Parents who smoke on balconies, outside their homes, or near open windows may still be exposing their children to harmful tobacco residues that disrupt sleep, according to a new study published in Scientific Reports.
Researchers from Clalit-Soroka Medical Center and Ben-Gurion University of the Negev found that children exposed to cigarette smoke had poorer sleep quality, shorter sleep duration, and significantly more nighttime awakenings. Measurable nicotine exposure was also detected in children whose parents reported smoking only outside the home.
The findings highlight growing concern over third-hand smoke, toxic tobacco residues that remain on clothes, hair, skin, and household surfaces long after a cigarette has been extinguished. Unlike many previous studies that relied primarily on parental reports, the Clalit-Soroka and BGU team combined overnight laboratory sleep studies with urine cotinine testing, an objective biological marker of nicotine exposure.
The study included children aged 1–12 who underwent sleep evaluations for snoring, obstructive sleep apnea, or other sleep-related breathing disorders. Nearly half lived in households where at least one parent smoked.
Children underwent comprehensive overnight sleep studies using polysomnography to measure brain waves, airflow, chest movements, blood oxygen levels, heart rate, and muscle activity, allowing researchers to assess both respiratory issues and non-respiratory disruptions to sleep architecture. Urinary cotinine, considered the gold standard for detecting nicotine intake or second-hand contact, provided an objective measure of recent tobacco exposure. Levels correlated directly with poorer sleep efficiency and increased arousals.
Researchers found a clear relationship between nicotine exposure and sleep quality. Children with higher cotinine levels slept less efficiently, spent less time asleep, and experienced 67% more nighttime arousals than children with lower or no exposure.
One of the study’s most striking findings was the disconnect between parental perception and biological evidence. Although urine tests confirmed nicotine exposure, around 60% of parents reported that their children had not been exposed to cigarette smoke, confirming a broader pattern of underreporting in which many parents remain unaware of, or reluctant to acknowledge, third-hand smoke transfer via surfaces and clothing.
“Many parents believe that smoking outdoors protects their children,” said Professor Ariel Tarasiuk, Director of the Sleep Disorders Unit at Clalit-Soroka. “Our findings suggest that this is not always the case. Tobacco smoke residues can travel indoors on clothing and hair, meaning children may continue to be exposed even when smoking occurs outside.”
Professor Tarasiuk added that smoking in another room, on a balcony, or near an open window cannot fully prevent exposure. “The only effective way to eliminate children’s exposure to tobacco smoke is to maintain completely smoke-free homes and vehicles,” he said.
The researchers emphasise that the consequences extend beyond poor sleep. Fragmented sleep during childhood has been associated with impaired learning, attention difficulties, behavioural problems, and obesity, making tobacco smoke exposure an important and preventable public health issue.
Experts not involved in the study, such as Professor Iris Haimov from the Max Stern Yezreel Valley College, noted that uninterrupted sleep in early years is foundational for brain development, cognitive function, and overall health, and that short and fragmented sleep carries risks including cognitive impairment and diminished family quality of life.
The team recommends that healthcare providers routinely ask about household smoking when evaluating children with sleep disorders. They encourage parents to recognise that tobacco smoke exposure does not necessarily end when the cigarette is extinguished.
This Israeli research adds to the body of evidence on environmental tobacco smoke and child health, underscoring the need for smoke-free environments to support better sleep and development in young children.