BACKGROUND: Patient-reported triggers for atopic dermatitis (AD) flares include changes in ultraviolet irradiation, humidity and temperature.

OBJECTIVES: To identify the relationships between weather data and healthcare utilization in AD patients.

METHODS: Using nationwide healthcare registries, clinic (1994-2012) and hospital visits (1977-2012) for AD treatment were calculated as well as monthly totals of topical corticosteroid (TCS) (1996-2012) and calcineurin inhibitor (TCI) prescriptions (2003-20012) filled by AD patients. We calculated monthly averages of temperature, atmospheric pressure, cloud cover and hours of bright sunlight and compared these variables to healthcare utilization endpoints, for the years 2000-2012 (n = 156 months), using linear regression models.

RESULTS: In Denmark, between the year 2000 and 2012, mean monthly totals of AD emergency room visits were 6, AD hospitalizations 32, AD outpatient visits 170, TCS prescriptions filled by AD patients 3811 and TCI prescriptions 2552. Healthcare utilization among AD patients was highest in winter/spring. Temperature was the environmental variable that had the strongest association with healthcare utilization: per 1°C lower monthly temperature, 2 more (95% confidence interval [CI] 1-4) AD clinic/hospital visits hospitalizations were observed, 18 (95% CI 9-26) more TCS prescriptions and 53 (95% CI 36-70) more TCI prescriptions were filled by patients with AD. Environmental variables were highly correlated. Associations between AD healthcare utilization and hours of cloud cover were generally positive, while those with hours of bright sunlight were generally inverse.

CONCLUSIONS: AD healthcare utilization markers changed significantly with season. A decline in temperature correlated well with AD patients' healthcare utilization, but a causative role could not be determined with certainty.