A new study out of Sweden and published on Medscape, which is an online magazine for doctors, reported that nonsmokers who stayed out of the sun had a life expectancy similar to that of smokers who soaked up the most rays. Hence, not getting sufficient sunlight is as dangerous and life-shortening as smoking. The study involved 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 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 such diseases 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 the 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.
"We did find an increased risk of.skin cancer. However, the skin cancers that occurred in those exposing themselves to the sun had better prognosis," Dr Lindqvist said.
Some Daily Exposure Important for Health
Given these findings, he told Medscape Medical News, women should not overexpose themselves to sun, but underexposure may be even more dangerous.
"We know in our population, there are three big lifestyle factors that endanger health: smoking, being overweight, and inactivity," he said. "Now we know there is a fourth — avoiding sun exposure."
Sweden's restrictive guidance against sun exposure over the past 4 decades may be particularly ill-advised, the study finds, in a country where the maximum UV index is low (< 3) for up to 9 months out of the year.
Use of sunscreen is also widely misunderstood in the country and elsewhere, Dr Lindqvist said.
"If you're using it to be out longer in the sun, you're using it in the wrong manner," he said. However, "If you are stuck on a boat and have to be out, it's probably better to have sunscreen than not to have it."
Women with more pigmentation would be particularly well-served to stop avoiding sunshine, he said, adding that many people in India, for instance, follow guidelines like those in Sweden to avoid sun year round.
And because melanomas are rare among women with darker skin, benefit goes up in those populations when weighing sun exposure's risk against benefits, Dr Lindqvist said.
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.
.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, or by unmeasured bias cannot be determined. Therefore, additional research is warranted," the authors write.
Dr. Cinque: Even the role of sunlight in causing skin cancer is not fully understood because it is not uncommon for people to develop skin cancers in areas which have not been over-exposed. Likewise, there are plenty of areas which, which for some people, are chronically over-exposed- say the arms of a fisherman- where the incidence of skin cancers doesn't correlate. Protecting the skin from too much sun exposure is definitely a good idea, apart from cancer, because we know it ages the skin and damages it. But, there are plenty of people who want to avoid the sun completely, and that is wrong. The sun's ultraviolet has a powerful anti-cancer effect which seems to work against every kind of cancer except skin cancer. And yes, skin cancer can be deadly, but caught early, it is about the easiest cancer to treat. Here's a good rule of thumb: if the sun exposure you are are getting is causing frank, visible tanning, then you're getting too much sun. The frank, visible tanning is a reaction to too much sun. And here's another good rule: if you want to protect your face all the time, it's fine. You are not going to suffer if that small part of your body doesn't get exposed to the sun. But, find large, broad areas of yourself that you can expose directly to effective sunlight for 10 or 15 minutes at a time. There is more danger if you don't than if you do.