Losing sleep over sleep deprivation? On average, Americans live for approximately 75 years, of which they spend about 25 years sleeping. There is perhaps no other single activity that preoccupies a human life as much as sleep does.
Sleep is a universal trait in the animal kingdom and is likely an evolutionary survival tool. It is speculated that sleep offers adaptive inactivity to ensure that species are not active and exposed to predators when they are most vulnerable. Other theories include energy conservation theory, restorative theory (time for the brain to repair itself) and brain plasticity theory (sleep correlated to bodily changes such as growing children needing more sleep than grown adults). Although there is no consistent empirical data to pin any of these theories to the evolutionary purpose of sleep, biological truth about the purpose of sleep is likely hidden among all of these theories. What we do know, is that sleep is not, however, a state of unconsciousness as envisioned in the early days, but is a highly metabolically active state.
How sleep effects the brain’s circadian clock:
Much like the body regulates activities such as eating, drinking and breathing, sleep is regulated by the brain’s circadian clock (the cycle that tells us when to sleep, rise, eat, etc.). It is estimated that between 8-15% of the gene expression is circadian.
Among other biological activities, growth hormones are secreted while testosterone and thyrotropin are inhibited during sleep. Our circadian clock receives feedback signals from the liver, heart, pancreas, kidneys, lungs, intestines, and even from the skin and lymphocytes. A disruption in circadian rhythm from sleep deprivation can offset the “feedback clocks” in all of these major stakeholders of health. It must then be of no surprise, that a significant body of emerging evidence indicate that sleep deprivation is a risk factor for obesity, type 2 diabetes and hypertension, and an independent predictor of stroke, coronary heart disease (CHD) and cardiovascular disease (CVD).
The link between sleep deprivation and obesity:
Sleep deprivation corresponds to decreased activity in the frontal lobe, which controls decision making, and increased activity in the amygdala, which senses fear. Together, these changes make a person vulnerable to binge eating. (Let’s say in this case, a “fear” of hunger combined with poor decision making may mean indulging in a nice glazed donut sitting on the kitchen counter.) Now, view this in the context that due to the circadian rhythm, glucose tolerance is lower in the evening and at night than in the morning. For a person struggling to initiate sleep, a perfect storm of desire to eat is presented at a time when the body is predisposed to a state of poor energy metabolism. The circadian dependence on glucose tolerance is a key reason why late eaters lose less weight than early eaters when controlled for caloric consumption.
Sleep deprivation and metabolic disorders:
Multiple studies have linked sleep deprivation to metabolic disorders. Based on meta-analysis from many studies across continents, and based on the known biochemistry of circadian rhythm and sleep, a Japanese group (Nagai et. al.,) proposed a mechanism for correlation between sleep deprivation and the onset of diabetes, Coronary Artery Disease (CAD), and hypertension. (Interesting fact: Japanese vocabulary has a word for “death from being overworked”, which loosely translates to “karoshi”.) The mechanism evokes the role of psychological and environmental stress in dysregulating hypothalamic activity causing reduced secretion of melatonin. This causes sleep deprivation and increased sympathetic nerve activity (when the body feels the need to be alert) which in turn increases the blood pressure, when per circadian clock, blood pressure should be at its lowest. Sleep deprivation increases cortisol and lowers testosterone. These changes together cause elevation in insulin and glucose, and predisposes the individual to insulin resistance, obesity, and diabetes mellitus. In the evenings following sleep deprivation, both the sympathetic nerve activity and blood pressure are elevated, and together, along with other biochemical changes, a stage is set for the onset of coronary artery disease.
But, what does it mean to be sleep deprived?
One can be deprived of quantity and/or quality of sleep. The National Sleep Foundation recommends that adults get 7-9 hours of sleep while children require a longer quantity of sleep (8-10 hours for a teenager, 9-11 hours for elementary aged children, and 12-15 hours for an infant). Significantly less (or more) than these quantities of sleep would constitute a sleep disorder.
Shortened sleep duration is defined as less than six hours of sleep while less than four hours of sleep at night is considered extreme sleep deprivation. The National Sleep Foundation also defines quality of sleep as sleeping more time than not while in bed (at least 85 percent of the total time) and:
- Falling asleep in 30 minutes or less.
- Waking up no more than once per night.
- Being awake for 20 minutes or less after initially falling asleep.
The symptoms of insomnia include difficulty initiating sleep, difficulty maintaining sleep, early-morning awakening or non-restorative sleep.
Another well-known condition that causes sleep deprivation is sleep apnea; a common disorder in which you have one or more pauses in breathing or shallow breaths while you sleep. In its most common form, obstructive sleep apnea, the airway collapses or becomes blocked during sleep. This causes shallow breathing or breathing pauses. It is well documented that the peak frequency of adverse cardiovascular events such as MI occur in the morning, and sleep apnea is suspected to be linked to this phenomenon. The good news is that sleep apnea can be well managed with help from your healthcare provider using a continuous positive pressure airway (CPAP) device which requires a prescription.
If you’re struggling to get a good night’s sleep, try some of these suggestions from sleep experts:
- Get regular physical activity, but don’t do it right before bed because that gets your adrenaline pumping and can keep you awake.
- Limit alcohol consumption to one drink per day for women, and two drinks for men; too much alcohol interferes with sleep.
- Avoid caffeine before bed.
- Develop a pre-bedtime routine such as taking a warm bath, dimming the lights or having some herbal tea.
Reducing sleep deprivation by optimizing work-life balance and taking steps to reduce stress in life, and if necessary seeking help from your medical provider to improve your circadian alignment, can pay sound dividends in terms of good metabolic health and an efficient mind.
In good (metabolic) health,
Hari