Abstract
IntroductionBipolar disorder varies with season: admissions for depression peak in winter and mania peak in summer. Sunlight presumably increases the risk of mania through suppression of melatonin. If so, we expect admissions for mania to vary in accordance with climate variations.ObjectivesTo investigate how climate and climate changes affects admissions for mania.AimsTo identify which climate variables – sunshine, ultraviolet radiation, rain and snow cover – affect admissions for mania.To examine whether year-to-year weather variation as well as long-term climate changes reflects the variation in number of admissions for mania.MethodsThis register-based nationwide cohort study covers all patients admitted for mania (ICD-10 code F31 or F30.0–F30.2) between 1995 and 2012 in Denmark. Climate data, obtained from the Danish Meteorological Institute, were merged with admission data and correlated using an Unobserved Component Model regression model.Preliminary resultsIn total, 8893 patients were admitted 24,313 times between 1995 and 2012: 6573 first-admissions and 17,740 readmissions. Linear regression shows significant association between admissions per day and hours of sunshine (P < 0.01) and ultraviolet radiation (UV) dose (P < 0.01). Average days with snow cover and rain were not significantly correlated with admissions. Analyses on year-to-year variation and long-term change are not yet available.Preliminary conclusionsAdmissions for mania are correlated with sunshine and UV, but not rain and snow cover. If more patients are admitted during very sunny summers compared with less sunny summers this implies a relation with light itself and not just season.Disclosure of interestThe authors have not supplied their declaration of competing interest.
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