Head circumference values among Inuit children in Nunavut, Canada: a retrospective cohort study.

Background: Inuit children from Nunavut have been observed to have high rates of macrocephaly, which sometimes leads to burdensome travel for medical evaluation, often with no pathology identified upon assessment. Given reports that World Health Organization (WHO) growth charts may not reflect all populations, we sought to compare head circumference measurements in a cohort of Inuit children with the WHO charts.

Methods: We extracted head circumference data from a previous retrospective cohort study where, with Inuit partnership, we reviewed medical records of Inuit children (from birth to age 5 yr) born between Jan. 1, 2010, and Dec. 31, 2013, and residing in Nunavut. To create a cohort of Inuit children similar to the cohorts used in the development of the WHO growth charts, we excluded children with preterm birth, documented neurologic or genetic disease, and most congenital anomalies. We compared head circumference values with the 2007 WHO charts using centiles estimated with a generalized additive model.

Results: We analyzed records of 1960 Inuit children (8866 data points), of whom 993 (50.8%) were female. Most data were from ages 0 to 36 months. At all age points, we found that the study cohort had statistically significantly larger head circumferences than WHO medians, with most z scores for head circumference measurements among Inuit children falling 0.5-1 standard deviations above the WHO reference (p < 0.001). At age 12 months, median head circumferences were 1.3 cm and 1.5 cm larger for male and female Inuit children, respectively. Using WHO growth curves, macrocephaly was significantly overdiagnosed and microcephaly was underdiagnosed (p < 0.001).

Interpretation: Our results support the observation that Inuit children from Nunavut have larger head circumferences than other populations, and use of the WHO charts may thus lead to overdiagnosis of macrocephaly and underdiagnosis of microcephaly. Population-specific growth curves for Inuit children should be considered to provide timely and appropriate diagnoses of microcephaly and avoid overinvestigation of macrocephaly.