Objectives: To study head circumference (HC) growth in children with ASD using longitudinal data from a prospective population-based child cohort in Norway.
Methods: HC measures were obtained prospectively from birth until 12 months of age. Cases of ASD in the cohort were identified through questionnaire-based screening, referrals of suspected ASD cases, and record linkages to Norwegian specialist health services. Head growth trajectories in ASD cases and non-cases were compared through parametric modeling of growth curves.
Results: The study sample included 90,159 children, of whom 249 (0.28%) had been diagnosed with ASD, 203 boys and 46 girls. An average of 4.1 HC measures per child was available. For ASD boys, mean head size was similar to that of other boys at birth, and the trajectory for mean head growth overlapped with the overall mean trajectory for boys at all ages from birth until 12 months. There was an increase in the prevalence of macrocephaly (HC > 97th population percentile) by age, to 11.8% at age one year (95% CI, 6.2-19.6%, p<0.001). Macrocephaly was accompanied by a similar relative increase in mean length; when head size was adjusted for length, the proportion above the 97th population percentile at age one year was 2.0% (95% CI, 0.2-6.9%, p=0.77). Correspondingly, the prevalence of microcephaly (HC < 3rd population percentile) was 2.9% at one year (95% CI, 0.2-8.4%, p=1.00), but after adjustment for length, the proportion below the 3rd population percentile was 6.9% (95% CI, 3.2-6.4%, p=0.03). When mean head size was adjusted for length, ASD boys fell below the population mean from age six months onwards, and the downward deviance was significant by one year of age (p=0.02). In girls with ASD, mean HC was 0.44 cm lower compared to non-cases at birth (p=0.05), and the difference increased gradually to 0.7 cm at one year of age (p=0.001). ASD girls also had an increased prevalence of microcephaly. For all HC measures in this group combined, 7.3% were below the 3rd population percentile (95% CI, 3.8-12.4%, p=0.004), but after adjustment for length, the proportion below the 3rd percentile was reduced to 4.4% (95% CI, 1.8-8.9%, p=0.34), i.e., not significantly different from the population mean of 3%. Like in ASD boys, mean head size adjusted for length fell below the population mean from age six months onwards. Macrocephaly in ASD girls only occurred at one instance, for a girl at age one year.
Conclusions: Head growth patterns in ASD children diverge from those of the general population, and the differences are sex-specific. Previous findings of accelerated mean head growth in ASD were not replicated.
See more of: Psychiatric/Behavioral Comorbidities
See more of: Symptoms, Diagnosis & Phenotype