Sleep Slow-Wave and Spindle Alterations in Young Smokers Correlated With the Severity of Cigarette Exposure

Smoking is closely associated with significant disruptions in sleep architecture. Although previous studies have reported altered self-reported sleep quality in adolescent smokers, relatively few studies using polysomnography have objectively examined critical sleep microstructural components (i.e., slow-wave activity and sleep spindle characteristics) in young smokers. This study investigated changes in these electroencephalographic indices in adolescent smokers and their associations with smoking-related characteristics. We recruited 20 young smokers and 16 non-smokers, collecting their overnight polysomnography data. The Fagerström Test for Nicotine Dependence assessed dependence levels, and the pack-year index quantified cumulative smoking exposure. We analysed slow waves (0.5–4.5 Hz) in N3 sleep and spindles (11–16 Hz) in N2 sleep, quantifying parameters via the YASA toolbox. Smokers showed impaired N3 slow-wave integrity (reduced amplitude and slopes) and enhanced N2 spindle activity (increased density, frequency and duration). Slow-wave amplitude reduction correlated negatively with smoking indices, whereas spindle enhancements correlated positively. Sleep slow waves and spindles may serve as biomarkers for sleep quality in young smokers, deepening understanding of the sleep–smoking relationship.