-- Robert Preidt
TUESDAY, Feb. 5 (HealthDay News) -- Older women who've had
regular exposure to sunlight may be less likely to develop
rheumatoid arthritis, new findings indicate.
This beneficial effect -- which is believed to be due to
ultraviolet B (UV-B) in sunlight -- was only evident in older
women. This may be because younger women are more aware of the
skin-related hazards of sunlight and take more steps to limit their
exposure, the researchers said.
For the study, the investigators looked at about 235,000
participants who took part in two phases of the U.S. Nurses' Health
Study. The first phase began in 1976 with nurses aged 30 to 55 and
continued until 2008. The second phase began in 1989 with nurses
aged 25 to 42 and continued until 2009.
By the end of the two phases, 1,314 of the women had developed
rheumatoid arthritis, according to the study published in the
current online edition of the journal
Annals of the Rheumatic Diseases.
The nurses' UV-B exposure was estimated based on data from the
states where they lived while taking part in the study. Likely
estimates of their UV-B exposure at birth and by age 15 were also
Among women in the first phase of the Nurses' Health Study,
those with the highest estimated levels of UV-B exposure were 21
percent less likely to develop rheumatoid arthritis than those with
the lowest levels.
However, no such association between UV-B exposure and
rheumatoid arthritis risk was seen among women in the second phase.
These women were younger than those in the first phase and may have
been more aware about the dangers of too much sun exposure and
avoided it, the study authors suggested.
"Our study adds to the growing evidence that exposure to UV-B light is associated with decreased risk of rheumatoid arthritis," concluded Dr. Elizabeth Arkema, of the department of epidemiology at Harvard School of Public Health, and colleagues.
But even though the researchers found an association between
greater estimated exposure to UV-B light and lower risk of
rheumatoid arthritis in the women in the first phase of the Nurses'
Health Study, the finding did not prove that there was a
It's not known how UV-B exposure might reduce the risk of
rheumatoid arthritis, but it could be due to the skin's production
of vitamin D in response to sunlight, the study authors suggested
in a journal news release.
The American Academy of Family Physicians has more about
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