Seasonal Effects on Hospitalizations Due to Mood and Psychotic Disorders: A Nationwide 31-Year Register Study

• Main Authors: Törmälehto S, Svirskis T, Partonen T, Isometsä E, Pirkola S, Virtanen M, Sund R
• Format: Article in Journal/Newspaper
• Language: English
• Published: Dove Medical Press 2022
• Subjects: seasonal variation; photoperiod; hospital admission; mood disorders; bipolar disorder; schizophrenia; Infectious and parasitic diseases; RC109-216; sami
• Online Access: https://doaj.org/article/bf1cdcc774bc4d34a1effe83ca9d0d48

Soili Törmälehto,1 Tanja Svirskis,2 Timo Partonen,3 Erkki Isometsä,2 Sami Pirkola,4 Marianna Virtanen,1,5 Reijo Sund6 1School of Educational Sciences and Psychology, University of Eastern Finland, Joensuu, Finland; 2Department of Psychiatry, University of Helsinki and Helsinki University Hospital, Helsinki, Finland; 3Department of Public Health and Welfare, Finnish Institute for Health and Welfare, Helsinki, Finland; 4Faculty of Social Sciences, University of Tampere and Pirkanmaa Hospital District, Tampere, Finland; 5Division of Insurance Medicine, Department of Clinical Neuroscience, Karolinska Institutet, Stockholm, Sweden; 6Institute of Clinical Medicine, University of Eastern Finland, Kuopio, FinlandCorrespondence: Soili Törmälehto, School of Educational Sciences and Psychology C/O Institute of Clinical Medicine, University of Eastern Finland, P.O. Box 1627, Kuopio, FI-70211, Finland, Email [e-mail]: To examine seasonal patterns of hospital admissions due to mood and psychotic disorders and to investigate whether the admission rates show variation according to the seasonal daylength (photoperiods).Patients and Methods: A retrospective nationwide register-based cohort of all psychiatric admissions (N=978,079) during 1987– 2017 in Finland was utilized. The smoothed time-series of adjusted ratio of observed and expected (O/E) daily counts were estimated to examine seasonal variation. The mean O/E with 95% confidence intervals (CI) was used to study the admission rates by photoperiods. The calendar days were classified into the 71-day photoperiods based on the daylength (long/summer, short/winter, equal/spring, equal/fall) and the pace of change in daylength (slowly/rapidly increasing/decreasing daylength).Results: Manic episodes peaked in summer during the long (mean O/E=1.10, 95% CI=1.06– 1.13) and slowly decreasing (1.09, 1.06– 1.13) photoperiods and had a nadir in winter during the slowly increasing (0.93, 0.89– 0.98) photoperiod. Admissions for unipolar depressive (UPD) episodes ...