ARD：紫外线暴露可减少女性罹患类风湿关节炎风险

类风湿关节炎的发病与基因及环境因素相关。既往研究发现，美国北部人群的RA风险较高，这可能与较低的紫外线（UV）暴露有关。来自哈佛大学公共卫生学院流行病学系的Elizabeth V Arkema等研究者通过护士健康研究（NHS）和护士健康研究Ⅱ（NHSⅡ）两个大型前瞻性队列研究，评估了女性暴露于紫外线-B（UV-B）与其罹患类风湿关节炎（RA）风险之间的相关性。研究结果发表于2013年4月的《风湿病学年鉴》（Ann Rheum Dis）杂志上。研究认为，环境UV-B暴露量增加与RA发病风险较低存在相关性。
作者从NHS研究中纳入了106368例年龄范围在30-55岁（截止至1976年）的女性，同时从NHSⅡ研究中纳入了115561例年龄范围在25-42岁（截止至1989年）的女性。研究者对这两项队列研究所纳入的病例，自研究开始之时起，分别随访至2008年（NHS）和2009年（NHSⅡ），确认了在随访期中罹患RA的病例数。根据累积平均UV-B照射量，以及基于各州纬度、海拔及云量的差异进行混合测定所得出的环境UV暴露量，将所纳入病例的紫外线暴露量分为低中高三个组。同时，研究者还评估了纳入病例在出生时和15岁时接受的UV-B照射量。研究者采用多变量调整COX比例危险度模型评估各组数据的HR和95%CI。
研究共确认了1314例RA病例。研究者在NHS研究的参与者中发现，较高的累积平均UV-B暴露量与RA风险降低之间存在相关性；高剂量组患者较低剂量组患者罹患RA的风险下降了21%【HR（95%CI）；0.79（0.66-0.94）】。在NHSⅡ研究中，年轻女性罹患RA的风险与UV-B之间没有明确相关性【1.12（0.87-1.44）】。在评估病例出生时和15岁时UV-B照射量的研究中也得出类似的结果。
上述研究结果表明，在NHS研究中，环境UV-B暴露量增加与较低的RA发病风险存在相关性，但NHSⅡ研究则无此表现。防晒行为的差异（如年轻时更常使用防晒霜）可能可以解释两个研究结果有所差异的原因。
与类风湿关节炎相关的拓展阅读：

• Ann Rheum Dis：日光浴或预防类风湿关节炎
• Rheumatology：类风湿关节炎患者整体肿瘤罹患风险高
• Lancet：依那西普维持治疗可控制类风湿关节炎疾病活动
• Arthritis Rheum：类风湿关节炎患者 THA后易脱臼，TKA后易感染
• FDA批准第一个治疗类风湿关节炎口服生物制剂Xeljanz
• Arthritis Rheum：类风湿关节炎患者牙周炎高发
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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.