A retrospective case study of 420 respondents with psoriasis from a 2005 telephone and email survey was conducted. Its aim was to study which factors were predictors of sleep disturbance within the last month. The following factors, with odds ratios (ORs), were identified as predictors of sleep disturbance: psoriatic arthritis (OR: 3.26; p < 0.001); itch (OR: 1.24; p < 0.001), pain of lesions (OR: 1.12; p = 0.045) and impact of emotional well-being (OR: 1.19; p = 0.030). Nearly half of all respondents reported sleep disturbances which impacted as few as 1-2 nights/month or as many as >15 nights/month. Psoriatic arthritis would seem to be the strongest predictor of sleep ...