If you want to guard your wellbeing against rheumatoid arthritis, all you need to do is get some rays. This is according to a study from researchers at Harvard School of Public Health in Boston, who found that soaking up the sun may reduce a woman’s risk of rheumatoid arthritis (RA) by more than a fifth.
The research, led by Dr Elizabeth Arkema, was based on data from the Nurses’ Health Study. This is a major US investigation which looks at lifestyle factors affecting women’s health, and the scientists examined the conditions where the women lived to work out their likely exposure to UV-B rays. You know that over-exposure to the sun’s ultraviolet (UV) rays can damage your skin and trigger skin cancer, but the results of the study of more than 200,000 women, which was published in the journal Annals of the Rheumatic Diseases, suggests sunshine can also cut your RA risk by 21%.
A sensitive measurement method known as UV-B flux, which takes latitude, altitude and cloud cover into account, was used by the researchers. They expressed their results in terms of R-B units which relate to the impact of exposure over time. For example, 440 R-B units in 30 minutes would produce slight redness in untanned white skin. On average, the study’s volunteers had different R-B ratings, depending on the US state they were from. In the northern states of Alaska and Oregon, the annual average of exposure was 93 R-B units, which ranged right up to 196 R-B units in Hawaii and Arizona.
The study lasted up to three decades, and during that time 1,314 women developed RA, an auto-immune condition that attacks the joints. Those on the higher end of the R-B scale were 21% less likely to develop the disease than those with less sun exposure. However, the association was only seen in older women, which the researchers surmised may be because these women, who knew less about UV damage in their youth as we do know, were less likely to protect themselves from the sun.
According to the scientists, ‘Our study adds to the growing evidence that exposure to UV-B light is associated with decreased risk of rheumatoid arthritis. The mechanisms are not yet understood, but could be mediated by the cutaneous (skin) production of vitamin D and attenuated by use of sunscreen or sun-avoidant behaviour.’ They added that it is unclear whether RA risk is affected by sun exposure at birth, in adolescence or throughout adulthood.
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