Soaking up the sun may reduce a woman's risk of rheumatoid arthritis, a study has shown.
Over-exposure to the sun's ultraviolet (UV) rays can damage the skin and trigger skin cancer. But new research involving more than 200,000 women suggests sunshine can also cut the risk of rheumatoid arthritis (RA) by more than a fifth.
The findings are based on data from the Nurses' Health Study, a major US investigation looking at lifestyle factors affecting women's health.
Scientists looked at conditions where the women lived to work out their likely exposure to UV-B rays.
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The researchers used a sensitive measurement method known as UV-B flux which takes into account latitude, altitude and cloud cover.
It is expressed in R-B units which relate to the impact of exposure over time. A count of 440 R-B units in 30 minutes, for example, would produce slight redness in untanned white skin.
Study participants from US states with different climates had different R-B ratings, the research published in the journal Annals of the Rheumatic Diseases found.
Exposure ranged from an annual average of 93 R-B units in the northern states of Alaska and Oregon, to 196 in Hawaii and Arizona.
During the study period, which lasted up to three decades, a total of 1,314 women developed RA, an auto-immune condition that attacks the joints.
Those with the highest levels of exposure were 21% less likely to develop the disease than those with the lowest.
However, the association was only seen in older women enrolled at the start of the study in the 1970s. This might be because in their youth they were less likely to protect themselves from the sun than future generations, the researchers believe.
Previous studies have shown that people living in northern latitudes, where the sun is less intense, have a higher risk of RA, as well as other auto-immune conditions including Type 1 diabetes, inflammatory bowel disease and multiple sclerosis.
The scientists, led by Dr Elizabeth Arkema, from the Harvard School of Public Health in Boston, wrote: "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."
It is unclear whether RA risk is affected by sun exposure at birth, in adolescence or throughout adulthood, said the researchers.
Many study participants did not move home during their childhood and were still living in the same place they were born in at the age of 15.
The scientists acknowledged a lack of individual data on time spent outdoors, travel to sunny destinations, and sunscreen use. But they pointed out that UV-B flux had been shown to reflect the risk of non-melanoma skin cancer among the study participants. It could therefore be considered a "reasonable proxy" for sun exposure.
An old man in night-clothes holding up a box of "Uricure" pills as an advertisement for their efficacy against rheumatic diseases. Coloured lithograph by L. Cappiello, ca. 1910.
A swollen and inflamed foot; gout is represented as an attacking demon. Coloured etching, 1835
A self-indulgent man afflicted with gout: the pain is represented by a demon burning his foot. Coloured lithograph by G. Cruikshank, 1818, after Captain Hehl.
The inscription tells us much about the contents of the jar. Benedicta lar is a shortened version of Benedicta Laxativa – “the Blessed Laxative”. This preparation was so called to avoid confusion with similar but less valuable preparations. Made from a mixture of crushed seeds, plants, sugar and honey, the laxative was used to loosen and purge phlegm from the body. It was believed an excessive amount of cold phlegm, one of the four humours, caused trouble with the joints, such as arthritis and gout. Unknown maker, Italy, 1601-1700
The inscription on the jar is in Latin and translates as “Oil of Earthworms”. The preparation for this treatment was as follows: take ½ lb (0.2 kg) of earth-worms, 2 lb (0.9 kg) of olive oil and 2 oz (57g) of wine and boil together until the wine has evaporated. Store for later use. Unfortunately, the recipe does not state if the worms were to be alive or dead. According to the pharmacists of the day, oil of earthworm was a pain reliever, especially for aching joints, and was also recommended for arthritis, rickets and cramp. The oil was probably rubbed on to the skin. However, one writer gives a warning saying “But they who trust much to it…will be disappointed”. The religious figure at the bottom is probably St Ignatius of Loyola (1491- 1556), the founder of the Society of Jesus, whose members are known as Jesuits. The letters IHS are the first three letters from the Greek name for Jesus. Unknown maker, Italy, 1731-1770
Card advertising Kimball's Anti-Rheumatic Ring. 'A Speedy and Permanent Cure for: Rheumatism, Neuralgia, Gout, Sciatica, Lumbago etc'. 1900s
A man representing the remedy Finidol rescues another man from the clutches of an octopus whose tentacles represent rheumatic and arthritic diseases. Colour lithograph after René Vincent.
Clarke’s Blood Mixture was advertised as a treatment for a number of skin and blood diseases, including gout, rheumatism, scrofula, eczema and scurvy. In 1909, the British Medical Association estimated the cost of its ingredients was the equivalent of half a penny (at today’s prices) compared to the sales cost, which was 14 pence in modern terms. The maker, Lincoln Midland Counties Drug Co, claimed all skin and blood diseases “can only be cured by purifying the blood”. The advert shows a picture of the packaging so customers knew which preparation was the genuine article. The advert claimed that the preparation had stood the test of time for fifty years – the treatment was available in the United Kingdom until 1968, although the original recipe had been altered. maker: Unknown maker Place made: United Kingdom
Baldwin's Herbal Tonic Mixture. Nature's general restorer of the system and purifier of the blood. Printed in bold black display type. Bears quotation: "The Lord causeth the grass to grow for the cattle, and the herbs for the use of man" Psalm CIV, 14
Rheumatism patient uses electrical machine called the Galvanoset which forces the drug through the flesh by electrical means, 1925.
Oil of Foxes (Oglio di Volpine) was prepared by gutting a whole fox before simmering it in spring water, sea water, oil and salt until the water evaporated. The cooked fox was then boiled in water infused with herbs, and the water strained and stored for use. Oil of Foxes was thought useful for treating gout and aching joints. It is shown here with three similar oils made from animals. Only Oil of Foxes had universal approval from medical and pharmacy texts. maker: Unknown maker Place made: Veneto, Italy