The importance of sleep
Sleep plays a critical role in functioning. A good nights sleep prepares us for the activities during daytime. But sleep is not a passive state of rest. Sleep is also a time when part of the body is more active. When blood pressure drops and breathing becomes more regular and slower, the release of growth hormones increases. Activities such as muscle growth, cell repair, protein synthesis and digestion are often at peak during sleep.
Factors influencing sleep
People in industrialized countries spend less time outside than before and are often exposed to as little as 1 hour of daylight. Without light, synchronization of the sleep rhythm becomes compromised.
Factors which cause sleep disruption
• Too little daylight to synchronize with the solar day.
• Light outside the solar day.
• Our social rhythm is out of sync with the solar day.
• Our social rhythm varies (shift work, late night out etc).
There is growing evidence that we sleep too little. Short term effects of sleep deprivation include direct physiological effects on hunger hormones. When sleep deprived at night, the hormone ghreline that stimulates appetite, increases in our blood. Food ingestion at night is a time when the body process glucose more slowly and cells have a lower insulin sensitivity than during daytime. Furthermore, sleep restriction accentuates increased activity in regions in the brain involved in reward in response to food stimuli.
Short term effects of sleep deprivation
Already after 3 days of sleep extension in men who habitually sleep for short time periods, positive effects on insulin metabolism and an increase in testosterone was seen.
Long term consequences of sleep deprivation
The long term consequences of sleep deprivation cause widespread health problems. Shift workers, making up 15-20 % of European and US work force are at particular risk of circadian rhythm and sleep disruption. Shift workers have an increased prevalence of cardiovascular disease and cancer and sleeping problems are common.
15% increased mortality risk amongst people who sleep 5 hours or less per night
20% of all motor vehicle accidents in the US are caused by sleep deprivation
30% of the population experience sleep related problems.
33% of drivers have fallen asleep at the wheel
50% of all night shift workers report regularly nodding off and falling asleep when they are at work.
7 hours - amount of sleep most people need per night
6.5 hours - average sleep time
How to improve sleep
Prepare your sleep in advance. Try to wind down and avoid too much light an hour before going to sleep. Try to have regular sleeping schedule and avoid exercise three hours before going to bed as exercise stimulates the body to secrete the stress hormone cortisol. Also avoid food several hours before sleep. Light in the evening can interfere with sleep but bright light in the morning suppress melatonin and helps synchronize the sleep-wake cycle. Try to get enough light during daytime and especially during the early hours.
The Division of Sleep Medicine at Harvard Medical School and WGBH Educational Foundation
Medic et al. Short- and long-term health consequences of sleep disruption Nature and Science of Sleep 2017:9 151–161
Figueiro and White Health consequences of shift work and implications for structural design Journal of Perinatology (2013) 33, S17–S23
Johnston et al. Circadian Rhythms, Metabolism, and Chrononutrition in Rodents and Humans REVIEW FROM ASN EB 2015 SYMPOSIUM
Relation between ADHD and a disturbed circadian rhythm
ADHD (Attention Deficit Hyperactivity Disorder) is a neurodevelopmental condition with increasing prevalence affecting around 7-8% of children. It often continues into adulthood. Roughly two thirds of children diagnosed with ADHD use medication for their condition.
Research has shown circadian rhythm disruption in adult ADHD with delayed sleep onset, phase delay of dim light melatonin onset (DLMO) and an association with evening chronotype. A circadian phase disturbance contributes to both subjective and objective dysfunction in adult ADHD.
Insomnia amongst adults and children with ADHD is common, which is directly related to a disturbed circadian rhythm. About half of the children suffering from insomnia receiving melatonin also use ADHD medication. An increase in prescription of melatonin has been reported.
Bright sunlight is known to enhance and reinforce our own natural circadian rhythms. Emerging research on light therapy has shown beneficial effects on circadian disruption and alleviation of ADHD symptoms.
One study found
Another study found
These promising study results highlight the positive effects of a normalised circadian rhythm for persons with ADHD, where BCL and dynamic lighting can be extra beneficial.
Coogan and McGovan A systematic review of circadian function, chronotype
and chronotherapy in attention deficit hyperactivity disorder ADHD Atten Def Hyp Disord (2017) 9:129–147
Fargason et al Correcting delayed circadian phase with bright light therapy predicts improvement in ADHD symptoms: A pilot study Journal of Psychiatric Research 91 (2017) 105-110
Rybak et al An Open Trial of Light Therapy in Adult Attention-Deficit/Hyperactivity Disorder J Clin Psychiatry 2006;67:1527–1535
Furster and Hallerbäck The use of melatonin in Swedish children and adolescents—
a register-based study according to age, gender, and medication of ADHD Eur J Clin Pharmacol (2015) 71:877–881