Abstract
BackgroundPrevious studies suggest that RA activity is sensitive to seasonal changes. This study explored the influence of season on RA activity, particularly the distribution of affected joints, using a nationwide database in Japan.MethodsWe investigated 12,839 patients whose RA activity was recorded in spring (n = 3250), summer (n = 916), fall (n = 1021), and winter (n = 7652). Disease activity score (DAS) 28-CRP, simplified disease activity index (SDAI), and clinical disease activity index (CDAI) were used as indices of disease activity. Disease activity was also assessed according to DAS28-CRP scores (remission, low, moderate, or high). The affected joint distribution was investigated using novel joint indices (x, y, z), where x and y are indices for the upper and lower joints, respectively, and z is the index for large joint predominance.ResultsMean DAS28-CRP and median SDAI and CDAI scores were highest in spring and lowest in fall. There was a significant difference in the DAS28-CRP for fall versus spring and winter. Fall was associated with a higher remission rate, and spring and winter with high and moderate RA activity, respectively. Significant differences in x, y, SDAI, and CDAI scores were found for spring versus summer, fall, and winter, in addition to fall versus winter (except in y). There was no seasonal difference in the z index.ConclusionsRA activity in the upper and lower extremities may be highest in spring, followed by winter. Seasonal changes should be considered in patients with RA to better understand their symptoms.
Highlights
Previous studies suggest that Rheumatoid arthritis (RA) activity is sensitive to seasonal changes
Data on tender joint count (TJC), swollen joint count (SJC), visual analog scale (VAS) pain score, PtGA, physician’s global assessment of disease activity (PhGA), C-reactive protein (CRP), disease stage, and functional class were available for 12,839 patients with RA registered in NinJa2016
Post hoc analysis revealed that the disease duration was significantly longer in RA patients evaluated in fall than in those evaluated in winter (p < 0.05) and that the proportion of patients with class 3–4 functional status was significantly lower in patients evaluated in fall (p < 0.01) and higher in those evaluated in winter (p < 0.05)
Summary
Previous studies suggest that RA activity is sensitive to seasonal changes. This study explored the influence of season on RA activity, the distribution of affected joints, using a nationwide database in Japan. Patberg et al reviewed the literature on meteorological conditions [1] and found a significant relationship between weather and RA activity in 11 reports [2,3,4,5,6,7,8,9,10,11,12], indicating an important association of humidity with signs and symptoms of RA. In many parts of the world, the year is divided into four 3-month seasons (winter, spring, summer, and fall) that are characterized by specific weather conditions (temperature, atmospheric pressure, humidity, and precipitation) and hours of daylight [26]. The onset of symptoms of arthritis during winter or spring was reported to be associated with more radiographic joint damage after 6
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