Irregular Sleep-Wake Rhythm (Fragmentation)

Irregular sleep-wake rhythm (fragmentation) is a circadian rhythm sleep-wake disorder characterized by the absence of a single, defined period of nighttime sleep and daytime wakefulness. Instead of a consolidated 24-hour cycle, an individual’s sleep is broken into multiple short bouts — resembling naps — scattered throughout the day and night. This fragmentation is often driven by a weakening of the body’s internal master clock or a flattening of melatonin secretion, and it is highly prevalent in neurodegenerative conditions and bipolar disorder (BD). In the context of mood disorders, this lack of rhythm stability is a significant risk factor for episode relapse, as the brain loses the restorative benefits of continuous, deep sleep