Homeostatic Regulation of Sleep in Short Sleepers

Sleep is a fundamental biological process essential for maintaining brain and systemic homeostasis, playing a key role in regulating cognitive, metabolic, and emotional functions. Over the past decades, numerous studies have shown that chronic sleep deprivation is associated with an increased risk of cardiovascular disease, diabetes, metabolic disorders, and cognitive deficits.

However, individuals differ in the amount of sleep they need for optimal functioning, suggesting inter-individual variability in homeostatic sleep regulation. Slow waves during sleep (0.5-4 Hz) are central to this regulation and closely reflect sleep pressure accumulated during wakefulness. During deep sleep, slow waves support the reorganization of neural connections, brain detoxification, and restoration of energy reserves. A reduction in slow-wave power, observed with aging or in pathological conditions, has been linked to reduced recovery capacity and increased cognitive vulnerability.

Sleep need is partly determined by genetics and varies between individuals. Approximately 5-7% of the population are short sleepers, able to maintain optimal cognitive and emotional performance despite sleeping ≤6 hours per night. Previous research suggests that short sleepers may compensate for shorter sleep by increasing sleep depth in the early phases, allowing faster recovery than hypersomnia patients.

At the other end of the spectrum is idiopathic hypersomnia (IH), a condition marked by excessive sleep need and persistent daytime sleepiness despite prolonged nocturnal sleep. Its pathophysiology remains poorly understood but may involve altered slow-wave regulation and impaired homeostatic sleep pressure.

The goal of this study is to compare slow-wave architecture among short sleepers, normal sleepers, and individuals with idiopathic hypersomnia to better understand inter-individual differences in sleep homeostasis. We hypothesize that delta power decay during the first night of recording will be faster and more pronounced in short sleepers, reflecting accelerated dissipation of sleep pressure, while it will be slower and less marked in IH patients, indicating impaired homeostatic regulation. This project will provide a detailed assessment of the neurophysiological mechanisms underlying differences in sleep profiles and their implications for health and cognitive functioning.