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Analysis of Self‐selection Bias in a Population‐based Cohort Study of Autism Spectrum Disorders
Author(s) -
Nilsen Roy M.,
Surén Pål,
Gunnes Nina,
Alsaker Elin R.,
Bresnahan Michaeline,
Hirtz Deborah,
Hornig Mady,
Lie Kari Kveim,
Lipkin W. Ian,
ReichbornKjennerud Ted,
Roth Christine,
Schjølberg Synnve,
Davey Smith George,
Susser Ezra,
Vollset Stein Emil,
Øyen AnneSiri,
Magnus Per,
Stoltenberg Camilla
Publication year - 2013
Publication title -
paediatric and perinatal epidemiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.667
H-Index - 88
eISSN - 1365-3016
pISSN - 0269-5022
DOI - 10.1111/ppe.12077
Subject(s) - medicine , cohort , population , pregnancy , obstetrics , cohort study , odds ratio , caesarean section , prospective cohort study , pediatrics , prenatal care , environmental health , genetics , biology
Background This study examined potential self‐selection bias in a large pregnancy cohort by comparing exposure‐outcome associations from the cohort to similar associations obtained from nationwide registry data. The outcome under study was specialist‐confirmed diagnosis of autism spectrum disorders ( ASD s). Methods The cohort sample ( n = 89 836) was derived from the population‐based prospective N orwegian M other and C hild C ohort S tudy and its substudy of ASD s, the A utism B irth C ohort ( ABC ) study. The nationwide registry data were derived from the M edical B irth R egistry of N orway ( n = 507 856). The children were born in 1999–2007, and seven prenatal and perinatal exposures were selected for analyses. Results ASD s were reported for 234 (0.26%) children in the cohort and 2072 (0.41%) in the nationwide population. Compared with the nationwide population, the cohort had an under‐representation of the youngest women (<25 years), those who had single status, mothers who smoked during pregnancy, and non‐users of prenatal folic acid supplements. The ratios of the adjusted odds ratios ( OR s) in the cohort over the adjusted OR s in the nationwide population were as follows; primipara pregnancy: 1.39/1.22, prenatal folic acid use: 0.85/0.86, prenatal smoking: 1.20/1.17, preterm birth (<37 weeks): 1.48/1.42, low birthweight (<2500 g): 1.60/1.58, male sex: 4.39/4.59 (unadjusted only); and caesarean section history: 1.03/1.04. Conclusions Associations estimated between ASD s and perinatal and prenatal exposures in the cohort are close to those estimated in the nationwide population. Self‐selection does not appear to compromise validity of exposure‐outcome associations in the ABC study.