Ann Rheum Dis：日光浴或预防类风湿关节炎

　　美国学者2月8日于《风湿病年鉴》（Ann Rheum Dis）在线发表了护士健康研究（NHS）和NHSⅡ结果。

　　NHS提示，暴露于环境中紫外线B（UV-B）与类风湿关节炎风险降低相关；但NHSⅡ未发现这种相关性。

　　年轻一代更多使用防晒品可能是导致上述差异的原因。

Exposure to ultraviolet-B and risk of developing rheumatoid arthritis among women in the Nurses’ Health Study

Objective 

To examine the association between ultraviolet-B (UV-B) light exposure and rheumatoid arthritis (RA) risk among women in two large prospective cohort studies, the Nurses’ Health Study (NHS) and the Nurses’ Health Study II (NHSII).

Methods 

A total of 106 368 women from NHS, aged 30–55 years in 1976, and 115 561 women from NHSII, aged 25–42 in 1989, were included in the analysis. We identified women with incident RA from the start of each cohort until 2008 (NHS) and 2009 (NHSII). Cumulative average UV-B flux, a composite measure of ambient UV exposure based on latitude, altitude and cloud cover, was estimated according to state of residence and categorised as low, medium or high. Estimates of UV-B at birth and age 15 years were also examined. We used multivariable-adjusted Cox proportional hazards models to estimate HR and 95% CI.

Results 

1314 incident RA cases were identified in total. Among NHS participants, higher cumulative average UV-B exposure was associated with decreased RA risk; those in the highest versus lowest category had a 21% decreased RA risk (HR (95% CI); 0.79 (0.66 to 0.94)). UV-B was not associated with RA risk among younger women in NHSII (1.12 (0.87 to 1.44)). Results were similar for UV-B at birth and at age 15.

Conclusions 

These results suggest that ambient UV-B exposure is associated with a lower RA risk in NHS, but not NHSII. Differences in sun-protective behaviours (eg, greater use of sun block in younger generations) may explain the disparate results.