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High Levels of Prenatal Smoking Exposure Affect Sleep Patterns in Preterm Neonates

WESTCHESTER, Ill -- December 2, 2008 -- A study in the December 1 issue of the journal Sleep is the first to show that high levels of prenatal smoking exposure strongly modify sleep patterns in preterm neonates, which places infants at a higher risk for developmental difficulties that could persist throughout early and middle childhood.

Results indicate that preterm neonates born to heavy-smoking mothers who smoked more than 10 cigarettes per day displayed disrupted sleep structure and sleep continuity. From 7:00 PM to 8:00 AM they slept almost 2 hours less than controls who were born to nonsmoking mothers, and their sleep was more fragmented. Compared with controls, neonates born to both heavy and low smokers displayed more body movements and, as a result, more disturbed sleep.

Frederic Telliez, University of Picardie Jules Verne, Amiens, France, said that sleep integrity is critical in the brain development of neonates. Disruption of sleep mechanisms by prenatal smoking exposure may predispose neonates to alterations in some physiological function (such as ventilation) and can result in long-term neurocognitive disorders.

For the study, 40 healthy preterm neonates (postconceptional age approximately 33.9 weeks) were recruited from the neonatal intensive care unit at Amiens University Medical Center. Mothers were subjectively asked how many cigarettes they had smoked during their pregnancy in order to determine the level of in utero exposure to smoking.

Neonates born to mothers who did not smoke at all during the pregnancy were placed in the control group; infants born to mothers who smoked less than 10 cigarettes per day were placed in the low-smoking group; and those whose mothers had smoked more than 10 cigarettes per day were placed in the heavy-smoking group.

All children were free of neurological, respiratory, and cardiac disorders and had not received caffeine treatment or oxygen therapy. Neonates whose mothers reported substance abuse or passive smoking were excluded from the study. None of the infants had suffered from sleep deprivation in the 48 hours prior to the sleep recording session.

Infants received overnight polysomnographic recordings in isolated rooms. Researchers measured sleep period time, beginning at the first sleep onset and the ending at the last awakening; the percentage and frequency of wakefulness after sleep onset; and total sleep time. Special attention was paid to the number and duration of body movements.

Findings indicated that even after 29.7 days without postnatal exposure to smoking or nicotine, and despite the fact that neonates in the heavy-smoking group were nearly 10 days older, infants exposed in utero to high levels of smoking still showed an altered organisation of the various behavioural states.

The authors suggested that examining the neurodevelopmental trajectories of neonates exposed to maternal smoking (and of those who were not) could lead to greater understanding of potential deficits in the exposed group, better prediction of outcomes, and potentially more effective compensatory clinical interventions. Researchers also stated that longitudinal studies are necessary to assess the persistence of behavioural state effects caused by prenatal smoking exposure.

SOURCE: American Academy of Sleep Medicine

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