Abstract
BackgroundStudying second-generation immigrants can help in identifying genetic or environmental risk factors for childhood autism. Most previous studies have focused on maternal region of birth and showed inconsistent results. No previous study has been conducted in Finland.MethodsThe study was a nested case–control study based on a national birth cohort. Children born in 1987–2005 and diagnosed with childhood autism by the year 2007 were identified from the Finnish Hospital Discharge Register. Controls were selected from the Finnish Medical Birth Register. Information on maternal and paternal country of birth and mother tongue was collected from the Finnish Central Population Register. There were 1132 cases and 4515 matched controls. The statistical test used was conditional logistic regression analysis.ResultsCompared with children with two Finnish parents, the risk of childhood autism was increased for those whose parents are both immigrants (adjusted odds ratio [aOR] 1.8, 95% confidence interval [CI] 1.2–2.7) and for those with only an immigrant mother (aOR 1.8, 95% CI 1.2–2.7), but not for those with only an immigrant father. The risk was increased for those with a mother born in the former Soviet Union or Yugoslavia and for those with a mother or a father born in Asia. Specific parental countries of birth associated with an increased risk were the former Soviet Union, the former Yugoslavia and Vietnam.ConclusionsIn Finland, children who are born to immigrant mothers with or without an immigrant partner, have an increased risk of childhood autism. The risk varies with immigrant parents’ region of birth. The findings may help in identifying possible risk factors, which can be examined in future studies.
Highlights
Studying second-generation immigrants can help in identifying genetic or environmental risk factors for childhood autism
Second-generation immigrants are an important group for studying the etiology of childhood autism, because parents from different regions may differ in terms of genetic risk, but they may have been exposed to different levels of environmental risk factors before or after immigration
The study is derived from the Finnish Prenatal Study of Autism (FIPS-A), which is a nested case–control study based on a national birth cohort, and aims to identify early life risk factors of Autism spectrum disorders (ASD)
Summary
Studying second-generation immigrants can help in identifying genetic or environmental risk factors for childhood autism. Many previous studies conducted in Europe have shown that immigrant mothers born outside Europe have an increased risk of having a child with childhood autism [9,10,11] or other ASD [12], but there are studies reporting a non-significant association [13,14]. A California study showed no increased risk for any immigrant mothers, Mexican-born mothers had a decreased risk of having a child with childhood autism [17]. Two studies have shown an association between father’s, but not mother’s immigrant background, and childhood autism [13] or ASD [14] in offspring. One study has shown an association between mother’s, but not father’s immigrant background, and childhood autism [18]. It has been shown that having only an immigrant mother [10,11] or two immigrant parents [10] is associated with childhood autism, but having only an immigrant father is not
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