title: Month and Season of Birth as a Risk Factor for Alzheimer's Disease: A Nationwide Nested Case-control Study.
abstract: OBJECTIVE
  Season of birth, an exogenous indicator of early life environment, has been related to higher risk of adverse psychiatric outcomes but the findings for Alzheimer's disease (AD) have been inconsistent. We investigated whether the month or season of birth are associated with AD.
  
  
  METHODS
  A nationwide nested case-control study including all community-dwellers with clinically verified AD diagnosed in 2005 to 2012 (n=70 719) and up to four age- sex- and region of residence-matched controls (n=282 862) residing in Finland. Associations between month and season of birth and AD were studied with conditional logistic regression.
  
  
  RESULTS
  Month of birth was not associated with AD (p=0.09). No strong associations were observed with season (p=0.13), although in comparison to winter births (December-February) summer births (June-August) were associated with higher odds of AD (odds ratio, 1.03; 95% confidence interval, 1.00 to 1.05). However, the absolute difference in prevalence in winter births was only 0.5% (prevalence of those born in winter were 31.7% and 32.2% for cases and controls, respectively).
  
  
  CONCLUSIONS
  Although our findings do not support the hypothesis that season of birth is related to AD/dementia risk, they do not invalidate the developmental origins of health and disease hypothesis in late-life cognition. It is possible that season does not adequately capture the early life circumstances, or that other (postnatal) risk factors such as lifestyle or socioeconomic factors overrule the impact of prenatal and perinatal factors.
authors.affiliation: School of Pharmacy, University of Eastern Finland, Kuopio, Finland.|Research Center for Comparative Effectiveness and Patient Safety, University of Eastern Finland, Kuopio, Finland.
authors.forename: Anna-Maija
authors.identifier: 0000-0001-9270-9268
authors.initials: AM
authors.lastname: Tolppanen
authors.affiliation: School of Pharmacy, University of Eastern Finland, Kuopio, Finland.
authors.forename: Riitta
authors.initials: R
authors.lastname: Ahonen
authors.affiliation: School of Pharmacy, University of Eastern Finland, Kuopio, Finland.|Kuopio Research Center of Geriatric Care, School of Pharmacy, University of Eastern Finland, Kuopio, Finland.
authors.forename: Marjaana
authors.initials: M
authors.lastname: Koponen
authors.affiliation: School of Pharmacy, University of Eastern Finland, Kuopio, Finland.|Kuopio Research Center of Geriatric Care, School of Pharmacy, University of Eastern Finland, Kuopio, Finland.
authors.forename: Piia
authors.initials: P
authors.lastname: Lavikainen
authors.affiliation: Department of Psychiatry, Kuopio University Hospital, Kuopio, Finland.
authors.forename: Maija
authors.initials: M
authors.lastname: Purhonen
authors.affiliation: School of Pharmacy, University of Eastern Finland, Kuopio, Finland.|Kuopio Research Center of Geriatric Care, School of Pharmacy, University of Eastern Finland, Kuopio, Finland.
authors.forename: Heidi
authors.initials: H
authors.lastname: Taipale
authors.affiliation: Department of Forensic Psychiatry, Niuvanniemi Hospital, University of Eastern Finland, Kuopio, Finland.|Department of Clinical Neuroscience, Karolinska Institutet, Stockholm, Sweden.|National Institute for Health and Welfare, Helsinki, Finland.
authors.forename: Antti
authors.initials: A
authors.lastname: Tanskanen
authors.affiliation: Department of Forensic Psychiatry, Niuvanniemi Hospital, University of Eastern Finland, Kuopio, Finland.|Department of Clinical Neuroscience, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Jari
authors.identifier: 0000-0002-0400-6798
authors.initials: J
authors.lastname: Tiihonen
authors.affiliation: School of Pharmacy, University of Eastern Finland, Kuopio, Finland.|Kuopio Research Center of Geriatric Care, School of Pharmacy, University of Eastern Finland, Kuopio, Finland.
authors.forename: Miia
authors.initials: M
authors.lastname: Tiihonen
authors.affiliation: School of Pharmacy, University of Eastern Finland, Kuopio, Finland.|Kuopio Research Center of Geriatric Care, School of Pharmacy, University of Eastern Finland, Kuopio, Finland.
authors.forename: Sirpa
authors.initials: S
authors.lastname: Hartikainen
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000544:Alzheimer Disease / Q000175:diagnosis* / Q000453:epidemiology; D016022:Case-Control Studies; D005387:Finland; D006801:Humans; D016015:Logistic Models; D008875:Middle Aged; D016017:Odds Ratio; D012307:Risk Factors; D012621:Seasons
keywords: Alzheimer disease; Case-control studies; Risk factors; Seasons