Background/Purpose: To evaluate whether meteorological parameters influence pain and disease activity in patients with rheumatoid arthritis (RA).

Methods: We assessed correlations between individual meteorological variables and clinical measures of disease activity: clinical disease activity index (CDAI), self-reported pain (by visual analogue scale), tender- and swollen 28 joint counts (TJC and SJC) and patient global assessment (PGA). Assessments documented in our RA database as well as the average temperature and relative humidity, obtained from the Central Institute for Meteorology and Geodynamics, were matched on a daily basis for a period of 10 years between 2005 and 2015, and analyzed using generalized estimating equations (longitudinal data analysis). On average, an individual patient would have 3-monthly visits throughout this observation time.

Results: A total of 1437 patients with RA (average disease duration at first visit: 4.88±8.63 years; 77% female, mean CDAI 17.8±11.7,) were analyzed. Higher temperature and lower humidity were significantly associated with lower CDAI (p=0.0002, and p=0.0332, respectively). Both, temperature and humidity were significantly associated with pain (p=0.0076), PGA (p=0.0011), and SJC (p=0.0187). Temperature and humidity showed an interaction on pain: lower temperatures were associated with higher pain levels at the lower quartiles of humidity; in contrast, lower temperature corresponded to lower pain levels at the highest quartile of humidity (Figure 1).

Conclusion: In this largest association study of meteorological parameters with RA specific outcomes both temperature and relative humidity were shown to have significant effects on disease activity. Individual measures of disease activity and pain correlated either with temperature or humidity, while the composite CDAI measure correlated with both meteorological variables. These data are confirmatory of the influence of the climate environment on outcomes of an inflammatory disease.