771: Maternal hypothyroidism Increases the risk of ADHD in the offspring

Abstract

To examine if maternal hypothyroidism increases the risk of attention deficit hyperactivity disorder (ADHD) in the offspring and how this risk may be modified by sex, race-ethnicity, and gestational length. A retrospective cohort study of singleton born children age 3-11 years delivered at &ge28 weeks of gestation (n=254,580) in Kaiser Permanente Southern California hospitals (2000-2013) was performed using data abstracted from the Perinatal Service System™, hospital inpatient, outpatient physician encounter, and pharmacy records. ICD-9 codes from hospitalizations during pregnancy and infant birth certificates as well as pharmacy records on medication specific for ADHD were used to ascertain the exposure and outcomes of interest. Duration of exposure was defined as time interval from first diagnosis until birth and was grouped into quartiles. Adjusted hazard ratios (HR) with 95% confidence interval (CI) were estimated to quantify potential associations between maternal hypothyroidism and child ADHD. Overall prevalence of hypothyroidism was 2%. Compared with non-ADHD children, ADHD children were more likely to be male and of White or African-American race/ethnicity. Children of women with hypothyroidism were more likely to be diagnosed with ADHD (HR 1.28, 95%CI 1.13-1.44) than offspring of undiagnosed women. A stratified analysis by duration of exposure revealed that exposure length of 2nd and 3rd quartiles were associated with significantly increased risk; 1.41-fold (95%CI 1.12-1.76) and 1.32-fold (95%CI 1.05-1.66), respectively. Hypothyroidism was associated with increased risk of ADHD for Hispanic (HR 1.38, 95%CI 1.14-1.69), African-American, and Other/Multiple racial/ethnic groups. However, the association for the last two racial groups failed to reach statistical significance. Although boys are four-times as likely as girls to be diagnosed with ADHD, hypothyroidism affect both sex equally. Our results suggest that hypothyroidism is associated with increased risk of childhood ADHD in some ethnic and racial minorities. Maternal hypothyroidism may help identify at-risk children who could benefit from greater surveillance and interventions. Additional studies are also needed to determine if treatment of maternal hypothyroidism may lower the risk of this common neurodevelopmental disorder.