Impact of Season, Environmental Temperature, and Humidity on Raynaud Phenomenon in an Australian Systemic Sclerosis Cohort.

Objective: The aim of this study was to determine the impact of season, temperature and humidity on the severity of Raynaud phenomenon (RP) in systemic sclerosis.

Methods: Data from the Australian Scleroderma Cohort Study were used to assess associations of patient-reported worsened RP in the month preceding each study visit. Mean monthly weather data were obtained from the closest weather station to the patient's address. We evaluated the relationship between worsened RP and health-related quality of life (HRQoL) measured using the Short Form 36 instrument.

Results: Among 1,972 patients with systemic sclerosis, RP was a near-universal finding, and worsened RP in the preceding month was reported in 26.7% of 9,175 visits. "Worsened RP" showed significant environmental variability. On multivariable analysis, worsened RP was associated with low mean maximum temperatures (odds ratio [OR] 0.91, 95% confidence interval [95% CI] 0.90-0.92, P < 0.001), high relative humidity (OR 1.05, 95% CI 1.04-1.05, P < 0.001) and lower mean daily evaporation (OR 0.77, 95% CI 0.73-0.81, P < 0.001). Worsened RP was strongly associated with telangiectasia, calcinosis, and digital ulceration, as well as demonstrating an association with anticentromere antibody and gastroesophageal reflux disease and a negative correlation with diffuse disease. Worsened RP was also strongly associated with worse HRQoL.

Conclusion: Lower environmental temperature and higher relative humidity had significant associations with worsened RP in this systemic sclerosis cohort, suggesting an important role for dry warmth in managing this condition.