Do without sleep now and make up for it later. It's a pretty common sleep strategy for adults with busy lives and demanding schedules that crowd out sufficient time for sleep on a daily basis. We've seen evidence in recent years that this strategy -- of running up a sleep deficit and attempting to catch up on sleep at a later point -- meets with limited success. In recent years, research has indicated that the effects of insufficient sleep can't be fully remedied by recovery sleep. And for many people who work especially long hours or irregular and nighttime hours in shift work, and for others who suffer from chronic sleep deficiencies through sleep disorders, sleep loss can become too large and too frequent a debt to surmount.
New research suggests that the consequences of chronic insufficient sleep are less reversible than previously understood and may involve lasting damage to the brain. Researchers at the University of Pennsylvania's Perelman School of Medicine and China's Peking University studied neural activity in mice under different levels of sleep loss. They found prolonged periods without sleep led to impaired neurological cell function and to the death of brain cells. This is some of the first evidence to indicate irreversible damage to the brain linked to insufficient sleep.
Scientists put mice on a rotating sleep routine, including periods of normal rest, short periods of wakefulness and also extended periods without sleep. The sleep model was designed to mimic a human shift worker's sleep routine. After each sleep period, researchers conducted neurological examinations looking for evidence of damage and altered function. Researchers were particularly interested in the area of the brain known as the locus coeruleus (LC). LC neurons participate in a wide range of important neurological functions, including regulation of arousal, attention and wakefulness, as well as memory, emotional responses and cognitive function. Examining the mice after different degrees of sleeplessness, researchers found significant changes to the health and function of this area of the mice brain. They discovered that while LC neurons in mice were able to cope effectively through short-term periods of sleep deprivation, periods of extended wakefulness brought diminished function and eventual loss of brain cells:
• Short-term sleep loss in mice elicited a protective response from LC neurons. Subjected to short periods of sleep deprivation, LC neurons increased production of a protein that helps protect the brain cells from damage.
• Short-term sleep loss also spurred antioxidant activity in LC neurons, another protection against cell damage and stress.
• Under periods of prolonged sleep loss, LC neurons lost the ability to generate these protective responses. After several days of a sleep pattern that looked like a shift workers sleep schedule and included periods of prolonged wakefulness, LC neurons showed diminishing levels of the protective protein.
• Under these conditions of extended and recurring sleep loss, LC neurons in mice began to die. Researchers found mice lost 25 percent of LC neurons after several days of the shift worker sleep routine.
We don't know yet that these effects of recurring or chronic sleep deprivation observed in mice will present themselves similarly in humans. That's a next step for researchers to explore, along with establishing more precisely the degree of sleep loss that might expose the brain to risk for this type of lasting damage. But these results are troubling, and strongly caution against the idea that chronic sleep loss can be recouped -- that we can continually repay ourselves a sleep debt in full and without harm or negative consequence.
Other recent research has also highlighted the damaging effects of insufficient and poor quality sleep on the brain:
• Swedish researchers studied the effects on the brain of a single night of total sleep deprivation. Their research, conducted with 15 healthy young men, revealed that after a single night of total sleep loss, blood concentration in brain cells rose by 20 percent, to levels that can signify neural damage.
• A recent study of Gulf War veterans found a link between poor sleep quality and reduction in brain tissue volume. Deterioration of brain tissue occurred in widespread areas across the brain, including the brain's frontal lobe. Researchers established that this link between diminished brain tissue volume and poor sleep existed independent of soldiers' exposure to other risks to brain health, including trauma and physical and mental illnesses including PTSD.
The current research delivers sobering news but also opens some important pathways for future inquiry, ones that may lead to new and better treatments for sleep problems and perhaps for other neurodegenerative diseases. This research provides important new insight into how at least one part of the brain works to protect itself against short-term sleep loss -- and that is knowledge that may be helpful in creating new treatments for people who struggle with chronic sleep insufficiency, including many of the 15 million shift workers in the United States and millions more around the world.
Researchers also intend to further examine the sleep-related damage to LC neurons and a possible relationship to neurodegenerative diseases including Alzheimer's and Parkinson's disease. There is evidence that damage to this area of the brain may speed the development of these diseases. Further study of the effects to this area of the brain as a result of sleep loss may help scientists identify people who -- by age, health, or lifestyle -- are at elevated risk for this type of neural damage.
This is yet another powerful reason to establish a routine of high-quality, plentiful sleep -- and to avoid the cycle of sleep debt. In doing so, you may protect your brain from damage that can't be undone.
Michael J. Breus, PhD
The Sleep Doctor™