Camilla B Jensen1, Michael Gamborg2, Kyle Raymond2, John McGrath3, Thorkild I A Sørensen4, Berit L Heitmann5. 1. Institute of Preventive Medicine, Bispebjerg and Frederiksberg Hospital, The Capital Region, Copenhagen, Denmark; Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark. Electronic address: Camilla.bjoern.jensen@regionh.dk. 2. Institute of Preventive Medicine, Bispebjerg and Frederiksberg Hospital, The Capital Region, Copenhagen, Denmark. 3. Queensland Brain Institute, The University of Queensland, Brisbane, QLD, Australia; Queensland Centre for Mental Health Research, Brisbane, QLD, Australia. 4. Institute of Preventive Medicine, Bispebjerg and Frederiksberg Hospital, The Capital Region, Copenhagen, Denmark; Novo Nordisk Foundation Center for Basic Metabolic Research, Faculty of Health and Medical Sciences, University of Copenhagen, Denmark; MRC Integrative Epidemiology Unit, University of Bristol, Bristol, UK. 5. Institute of Preventive Medicine, Bispebjerg and Frederiksberg Hospital, The Capital Region, Copenhagen, Denmark; The Boden Institute of Obesity, Nutrition, Exercise & Eating Disorders, University of Sydney, Australia; National Institute of Public Health, University of Southern Denmark, Denmark.
Abstract
BACKGROUND: Many environmental factors have been shown to influence birth weight (BW) and one of these are season of birth. AIM: The aim of the present study was to investigate the seasonal variation in BW in Denmark during 1936-1989, and to see if the variation could be explained by sunshine exposure during pregnancy. METHODS: The study population was selected from the Copenhagen School Health Records Register and included 276 339 children born between 1936 and 1989. Seasonal variation was modeled using a non-stationary sinusoidal model that allowed the underlying trend in BW and the amplitude and phase of the yearly cycles to change. RESULTS: There was a clear seasonal pattern in BW which, however, changed gradually across the study period. The highest BWs were seen during fall (September - October) from 1936 to 1963, but a new peak gradually grew from the early 1940s during early summer (May - June) and became the highest from 1964 to 1989. The amplitude of the fall peak started at 25.5 (95%CI 24.6; 25.9) grams and gradually disappeared. The amplitude of the early summer peak gradually arose from nothing to a peak of 18.6 (95%CI 17.7; 19.6) grams in the mid 1980s where it started to decrease again. Sunshine did not explain the seasonal variation in BW. CONCLUSION: There was a clear seasonal pattern in BW in Denmark 1936-1989, which however changed across the study period. Throughout the study period we observed a peak in BW during the fall, but gradually, starting in the early 1940s, an additional early summer peak emerged and became the highest from 1964 and onwards.
BACKGROUND: Many environmental factors have been shown to influence birth weight (BW) and one of these are season of birth. AIM: The aim of the present study was to investigate the seasonal variation in BW in Denmark during 1936-1989, and to see if the variation could be explained by sunshine exposure during pregnancy. METHODS: The study population was selected from the Copenhagen School Health Records Register and included 276 339 children born between 1936 and 1989. Seasonal variation was modeled using a non-stationary sinusoidal model that allowed the underlying trend in BW and the amplitude and phase of the yearly cycles to change. RESULTS: There was a clear seasonal pattern in BW which, however, changed gradually across the study period. The highest BWs were seen during fall (September - October) from 1936 to 1963, but a new peak gradually grew from the early 1940s during early summer (May - June) and became the highest from 1964 to 1989. The amplitude of the fall peak started at 25.5 (95%CI 24.6; 25.9) grams and gradually disappeared. The amplitude of the early summer peak gradually arose from nothing to a peak of 18.6 (95%CI 17.7; 19.6) grams in the mid 1980s where it started to decrease again. Sunshine did not explain the seasonal variation in BW. CONCLUSION: There was a clear seasonal pattern in BW in Denmark 1936-1989, which however changed across the study period. Throughout the study period we observed a peak in BW during the fall, but gradually, starting in the early 1940s, an additional early summer peak emerged and became the highest from 1964 and onwards.
Authors: Camilla B Jensen; Esther Zimmermann; Michael Gamborg; Berit L Heitmann; Jennifer L Baker; Allan Vaag; Thorkild I A Sørensen Journal: Diabetologia Date: 2015-06-16 Impact factor: 10.122
Authors: Samantha M Garay; Katrina A Savory; Lorna A Sumption; Richard J A Penketh; Ian R Jones; Anna B Janssen; Rosalind M John Journal: Psychoneuroendocrinology Date: 2019-05-31 Impact factor: 4.905