Can active sun exposure decrease the risk of giant cell arteritis and polymyalgia rheumatica in women?

Acknowledgements: We acknowledge the late Håkan Olsson, who co-initiated the MISS cohort and codesigned the current study.Funder: ReumatikerförbundetLay Summary: What does this mean for patients? Polymyalgia rheumatica (PMR) is an inflammatory condition affecting older people, causing pain and stiffness of the shoulders and hips. PMR is closely linked with giant cell arteritis (GCA), a condition characterized by inflammation of the large blood vessels of the head, neck and chest. If left untreated or if treatment is delayed, GCA may lead to stroke and blindness. These conditions are more commonly seen in northern Europe and North America. Why some people develop PMR and GCA is unknown. We hypothesized that low sun exposure could increase the risk of developing PMR or GCA. To investigate this, we matched the responses of a questionnaire regarding sun exposure behaviour to electronic health records. The questionnaire was sent to almost 15 000 women living in southern Sweden. We did not see an increased risk of developing PMR or GCA in women avoiding sun exposure. Likewise, high sun exposure was not protective of PMR and GCA. The geographic variation, with PMR and GCA being more common in the northern parts of the world, may be explained by other factors. We conclude that sun exposure is likely of limited importance in why some people develop PMR or GCA