I’m sorry we broke up this morning,
I want you back!”
IMAGINE YOUR INTERNAL CLOCK RUNS ON VANCOUVER TIME…
BUT YOU LIVE IN TORONTO
- Our brain regulates many functions (sleep-wake cycle, core body temperature, cortisol secretion, etc.) over a 24-hour period.
- This is called the intrinsic circadian rhythm (aka your body clock).
- It is sensitive to light (both natural and artificial), and daily routine (e.g., time of meals, period of activity or inactivity, etc.).
Generally, we are “wired” to be awake when it is light outside and asleep when it is dark outside.
- Our circadian rhythm (i.e., internal clock) is in fact longer than 24 hours (it’s actually about 25 hours), hence the importance of keeping a regular schedule to “wind up” our body clock and manage the natural drift.
Circadian rhythm sleep-wake disorders (CRSWDs) happen when there is a desynchrony or mismatch between the intrinsic circadian rhythm and the external environment (24-hour solar day).
Relative to social norms (i.e., people without this problem) and environmental clock, sleep can either be:
- markedly delayed (“night owls”),
- markedly advanced (“morning birds”), or
- irregular (sleep episodes of less than 4 hours at a time; however, the total sleep duration over a 24-hour period can be normal).
- Up to 1.7% of the general population and between 5-10% of chronic insomniacs in sleep clinics suffer from delayed sleep-wake phase disorder (DSWPD).
- DSWPD prevalence is the highest in adolescence; up to 7% of teenagers are affected.
- Women and men seem to be equally affected.
- About 1% of the general population is affected by advanced sleep-wake phase disorder.
- Irregular sleep-wake disorder has been described in neuro-development disorders, neuro-degenerative disorders and after moderate to severe TBI.
Preliminary results show that delayed sleep-wake phase disorder (DSWPD) is probably the most common CRSWD after concussion.
Causes of CRSWDs are not well understood.
Some proposed hypotheses include:
- Developmental changes in sleep-wake timing,
- Lengthening of the intrinsic circadian rhythm during adolescence,
- Changes in light exposure or sensitivity,
- Altered sensitivity of circadian system to light,
- Social, genetic, and behavioural factors, and
- Disruption (after TBI) of systems regulating the circadian rhythm (alteration of neural plasticity, suprachiasmatic nucleus function, gene expression and/or melatonin secretion).
CRSWD is a diagnosis made clinically based on the sleep history and sleep diary.
- The disorder often begins in adolescence or after concussion.
- Concomitant depression or insomnia is common.
- Those experiencing insomnia on top of DSWPD notice that even on weekends or vacations they experience difficulty falling asleep or staying asleep overnight.
- Actigraphy watches may be used in patients unable to keep a sleep diary (e.g., those with neurodegenerative diseases or severe TBI).
- Salivary melatonin immunoassays are used in research setting but not routinely used in clinical practice yet; further studies are required.
- Polysomnography (sleep study) is not useful unless another underlying sleep disorder (e.g., obstructive sleep apnea) is suspected.
Patients with delayed sleep-wake phase disorder (DSWPD) often reports symptoms of:
- Sleep onset insomnia: Difficulty falling asleep if sleep is attempted at a socially desired or required bedtime (usually before midnight or before 11PM for those 14 years old or younger).
- Waking up too early: Conventional rise times imposed by professional, academic or familial/personal obligations make it quite difficult to wake up and feel alert. When unrestricted, on weekends or vacations for example, these patients go to bed late (without difficulty falling asleep) and sleep well into the morning, noon or even later, and report good sleep quality and duration.
- Insufficient sleep and/or excessive daytime sleepiness: Attempts to follow a socially required sleep schedule results in a sleep deficit. Most adults need about 7 to 9 hours of sleep per night while teenagers require about 8-10 hours.
- Performance and Social Consequences:
- Low energy, generalized malaise during the day
- Poor school or work performance, difficulty focusing or thinking
- Depressed mood, poor response to antidepressant, decreased quality of life, irritability, anxiety
- Chronic tardiness, repeated school/work absences, family discord
- Most patients respond well to behavioural modifications and education about healthy sleep.
- The primary goals are to gradually advance the bedtime and rise time to a schedule that aligns with social and occupational constraints, as well as to avoid poor sleep habits that may exacerbate or contribute to the problem.
- In refractory patients, timed oral melatonin before bedtime or post-awakening light therapy can be added.
- The use of sleeping pills is discouraged.
Consensus Conference Panel, Watson NF, Badr MS, et al. Recommended amount of sleep for a healthy adult: A Joint Consensus Statement of the American Academy of Sleep Medicine and Sleep Research Scoeity. J Clin Sleep Med 2015; 11:591.
Gradisar M, Cohnt H, Gardner G et al. A randomized controlled trial of cognitive-behavior therapy plus bright light therapy for adolescent delayed sleep phase disorder. Sleep. 2011 Dec 3;34(12):1671-80.
International classification of sleep disorders: diagnostic and coding manual. 3rd ed. Westchester (IL): American Academy of Sleep Medicine; 2014.
Sharkey KM, Carskadon MA, Figueiro MG, et al. Effects of an advanced sleep schedule and morning short wavelength light exposure on circadian phase in young adults with late sleep schedules. Sleep Med. 2011 Aug; 12(7):685-92.
Zalai DM, Girard TA, Cusimano MD, et al. Circadian rhythm in the assessment of postconcussion insomnia: a cross-sectional observational study. CMAJ 2020; 8(1):E142-147.