The Doctor Is In | Column
Deep sleep, also called “slow-wave sleep,” is thought to be the most restorative sleep stage. Going without deep sleep can influence many seemingly unrelated health issues. Having a sleep study may help your doctor diagnose a sleep problem and formulate the proper care plan for you.
Diabetes and sleep
Current research shows a profound decrease in slow-wave sleep has an immediate and significant adverse effect on insulin sensitivity and glucose tolerance. One study found that after only three nights of slow-wave sleep suppression, young healthy subjects became less sensitive to insulin. The decrease in insulin sensitivity was comparable to that caused by gaining 20 to 30 pounds. Although they needed more insulin to dispose of the same amount of glucose, their insulin secretion did not increase to compensate for the reduced sensitivity, resulting in reduced tolerance to glucose and increased risk for Type 2 diabetes. This study provides evidence linking poor sleep quality to increased diabetes risk and the body’s inability to maintain normal glucose control. Since reduced amounts of deep sleep are common in obesity-related sleep disorders, such as obstructive sleep apnea, strategies to improve sleep quality may help to prevent or delay the onset of Type 2 diabetes in populations at risk. For more information on this study, see the University of Chicago Medical Center (2008, January 2). Lack Of Deep Sleep May Increase Risk Of Type 2 Diabetes. Science Daily.
Sleep disturbance and weight gain
Sleep deprivation also increases levels of a hunger hormone, the effects of which may lead to overeating and weight gain. It could explain why so many Americans who are chronically sleep-deprived are also overweight. And it could be part of the reason sleepy college students, new parents and shift workers pack on pounds.
We know the obesity epidemic is because of overeating — big portions, rich food and very little activity — but why do we crave too much of these rich foods? It may be because we are sleep-deprived and unable to curb our appetites. There are more than 80 types of sleep disorders. Sleep apnea is a common and frequently undiagnosed disorder and is linked to obesity.
Sleep deprivation activates a small part of the hypothalamus, the region of the brain that also is involved in appetite regulation. A critical hormone involved in regulating food intake is known as leptin. During sleep, leptin levels normally rise. But leptin levels are also markedly dependent on sleep duration. During periods of sleep deprivation low leptin levels tell the brain there is a shortage of food thereby increasing appetite. Researchers at the University of Chicago School of Medicine found that sleep-deprived men who had the biggest hormonal changes also said they felt the most hungry and craved carbohydrate-rich foods, including cakes, candy, ice cream, pasta and bread. Those who had the smallest hormonal changes reported being the least hungry. Successful treatment of sleep apnea may reduce sleepiness and then motivate people to effectively lose weight, which will in turn help the obesity and the sleep apnea. After losing 10 percent of body weight, consider undertaking another sleep study to determine if further treatment is necessary.
Sleep apnea and stroke
A number of studies have established that in moderate to severe cases of obstructive sleep apnea the risk of suffering a stroke is significantly increased. Almost 75 percent of stroke sufferers have sleep apnea and have worse functional outcomes after a stroke than do patients without apnea. A recent clinical study of 1,475 people found that those with moderate to severe sleep apnea at the beginning of the study were three to four times more likely to have a stroke during the next four years than a comparable group of patients without sleep apnea.
In obstructive sleep apnea, a person’s airway narrows or totally collapses during sleep. They literally can’t breathe while sleeping. As a result, a person stops breathing briefly numerous times throughout the night. They must wake up in order to breathe (but they don’t usually recall these awakenings). The person’s sleep is interrupted often, which may cause excessive daytime sleepiness or even high blood pressure. This repeated fragmentation of sleep patterns keeps them from having normal, restorative sleep. Recent research suggests snoring itself may affect sleep quality and may respond to the same treatments used for apnea.
One reason sleep apnea may increase stroke risk is it has been shown to cause high blood pressure, which is the most common risk factor for stroke. Another possible reason is when a person stops breathing, the lack of oxygen kicks in the body’s “fight or flight” response, which increases adrenaline production. The blood pressure goes up, and blood becomes more apt to clot. The blood clots in the brain cause a stroke. One method of preventing stroke, therefore, is to treat the underlying sleep apnea, of which a major symptom is snoring and daytime fatigue.
Sleep apnea and heart disease
It is estimated about 10 percent of the population have undiagnosed sleep apnea, which may also be an underlying cause of heart disease. One way sleep apnea is linked to heart disease is through its effect on blood pressure. Research has shown apnea patients with normal blood pressure run a risk of developing high blood pressure within four years. Hypertension is a major risk factor in the development of heart disease and stroke.
Apnea patients have higher levels of sympathetic nervous system (SNS) activity during both wake and sleep than patients without sleep apnea. Involuntary functions, such as heart rate and blood vessel constriction, are controlled by the SNS. In people without apnea, there is usually a decrease in SNS activity, and blood pressure falls when sleeping. However, during apnea events, the higher level of SNS activity constricts the blood vessels, while the heart rate also jumps, slamming blood into tight vessels. Blood pressure spikes of up to 250/150 have been seen during apneas.
Sleep apnea patients also have faster heart rates than nonapnea patients, even when awake, but have less variability in their heart rates. This combination of a less variable heart rate and greater variability in blood pressure is an indicator of potential cardiovascular problems.
Lastly, a condition known as central apnea may cause high blood pressure, surges of adrenaline and irregular heart beats. Central apnea occurs without snoring and is not caused by obstruction; rather it is caused by the failure of the brain to signal the body for a breath.
Once again, a method of preventing heart disease is to treat the underlying sleep disorder.
Successful treatment of sleep apnea may play a significant role in preventing hypertension and heart disease. Since a major symptom of sleep apnea is snoring during the night and excessive daytime sleepiness, it is important to establish that you have the correct diagnosis. It is important to talk to your primary care clinician about your sleep problems and take a proactive role. Ask your doctor about your sleep or call the NHCH Sleep Disorders Center at 881-4876 for information.