Here’s another reason to let the sunshine in: New research has found regular exposure to sunlight may reduce a woman’s risk of developing rheumatoid arthritis.
The findings, which are based on a long-running study of nurses by Harvard School of Public Health researchers, indicate ultraviolet B (UVB) rays may be the most beneficial. But the effect of UVB exposure was only evident among older women, possibly because younger women are more aware of the hazards of sunlight and so cover up with sunscreen, researchers said.
The study, published online in the Annals of the Rheumatic Diseases, suggested vitamin D — produced when sunlight contacts the skin — is the likely culprit. But investigators said more research is needed to determine the cause of UVB’s protective action and quantify the risks and benefits of sun exposure, which can also cause skin cancer.
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“Our study adds to the growing evidence that exposure to UV-B light is associated with decreased risk of rheumatoid arthritis,” the researchers noted. “The mechanisms are not yet understood, but could be mediated by the cutaneous production of vitamin D and attenuated by use of sunscreen or sun avoidant behavior.”
For the study, researchers analyzed the medical records of women participating in the long-running Nurses’ Health Study, which tracked the health of more than 120,000 nurses between 1976 and 2008. A second phase of the study monitored the health of an additional 115,500 nurses between 1989 and 2009.
They compared UVB exposures and arthritis rates among women in both phases of the nurses study.
The results showed 1,314 nurses developed rheumatoid arthritis. Among the women in the first phase, nurses with the highest levels of UVB exposure were 21 percent less likely to develop rheumatoid arthritis than those with the least, the analysis showed. But among women the second phase of the nurses study, the researchers found no association between UVB exposure and arthritis, possibly because they were younger and more savvy about the potential hazards of tanning.
“Differences in sun protective behaviors [e.g. greater use of sun block in younger generations] may explain the disparate results,” they said.
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