Circadian rhythm sleep disorders

Core characteristics

Symptoms typically include difficulty falling asleep or staying awake at socially expected times, fragmented sleep, and daytime sleepiness or insomnia. These problems often coexist with disturbances in other daily rhythms such as appetite, core body temperature and hormone cycles. Cognitive performance, mood and metabolic regulation can be affected when sleep timing is chronically misaligned.

Common types

• Delayed sleep-wake phase disorder: habitual late sleep onset and late wake times.
• Advanced sleep-wake phase disorder: early evening sleepiness and early-morning awakening.
• Non-24-hour sleep-wake rhythm: a sleep pattern that progressively shifts later each day, common in people who are blind.
• Irregular sleep-wake rhythm: fragmented sleep, with multiple naps and no clear main sleep period.
• Shift work disorder and jet lag: externally imposed schedule changes that conflict with the internal clock.

Causes, diagnosis and assessment

Causes include genetic predisposition, altered light exposure, work schedules, travel and reduced light perception. Assessment relies on clinical history, sleep diaries, actigraphy and sometimes melatonin or core body temperature measurements. The diagnosis distinguishes these disorders from insomnia and other sleep conditions that primarily affect sleep quality rather than timing; see also links about sleep and daily rhythms like appetite.

Treatment and management

Management aims to realign sleep timing using light therapy, appropriately timed melatonin, gradual schedule changes (chronotherapy), strict sleep hygiene and behavioral strategies. For shift workers, optimizing shift schedules, controlled light exposure and planned naps can reduce impairment. Treatment plans are individualized and may combine several approaches.

Importance and prognosis

When recognized and treated, many people can improve sleep timing and daytime functioning, though some forms are chronic. Early identification and workplace or social accommodations often reduce the personal and societal impact of these disorders.