Neonatal Polyunsaturated Fatty Acid Levels in Association with Autism Spectrum Disorders: Results from a California Population-Based Case-Control Study

Background: Polyunsaturated fatty acids (PUFAs) play key roles in neurodevelopment. Only a few studies have examined prenatal PUFAs in association with autism spectrum disorder (ASD), and results have not been consistent. No prior study has examined the association between measured neonatal levels of PUFAs and ASD, yet PUFAs measured in the newborn period may better capture the more biologically-relevant window of PUFA uptake in the developing brain during late pregnancy than measurements earlier in pregnancy.

Objectives: To determine whether levels of PUFAs, measured in neonatal bloodspots, differ in in children with ASD as compared to those without ASD.

Methods: We conducted a population-based case-control study of 500 cases and 500 general population (GP) controls in order to examine maternal and newborn PUFA levels in association with ASD. Cases, identified from the California Department of Developmental Services (DDS), were matched on sex and month and year of birth (2011-2013) to GP controls, who were randomly selected within strata of matching factors from birth certificate files after excluding DDS clients. For neonatal analyses, 200 cases and 200 controls from the larger study were randomly selected. Newborn bloodspots were obtained from the California Biobank Program, and PUFA levels were measured using liquid chromatography-mass spectrometry/high resolution mass spectrometry (LC-MS/HRMS).To adjust for hematocrit, potassium levels were used to normalize PUFA levels.Logistic regression analyses, accounting for matching factors and other potential confounders, were used to calculate odds ratios (ORs) between PUFA levels (as individual fatty acids and as summed classes of n-3 and n-6 PUFAs) and ASD.

Results: PUFAs were quantifiable above background levels in newborn bloodspots and demonstrated sufficient stability and precision in this matrix. With the exception of docosahexaenoic acid (r=0.42, p<.0001), neonatal PUFA levels were not correlated with maternal PUFA levels in mid-pregnancy serum. Geometric mean levels of individual neonatal PUFAs did not significantly differ between cases and controls. In adjusted analyses we did not observe significant associations between quartiles of PUFA levels and ASD, though a non-significant reduction in risk with the highest quartile of n-3 PUFAs was suggested (OR for Q4 v Q1=0.72, 95%CI 0.40, 1.29). When examining extremes of the distribution, we observed a significant reduction in odds of ASD according to the highest 5^thpercentile of n-3 PUFAs (relative to the interquartile range (IQR), OR=0.18, 95%CI 0.04, 0.88). A similar association was found for the highest levels of total PUFAs overall (OR=0.25, 95% CI 0.06, 1.01), along with a suggested increase in risk of ASD for those with the very lowest levels of total PUFAs (lowest 5^thpercentile relative to IQR, OR=2.20, 95% CI 0.92, 5.25).

Conclusions: Findings from this population-based case control study suggest that individuals with the highest levels of neonatal n-3 and total PUFAs may have reduced odds of ASD; however, these associations were estimated with low precision and require replication in other studies. Given the role of PUFAs in fetal brain development, and the fact that neonatal PUFAs represent a critical window for PUFA exposure and neurodevelopment, further examination of these associations is needed.