The Jamaican Autism study is a NIH-supported age- and sex-matched case–control study that began enrollment of Jamaican children 2–8 years of age in December 2009, investigating whether environmental exposures to several heavy metals, including mercury, have a role in the onset of an ASD. Information regarding the recruitment and assessment of ASD cases and controls has been described previously (Rahbar etal. 2012 (link)). In short, we administered the Autism Diagnostic Observation Schedule (ADOS) (Lord et al. 2002 ) and the Autism Diagnostic Interview-Revised (ADI-R) (Rutter et al. 2003 ) to confirm the diagnosis of an ASD in case children. As the ADOS and ADI-R assessments take a considerable amount of time (Dixon et al. 2009 ), and we wished to reduce any undue burden on potential control children and their parents, we instead administered the Lifetime form of the Social Communication Questionnaire (SCQ) (Rutter et al. 2003 ) to the parents/guardians of control children to rule out symptoms of ASDs.
We also administered a pre-tested questionnaire to the parents/guardians of both cases and controls to collect demographic and socioeconomic (SES) information (e.g., ownership of a car by the family), parental levels of education, medication and immunization history of children, and potential exposure to mercury through food, with a particular focus on the types and amount of seafood consumed by children. The types of seafood considered included salt water fish, fresh water fish (pond fish, tilapia), sardine or mackerel (canned fish), tuna (canned fish), salt fish (pickled mackerel), shellfish (lobsters, crabs), and shrimp. The frequency of seafood consumption by children was measured through the number of servings (number of meals) of seafood consumed per week. At the end of each interview, the UWI project coordinator, who has received phlebotomy training, collected about 2 mL of venous whole blood from each child using stainless steel needles into plastic tubes containing EDTA which were prescreened for mercury, cadmium, and lead. We also collected hair samples (only from children with long hair, at least 3 in). The blood samples were frozen and stored at −20 °C until they were transported to the Michigan Department of Community Health (MDCH) Trace Metals Lab at ambient temperature on ice packs for trace metal analyses, including mercury.
All participating parents provided written informed consent. In addition, this study was approved by the Institutional Review Boards of the University of Texas Health Science Center at Houston (UTHealth) and the University of the West Indies in Kingston, Jamaica. The data presented herein represent an analysis of 65 matched case–control pairs. As shown below, the available data provide sufficient power to detect meaningful effect sizes for continuous variables, such as blood mercury concentrations, between any two groups compared (e.g., ASD cases and controls or those who eat or do not eat seafood).
We also administered a pre-tested questionnaire to the parents/guardians of both cases and controls to collect demographic and socioeconomic (SES) information (e.g., ownership of a car by the family), parental levels of education, medication and immunization history of children, and potential exposure to mercury through food, with a particular focus on the types and amount of seafood consumed by children. The types of seafood considered included salt water fish, fresh water fish (pond fish, tilapia), sardine or mackerel (canned fish), tuna (canned fish), salt fish (pickled mackerel), shellfish (lobsters, crabs), and shrimp. The frequency of seafood consumption by children was measured through the number of servings (number of meals) of seafood consumed per week. At the end of each interview, the UWI project coordinator, who has received phlebotomy training, collected about 2 mL of venous whole blood from each child using stainless steel needles into plastic tubes containing EDTA which were prescreened for mercury, cadmium, and lead. We also collected hair samples (only from children with long hair, at least 3 in). The blood samples were frozen and stored at −20 °C until they were transported to the Michigan Department of Community Health (MDCH) Trace Metals Lab at ambient temperature on ice packs for trace metal analyses, including mercury.
All participating parents provided written informed consent. In addition, this study was approved by the Institutional Review Boards of the University of Texas Health Science Center at Houston (UTHealth) and the University of the West Indies in Kingston, Jamaica. The data presented herein represent an analysis of 65 matched case–control pairs. As shown below, the available data provide sufficient power to detect meaningful effect sizes for continuous variables, such as blood mercury concentrations, between any two groups compared (e.g., ASD cases and controls or those who eat or do not eat seafood).
