Higher nighttime temps linked to increased risk of autism diagnosis in children – study

Nighttime temperatures during pregnancy may be linked to a higher chance of an autism diagnosis in children, a recent study suggests.

The research tracked nearly 295,000 mother-child pairs in Southern California from 2001 to 2014 and linked warmer overnight temperatures with higher risk in early and late pregnancy.

Children of mothers exposed to higher than typical nighttime temperatures during weeks one to 10 of pregnancy had a 15 per cent higher risk of an autism diagnosis.

Exposure during weeks 30 to 37 was linked to a 13 per cent higher risk.

 Lead author David Luglio, a post-doctoral fellow at Tulane University, said: “A key takeaway is that we identified specific windows when a mother and her developing child can be most affected by exposures to higher nighttime temperatures.

“This is critical and hopefully can help mothers prepare accordingly.”

The study is described as the first to examine how temperature may affect fetal neurodevelopment, the process by which a baby’s brain and nervous system form during pregnancy.

Extreme temperatures linked to increased risk were classified as above the 90th percentile, meaning 3.6°F hotter than average, and the 99th percentile, 5.6°F above average.

The association held even after researchers accounted for factors such as neighbourhood conditions, vegetation and fine-particle air pollution.

The study could not account for other factors such as access to air conditioning. Researchers did not find the same association with daytime temperatures, potentially because people spend more time away from home during the day.

“Heat waves are becoming more frequent, and people may only think of the dangers of daytime heat exposure,” said Mostafijur Rahman, assistant professor of environmental health sciences at Tulane University.

“These results indicate a strong association between high nighttime temperatures during pregnancy and autism risk in children and show that we need to think about exposure to heat around the clock.”

The study did not examine how higher temperatures at night might affect prenatal development, though Luglio said it is possible that warmer nights disrupt sleep for pregnant mothers.

Previous research has suggested insufficient sleep during pregnancy may be linked to a higher risk of neurocognitive delays in children.

“Extreme heat exposure during pregnancy has been linked to a range of adverse health outcomes, including prenatal neurodevelopment delays and complications with an embryo’s development of a central nervous system,” Luglio said.

“The goal of our study was to specifically explore the link between prenatal heat exposure and autism diagnoses for the first time.”