Non-24-Hour Sleep-Wake Syndrome

Ina Keyser10144383

FLG 327

University of Pretoria17 October 2012

Figure 1: Woman Sleeping

Non-24-Hour Sleep-Wake Syndrome

Also known as: free-running type circadian arrhythmia

DEF: Chronic sleeping disorder

Normal Physiology

Circadian Rhythms Latin origin: circa means “around” and diem

means “day”

Biological process that displays an endogenous, entrained oscillation of 24 hours

Self-sustained and adjust to the local environment by external cues (zeitgebers)

Important zeitgeber = daylight

Normal Physiology CONTINUED

Suprachiasmic nucleus (SCN) is a group of cells located in the hypothalamus

Receives information through illimination of the eyes

Retina contain photosensitive ganglion cells which contains melanopsin

Signals follow a pathway, known as the retinohypothalamic tract to SCN Figure 2: Sagittal Section of Brain

Normal Physiology CONTINUED

SCN takes the information, interprets it and passes it on to the pineal gland (epithalamus)

Pineal gland secretes melatonin

Melatonin peaks at night and ebbs during the day

Figure 2: Sagittal Section of Brain

Normal Physiology CONTINUED

“Internal biological clock” or circadian rhythm adheres to a 24 hour cycle

Daily variances are caused by environmental factors: physical or emotional stress

These variances even out and stabilises again to a 24 hour cycle

No harmful effects to the body

Non-24-Hour Sleep-Wake Syndrome No internal clocks that resets balances within a 24

hour schedule Body insists that the day is longer than 24 hours

Circadian rhythm function over longer periods of time

e.g. 72 hour cycles: stay awake for 48 straight hours and then sleep for 24 straight hours as a regular sleeping pattern

Most cases fall within a 25 to 27 hour range.

Non-24-Hour Sleep-Wake Syndrome CONTINUED

N24 makes it impossible for the individual to sleep at normal (socially accepted) times

Untreated N24 causes a person's sleep-wake cycle to change every day

Degree related to how much over 24 hours the cycle lasts

The cycle progresses around the clock, eventually returning to "normal" for one or two days before "going off" again

Figure 3: Woman Awake

Prevalence Most cases reported in medical literature occurred in blind individuals

50% of completely blind individuals present with N24

Circadian arrhythmia can occur at any age, from birth onwards

Generally follows shortly after loss or removal of the individual’s eyes or damage to the retina

The first detailed study of N24 was made on a blind subject

28-year-old male presented with a 24.9-hour sleep cycle (as well as plasma cortisol and other parameters).

Even while adhering to a 24-hour schedule for bedtime, rise time, work and meals; the man’s body rhythms continued to shift.

  Rare among visually impaired individuals (maintain some light perception)

Research suggest, low light exposure can synchronize the body clock 

Prevalence CONTINUED

N24 have been reported in sighted individuals

BUT very rare and the etiology is less well understood in these cases

Since 2005, less than 140 cases reported

• cranial injury• pituitary adenoma removed (involving the optic chiasma)

N24 is thought to involve abnormal functioning of the SCN abnormal secretions of melatonin

Thus neurological in origin

Figure 4: Pituitary Adenoma

Signs and SymptomsDifficulty in adjusting to changes in "regular" sleep-wake cycles, due to:

• stress• evening activities• travel to different time zones• vacations• illness and use of medications (especially stimulants or sedatives)• changes in daylight hours in different seasons• time changes e.g. daylight savings time• growth spurts (which cause fatigue)

Commonly impairs their ability to function socially and occupationally

Characteristically, they are "partially or totally unable to function in scheduled activities on a daily basis, and most are unable to work at conventional jobs" [1]

Attempts to keep to the social and conventional hours, patients may develop insomnia (not a normal symptom of N24) and excessive sleepiness during the day

Figure 5: Girl in Class

Signs and Symptoms CONTINUED

Side-effects associated with acute and chronic sleep deprivation:

• Cognitive dysfunction• Confusion• Diarrhoea• Extreme nausea• Extreme fatigue• Hair loss• Headaches Figure 6: Man Sleeping at

Work

Diagnosis and PrognosisDiagnosis: History of your past sleeping routines Medical history Recent changes in your lifestyle Drug or medication use Neurological test e.g. ECG Body temperature and melatonin levels

Prognosis: Attempt to reset and balance your circadian rhythm

Fixed schedule at set times no matter when you wake up

Melatonin hormone therapy is the most widely used treatment Chronotherapy and acupuncture

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8. "Gene Discovered in Mice that Regulates Biological Clock". Chicago Tribune. 29 April 1994.