The Causes of Autism

JAMA Pediatrics. 2019;173(1):86-92

Who are the beautiful authors?

Lief Pagalan, MSc; Celeste Bickford, BSc; WhitneyWeikum, PhD; Bruce Lanphear, MD; Michael Brauer, ScD;Nancy Lanphear, MD; Gillian E. Hanley, PhD; TimF. Oberlander,MD, FRCPC; Meghan Winters, PhD

What is this study about?

A study was conducted in Metro Vancouver, Canada, to evaluate the association between prenatal exposure to airborne pollutants and autism spectrum disorder (ASD) in a large population-based cohort. The study found an association between exposure to nitric oxide (NO) and ASD, but no significant association with particulate matter (PM) or nitrogen dioxide. The study is one of the largest population-based cohorts on ASD and air pollution.

What previous research is there on this topic?

Previous studies from the USA, Israel, and Taiwan have found positive associations between particulate matter, nitric oxide, and nitrogen dioxide exposures with increased risk for autism. However, three studies in Europe observed no associations.

What were the methods used in this study?

The study utilized high-resolution exposure estimates and strict diagnostic criteria for all children positively identified with ASD in one of the largest population-based birth cohorts. The study used data from the British Columbia Perinatal Data Registry, the British Columbia Medical Service Plan, hospital discharge data, Statistics Canada data, and the British Columbia Autism Assessment Network.

The study calculated temporal factors, minimum concentrations, and Pearson correlation coefficient matrix to evaluate pollutant independence. The study examined the association between air pollution exposure and the odds of ASD using logistic regression and odds ratios.

How was the data collected?

The study analyzed the association between air pollutant concentrations and the likelihood of developing ASD in children born in Vancouver between 2003 and 2009. The study used land use regression (LUR) models to develop exposure estimates for the first birth in 2004 and followed the cohort until the end of 2014 to establish a minimum 5-year follow-up period for ASD diagnoses.

What were the findings?

The study found that adjusted odds ratios for ASD per interquartile range (IQR) were not significant for exposure to PM during pregnancy, but the odds ratio was significant for nitric oxide exposure. Odds ratios for male children were significant for all three pollutants, while for female children, odds ratios were significant only for NO. The authors also conducted sensitivity analyses, but exposure to nitric oxide remained significantly associated with an increased risk of ASD even after adjusting for additional covariates.

What were the limitations of the study?

The study was conducted in a population with relatively low levels of air pollution. Therefore, the findings may not be generalizable to populations exposed to higher levels of air pollution.

The study relied on a retrospective design, which may introduce recall bias and limit the ability to draw causation between air pollution exposure and ASD.

The study used a population-based birth cohort of children in British Columbia and did not include children diagnosed by private practitioners. Therefore, the diagnostic criteria may not be entirely representative of all ASD cases in the region.

The study did not account for exposure to other environmental factors that could contribute to the development of ASD.

What should future research look into?

Investigate the link between prenatal exposure to various air pollutants and the risk of developing ASD, including exposure to mixed pollutants.

Conduct a study in a population with high levels of air pollution to confirm previous findings and evaluate their generalizability.

Determine the critical window of sensitivity for ASD by examining the effects of air pollution exposure during specific trimesters of pregnancy.

Assess other environmental factors that may contribute to ASD development and incorporate them into future studies.

Consider using prospective studies to validate findings from previous retrospective research and provide more reliable evidence about the relationship between prenatal exposure to NO and ASD.

Investigate differences in exposure and response to air pollution across different subgroups of individuals, such as race, ethnicity, and income.

By exploring these research avenues, we can gain a better understanding of the complex relationship between air pollution and ASD, ultimately leading to improved prevention and treatment strategies.

Can I read the full study somewhere?

Of course you can gorgeous. Step inside.