Dietary inflammatory index of mothers during pregnancy and Attention Deficit-Hyperactivity Disorder symptoms in the child at preschool age: a prospective investigation in the INMA and RHEA cohorts

Inflammation provides a substrate for mechanisms that underlie the association of maternal diet during pregnancy with Attention Deficit-Hyperactivity Disorder (ADHD) symptoms in childhood. However, no previous study has quantified the proinflammatory potential of maternal diet as a risk factor for ADHD. Thus, we evaluated the association of maternal dietary inflammatory index (DII^®) scores during pregnancy with ADHD symptoms in 4-year-old children born in two Mediterranean regions. We analyzed data from two population-based birth cohort studies—INMA (Environment and Childhood) four subcohorts in Spain (N = 2097), and RHEA study in Crete (Greece) (N = 444). The DII score of maternal diet was calculated based on validated food frequency questionnaires completed during pregnancy (12th and/or 32nd week of gestation). ADHD symptoms were assessed by ADHD-DSM-IV in INMA cohort and by ADHDT test in RHEA cohort, with questionnaires filled-out by teachers and parents, respectively. The associations between maternal DII and ADHD symptoms were analysed using multivariable-adjusted zero-inflated negative binomial regression models in each cohort study separately. Meta-analysis was conducted to combine data across the cohorts for fitting within one model. The DII was significantly higher in RHEA (RHEA = 2.09 [1.94, 2.24]) in comparison to INMA subcohorts (Asturias = − 1.52 [− 1.67, − 1.38]; Gipuzkoa = − 1.48 [− 1.64, − 1.33]; Sabadell = − 0.95 [− 1.07, − 0.83]; Valencia = − 0.76 [− 0.90, − 0.62]). Statistically significant reduced risk of inattention symptomatology (OR = 0.86; CI 95% = 0.77–0.96), hyperactivity symptomatology (OR = 0.82; CI 95% = 0.72–0.92) and total ADHD symptomatology (OR = 0.82; CI 95% = − 0.72 to 0.93) were observed with increased maternal DII in boys. No statistically significant associations were observed in girls between maternal DII and inattention, hyperactivity and total ADHD symptomatology. We found reduced risk of ADHD symptomatology with increased DII only in boys. This relationship requires further exploration in other settings.