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As our understanding of sleep evolves, a recurring recommendation remains that adults should sleep in a single, uninterrupted nocturnal bout – commonly referred to as monophasic sleep. However, the scientific foundation for this standard may be less canonical than previously assumed, particularly when considering individual variability in sleep needs and organization. Historical texts and recent research suggest an alternative view: that sleep can be naturally segmented into two periods across the 24h cycle – a pattern known as biphasic sleep. This review explores the physiological implications of biphasic sleep, examining its potential benefits and limitations under healthy conditions and in particular contexts, such as shift working. With this available data, an original hypothesis is proposed, consisting of a novel framework of sleep distribution according to sleeping types. This aims to stimulate new research about biphasic schedules and how sleep architecture might adapt to them over time. The strengths and weaknesses of existing research will be critically assessed, culminating in recommendations for future investigations and methodological approaches. These insights may ultimately inform more personalized and flexible sleep guidelines better aligned with individual and societal needs. • Biphasic sleep may be a natural, culturally common alternative to monophasic sleep. • Biphasic sleep may help offset sleep loss in shift work, new parents, and students. • Mid-night wakefulness might reflect a normal sleep pattern in certain individuals. • A flexible sleep model may better suit individual chronotypes and daily demands.
Sena-Ribeiros et al. (Wed,) studied this question.