Secondhand smoke can disrupt children’s sleep in surprising ways, Israeli researchers say

A groundbreaking study by Israeli scientists has revealed that exposure to secondhand smoke directly harms children’s sleep by acting on the central nervous system, independent of respiratory problems caused by environmental smoke.

The peer-reviewed research showed that children exposed to secondhand smoke slept significantly worse than their peers, even when their breathing was clear and blood oxygen levels remained completely normal.

“Eliminating tobacco smoke from a child’s environment can immediately improve sleep efficiency, brain recovery, and overall pediatric health,” said the study’s co-leader, Prof. Ariel Tarasiuk, via video call.

The researchers called on pediatricians to include questions about parents’ or caretakers’ smoking when children are seen at a clinic or admitted to a hospital.

“Pediatricians probably don’t ask that question, but they should,” Tarasiuk said.

Get The Times of Israel's Daily Edition

by email and never miss our top stories

By signing up, you agree to the terms

The study appeared on Monday in Scientific Reports.

Medical literature shows that environmental tobacco smoke causes inflammation and snoring in young children, Tarasiuk said.

However, he explained that after children were treated for their respiratory problems, “their parents came and said, ‘Look, our child is not snoring as much, but he still moves a lot in bed,’ and so on. This got us interested.”

The first challenge for the researchers was recognizing that parents and caretakers underreported their cigarette smoking.

“Parents do not always accurately confess that they are smoking,” Tarasiuk said. “But we don’t look at it from a judgment point of view. It is partially cultural, partially shame.”

Testing confirmed that nearly half of the children had at least one smoking parent, 60 percent of whom explicitly denied exposing their child to secondhand smoke.

The researchers used questionnaires and measured the cotinine found in the children’s first morning urine. Cotinine is a byproduct created when the body breaks down nicotine.

Nicotine exits the body quickly, so testing for cotinine is the most reliable way to measure recent tobacco use or exposure to secondhand smoke.

“Cotinine is the gold standard to determine tobacco exposure,” Tarasiuk said.  “Think about the morning urine like a window to what happened in prior days.”

The BGU research team evaluated 30 typically developing children, ages 1 through 12, who had been referred to the BGU sleep lab for overnight monitoring due to suspected sleep-disordered breathing.

In addition to measuring cotinine levels, the scientists used polysomnography, a series of tests that measured the children’s brain waves to determine when they were in deep sleep, light sleep, or when their brains were jolted awake or aroused.

The researchers also monitored airflow through the child’s nose and throat, chest movements, blood oxygen levels, heart rate, and muscle activity to assess physical restlessness.

The data revealed a 67% higher arousal index — meaning they experienced more brief shifts in brain activity, bringing them to a lighter sleep or awakened state — than other children not exposed to cigarette smoke. This resulted in highly fragmented, restless sleep.

As cotinine markers rose, the children’s ability to maintain stable, continuous sleep decreased.

The study also revealed a distinct reduction in total sleep time during the night.

Tarasiuk said this proves that tobacco smoke disrupts the central nervous system and alters natural circadian sleep cycles, separately from its physical impact on the children’s lungs and throat.

“Uninterrupted, sufficient sleep during the first 12 years of life is foundational for healthy brain development, cognitive function, emotional regulation, immune strength, physical growth, and metabolic health,” Prof. Iris Haimov of the Max Stern Yezreel Valley College told The Times of Israel.

Haimov was not involved in the study.

“Short and fragmented sleep during childhood carries lasting consequences,” Haimov said, “including cognitive impairment, ADHD-like symptoms, depression, obesity, and a significantly diminished quality of life for the entire family.”

She said she hopes the findings will heighten public awareness about the “critical necessity of healthy pediatric sleep, and the insidious dangers of environmental tobacco smoke.”

“The evidence should serve as an urgent reminder for parents to eliminate smoking within the home, on balconies, and inside vehicles,” Haimov said.

Tarasiuk said that “tobacco smoke sticks to our clothes, to fabric, to our skin. It sticks to furniture.”

He believes that recognizing the impact of environmental tobacco smoke exposure on sleep fragmentation, even in the absence of any breathing problems, “can facilitate targeted guidance and counseling for families.”

“Within a month of stopping smoking, we guesstimate that the amount of pollution will be much less,” Tarasiuk said. “We hope we will get the message across to the public about the importance of minimizing smoking.”