Circadian Rhythm Sleep-Wake Disorders
Circadian rhythm sleep-wake disorders occur when the internal body clock does not align with the schedule required by school, work or the environment.
Sleep may be good at the person’s own biological time
A person may sleep well when allowed their preferred timing yet experience insomnia or severe sleepiness when required to sleep or wake at a different hour. This is not simply a bad habit, and a preference for late nights is not a disorder without persistent symptoms and functional impact.
Recognised patterns include delayed or advanced sleep phase, irregular sleep-wake rhythm, non-24-hour rhythm and shift-work disorder. Light is the strongest environmental timing signal, so when light, darkness and treatment are used can matter as much as the intervention itself.
Assessment
- A persistent or recurrent sleep disturbance is driven mainly by an altered circadian system or mismatch between internal rhythm and the required schedule.
- The pattern produces insomnia, excessive sleepiness or both and causes clinically significant distress or difficulty functioning.
- A sleep diary and often actigraphy across work and free days reveal whether the timing is stable, delayed, advanced, fragmented or progressively moving.
- Insufficient sleep, insomnia, sleep apnoea, narcolepsy, medicines, substances, mood episodes and the real demands of shift work are considered.
Timed treatment
Treatment may use a consistent schedule, gradual timing shifts, carefully timed bright light and planned reduction of light at other hours. Abrupt large changes are usually harder to sustain than a staged plan.
Melatonin may help selected patterns, but taking it at the wrong time can shift the clock in the opposite direction and should be clinically guided. Shift-work plans may combine scheduling, planned sleep, light and workplace safety; medication cannot substitute for adequate rest.
When to seek help
Seek assessment when timing difficulties continue for weeks or months, cause repeated absence or inability to wake, or create dangerous driving sleepiness. Bring a diary and actual work schedule. Sudden major sleep change with manic or depressive symptoms needs mental-health and medical review.