Paternal and Maternal Age Are Jointly Related to Autism Spectrum Disorders In Jamaican Children

Background: Autism Spectrum Disorders (ASDs) are complex lifelong neurodevelopmental and behavioral disorders manifesting in infancy or early childhood, characterized by impairments in social interaction and communication, and by repetitive, stereotyped behavior. ASD has become a serious public health concern with a major familial and societal economic impact. The etiology of autism is not fully understood but there is consensus among scientists that genetic factors and gene-environment interaction play a role in autism. Several studies have reported advancing parental age as a risk factor for adverse behavioral outcome during early childhood, particularly autism, yet the results remain inconsistent and the potential contribution of delayed childbearing to the increased incidence of autism has not been fully investigated. Epidemiologic data in developing countries, where the environment may be very different from that of developed countries, will broaden our understanding of the etiology of ASDs.

Objectives:  This study's primary objectives were to investigate whether environmental exposures to mercury, lead, arsenic and cadmium play a role in autism.  Additionally, we investigated other potential risk factors for autism, including maternal and paternal age.

Methods: In collaboration with the University of West Indies (UWI) in Kingston, Jamaica, we are conducting an age- and sex-matched case-control study of 150 pairs of children. We are administering the Autism Diagnostic Observation Schedule (ADOS) and the Autism Diagnostic Interview-Revised (ADI-R) to children in the UWI’s Jamaica Autism Database who have previously been identified as being at risk for ASD using the Childhood Autism Rating Scale (CARS).  For each case, an age- and sex-matched control is identified using the Social Communication Questionnaire (SCQ) to rule out symptoms of ASD.  We also administer a pre-tested questionnaire to assess demographic and socioeconomic information, parental history, and potential exposure to heavy metals through food or occupation of parents.  At the end of the interview, we collect 5 mls of whole blood, 2 mls of saliva, and hair samples to be analyzed in the US.  Conditional logistic regression and multivariate analysis are used for identifying risk factors for ASD.

Results: As of October 2010 we have enrolled 69 matched pairs. Demographic results show a study sample of 87% male with a mean age (months) of 66.41 (cases) and 67.24 (controls). About 97% of the participants are Black (African origin). Mean weight and head circumference of cases are significantly higher than those of controls (p<0.05). At birth of the index child, the mean paternal age (Mean=34.9 years, SD=8.2) and maternal age (Mean=29.4, SD=6.5) for the case population are significantly higher than that for parents of controls (p<0.05). A comparison of the joint distribution of age of the parents between the 69 matched pairs using multivariate analysis reveals a significant association between parental (paternal, maternal) age and ASD (p<0.05).

Conclusions: Although we have not yet reached our target sample size, we have gained significant insight in conducting epidemiological research on autism in other cultures. Our interim analysis of the 69 matched pairs strongly supports the joint effect (contribution) of the maternal and paternal age on ASD in offspring.