UV radiation due to ozone depletion was noticed as early as 1955. I wrote a sentinel paper on the increasing level of malignant melanoma between the period 1950-1985 back in the Mayo Clinic in 1989. Consequently, there must be something else that suddenly accelerated the transformation of damaged cells into skin cancer.
Role of FM/TV broadcasting networks
Research by Örjan Hallberg and Olle Johansson shows no evidence that increased travel is the main cause of increased mortality in malignant melanoma since 1955. We found, however, a strong connection between the start of FM broadcasting and increased mortality from malignant melanoma of the skin in all investigated countries. The fact that melanoma mortality starts to increase earlier than the incidence implies that an environmental factor other than sunshine affects the survival probability of melanoma patients. This is further underscored by the fact that melanoma deaths can show peaks of the kind noticed in France during 1968.
Role of Vitamin D Still in Question
The results add to the longstanding debate on the role of vitamin D in health and the amount of it people need, but this study doesn't resolve the question. Whether the positive effect of sun exposure demonstrated in this observational study is mediated by vitamin D, another mechanism related to ultraviolet radiation such as the release of nitrous oxide, or by unmeasured bias cannot be determined.
From Irish studies we know that vitamin D deficiency makes melanomas more malignant. This is in agreement with our results; melanomas of [those not exposed] to the sun had a worse prognosis.
This study was supported by the Clintec at the Karolinska Institute; ALF (Faculty of Medicine, Lund University, Region Skane); the Swedish Cancer Society; and the Swedish Medical Research Council. Funding was also received from Lund University Hospital; the Gustav V Jubilee Fund; the Gunnar Nilsson Foundation; the Kamprad Foundation; and the European Research Council. The authors declared no relevant financial relationships.
J Intern Med. Published online March 16, 2016. Article