Def: chronic (>3 months) major delay (>2-3 hrs) in sleep-wake timing vs desired or required schedule
Prevalence 1-10%
More common in teens and young adults, can start in childhood
Family hx common (up to 40%)
Consequences of social schedule:
1. Sleep onset insomnia
2. Difficulty waking at acceptable time, may cause sleep inertia (sleep drunkenness)
3. Chronic sleep restriction
4. EDS, esp in the morning
5. Impaired performance across domains
Clinical features
On self-selected schedule, sleep quality and duration improve but stay delayed
Delayed wake maintenance zone (2-3 hrs of peak alertness before evening melatonin rise)
Pts often feel alert and productive late at night
Increased risk of substance dependence: hypnotics (alcohol, cannabis, Rx) or stimulants (caffeine, amphetamines)
Associated conditions
- Mood d/o: MDD, bipolar
- Anxiety d/o, esp OCD
- Neurodevelopmental d/o, esp ADHD and ASD
Pathophysiology
Excess evening light: devices, indoor lighting
Behavioral delays from habit, OCD (pre-bed checking), ADHD (trouble going to bed)
Inadequate morning light: rebound sleep, clinophilia (excess time in bed), little outdoor light (e.g. mood d/o)
Possibly weaker sleep homeostatic drive
Assessment
Careful sleep hx, attention to known or suspected psych comorbidities
Chronotype questionnaires useful but do not replace hx
ICSD-3: sleep diary and/or actigraphy ≥7 days, ideally 14 days, including work/school and free days
DLMO and core body temp minimum may separate true circadian from behavioral DSWPD, but limited availability
Repeat diary and actigraphy to assess tx response
Ad lib PSG (at preferred timing) occasionally helpful to find comorbid OSA or PLMD
Treatment
Tailored to the individual
Chronic d/o with frequent relapses, set expectations and commitment to compliance
1. Behavioral measures
Sleep timing education: body clock, light, sleep pressure
Limit evening light: low indoor lighting, ideally at floor level
Sunglasses outdoors on summer evenings
Blue-light blocking (amber) glasses
Morning light: scheduled outdoor light ≥20 min after waking
Scheduled exercise at the same time daily, ideally before late evening
Scheduled meals at the same time daily
CBT-I elements: stimulus control, anchor times, sleep scheduling
2. Melatonin
Use as a chronobiotic, not a hypnotic
Low doses are more effective
3. Light therapy
20 min, ideally natural light, or light box
As close as possible to waking, or 60-90 min before habitual wake time if tolerated
Commercial light boxes deliver 10,000 lux at 30-85 cm
Serial advances: Once a stable new schedule is reached, recalculate free-day midpoint of sleep and move tx timings earlier
Typically up to 3 serial advances
- Oxford Handbook of Sleep Medicine 2022