The 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 in systemic sclerosis.

Methods: Data from the Australian Scleroderma Cohort Study were utilised 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 SF-36 instrument.

Results: Among 1972 systemic sclerosis patients, RP was a near universal finding, and worsened RP in the preceding month was reported in 26.7% of 9175 visits. 'Worsened RP' showed significant environmental variability. On multivariable analysis, worsened RP was associated with low mean maximum temperatures (OR 0.91, 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 (DU), as well as demonstrating an association with anti-centromere antibody and gastro-oesophageal reflux disease (GORD) 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.