Ann Rheum Dis 71:1370-1373 doi:10.1136/annrheumdis-2011-201208
  • Clinical and epidemiological research
  • Concise report

Does the change in season affect disease activity in patients with psoriatic arthritis?

  1. Dafna D Gladman
  1. Psoriatic Arthritis Clinic, Centre for Prognostic Studies in the Rheumatic Diseases, Toronto Western Hospital, University of Toronto, Toronto Western Research Institute, Toronto, Canada
  1. Correspondence to Dafna D Gladman, Centre for Prognosis Studies in the Rheumatic Diseases, Toronto Western Hospital, Room 1E-409, 399 Bathurst Street, Toronto, ON M5T 2S8, Canada; dafna.gladman{at}
  1. Contributors All authors were involved in drafting the article or revising it critically for important intellectual content, and all authors approved the final version to be published. All authors were likewise involved in the study conception and design, acquisition of data and analysis and interpretation of data. DDG had full access to all the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis.

  • Accepted 26 February 2012
  • Published Online First 13 April 2012


Objectives To determine whether there is seasonal variation in disease activity of patients with psoriatic arthritis (PsA).

Methods The authors identified the first available set of consecutive summer and winter visits for every patient from the prospective cohort of PsA. Comparison between summer and winter visits, and comparison of the repeated summer/winter visits, from 1978 until 2011 for the same identified patients was conducted for demographics, disease activity outcomes, laboratory results and treatment. The authors categorised disease activity into high, moderate and low states, and improvement versus flare/worsening. Descriptive statistics were computed and multivariate analyses using logistic regression and generalised estimating equations were conducted.

Results The first available summer and winter visit were identified for 253 patients, and 1789 observations were analysed. There was no statistically significant difference in patients' demographics, disease activity outcomes, laboratory results and treatment between summer and winter visits. Bath Ankylosing Spondylitis Disease Activity Index scores were greater for summer visits and patients graded their disease as being worse in winter as compared with summer in the univariate analysis, but this difference did not hold in the multivariate analysis.

Conclusions The change in season does not affect PsA patients' characteristics and disease activity outcomes as determined by the physicians and patients.


  • Competing interests None.

  • Ethics approval Research Ethics Board, University Health Network, University of Toronto.

  • Provenance and peer review Not commissioned; externally peer reviewed.