Def: sleep-wake cycle desynchronized from the solar cycle
Period length typically >24 hrs
Sleep onset delays progressively, usually 20-60+ min per day
ICSD-3: sx ≥3 months, diary or actigraphy ≥14 days showing daily delay
Epidemiology
Seen in blind (esp no light perception) and sighted pts
≥50% of totally blind individuals may have Non-24
Associated conditions
- Schizophrenia
- Personality d/o
- Bipolar d/o
- Alzheimer’s dz
- Optic nerve hypoplasia, often with agenesis of corpus callosum
Pathophysiology
Totally blind: no photic entrainment, clock free-runs at intrinsic period slightly >24 hrs
Some retinal d/o spare melanopsin-containing retinal ganglion cells, preserving some entrainment
Assessment
Careful hx: past psych hx, current mental state, sleep behavior
Serial DLMO can show a free-running rhythm, used to estimate intrinsic period
Treatment
Tx is difficult, relapses are common
1. Blind pts
Tasimelteon (Hetlioz) FDA approved for Non-24 (2014), 20 mg 1 hr before bedtime
2. Sighted pts
Properly timed light exposure is key
Clearly set light-dark cycles:
a. Scheduled activity
b. Morning outdoor light
c. Avoid evening light
d. Darkness at night
Identify and treat comorbid psych issues
Short-term timed hypnotics or stimulants as adjunct, monitor for dependence
- Oxford Handbook of Sleep Medicine 2022