Like George, many people who are overweight also have elevated blood pressure, cholesterol, blood glucose and insulin resistance. This combination of problems is more than just coincidence. It is called Syndrome X or ‘Metabolic Syndrome, ‘and is very common, affecting a quarter of the population. People with metabolic syndrome are four times as likely to develop Type 2 diabetes. The prevalence of diabetes has doubled over the past 20 years and now affects more than 8% of Canadians. Diabetes is very serious and a major cause of heart disease, kidney failure and blindness.
Diet and exercise can contribute to achieving target blood glucose, cholesterol and blood pressure levels, but for many people this is not enough. Sleep may be the missing link to more effective diabetes management.
George’s long-suffering wife has put up with his loud snoring for years. However, the pauses in his breathing followed by snorting and gasping for air really worry her. Sometimes, she lies awake just so she can nudge him to start breathing again. George’s daytime fatigue and irritability are also a problem. He gets sleepy in the afternoon at work, and usually has to nap when he gets home. One day, an article in a magazine about obstructive sleep apnea (OSA) catches his wife’s eye. It describes George perfectly.
Apnea means ‘no breathing.’ A visit to the doctor followed by an overnight sleep study at the local sleep lab confirms George’s severe OSA. The study shows that during sleep, the flow of air to George’s lungs was being repeatedly shut off more than 40 times per hour. The blockages in airflow were caused by the collapse of his upper airway at the back of the throat when he sucked in his breath. Each time a blockage occurred, the oxygen level in his blood dropped from a usual level of 95 per cent down as low as 70 per cent. The drop in oxygen triggered the emergency “fight or flight response” to momentarily wake him up to breathe. The awakenings lasted only three to 15 seconds. Although they were usually not long enough for George to remember that he was awake, they were frequent enough to significantly interfere with the quality of his sleep. This severe sleep disturbance left him feeling tired and sleepy the next day.
The ”fight or flight response” not only wakes him up to breathe. The surge of adrenalin also stresses the cardiovascular system, raising the blood pressure and heart rate. It also raises the blood glucose. Studies show that half of people with OSA develop high blood pressure. Those with diabetes have more difficulty controlling their blood glucose. Decades of jump-starting the cardiovascular system, often hundreds of times per night, significantly increases the risk of heart attack, heart failure and stroke. In fact, 25 to 30 per cent of patients with high blood pressure, heart disease or stroke have OSA contributing to their health problems.
The medical term ‘obesity’ refers to people who are significantly overweight. Central obesity (fat around the middle) is a common feature of both Type 2 diabetes and OSA. Being overweight contributes to narrowing of the airway making a blockage more likely. Eighty per cent of people with OSA are obese. OSA affects between 9 and 38% of the population. Due to the high prevalence of central obesity in Type 2 diabetes, OSA in people with diabetes is closer to 54%. OSA appears to be a common factor contributing to the fatigue and cardiovascular complications of diabetes.
Even though he had felt tired for a number of years, George is shocked to learn he has a severe sleep disorder. He always thought he was a good sleeper, able to fall asleep whenever he wanted to. What he did not know was that people who fall asleep ‘before their head touches the pillow,’ or who can easily nap during the day, are abnormally sleepy. It may mean they are simply not getting enough sleep, or it may mean the person has a sleep disorder.
Once George’s OSA is treated, his blood glucose and blood pressure begin to meet his target levels. He is no longer tired and sleepy during the day. He can also follow his diet more easily because the craving to snack for energy is gone. Now that he is able to exercise on a more regular basis, he begins to lose weight.
Joanne is a 37-year-old office worker who has had Type 1 diabetes for 15 years. Her blood glucose has been poorly controlled. For the past two years, she has had difficulty getting her legs comfortable and keeping them still. She notices it most when she sits for long periods or lies down in bed. Moving her legs or walking around relieves the sensation, but only for a few seconds or minutes. As a result, she has great difficulty getting to sleep and staying asleep. Her husband notices that she kicks and twitches repeatedly throughout the night. Joanne has lost much of her motivation and enjoyment of life because she is too tired to do anything.
The symptoms Joanne is experiencing while awake are called Restless Legs Syndrome (RLS). It affects 15 percent of the general population but is much more common in people with diabetes and those with kidney failure on dialysis. This condition is a real torture and causes insomnia. The symptom her husband notices when she is sleeping is Periodic Limb Movement Disorder (PLMD). Her legs kick or twitch every 30 to 90 seconds during periods of the night. The brain may wake up momentarily with these movements, so PLMD can cause significant sleep disturbance. People with this problem are often tired and sleepy the next day. Eighty per cent of people with RLS have PLMD. Joanne’s doctor tells her that she has early peripheral neuropathy, a nerve disease that leads to reduced sensation in the lower limbs. It is caused by prolonged high blood glucose levels that can damage the tiny blood vessels in the nerves and interfere with nerve function. When Joanne’s blood glucose is brought under better control, her symptoms subside. She feels much more rested in the morning and is no longer sleepy during the day. Fortunately, better control of her blood glucose has improved her sleep. Joanne’s doctor reassures her that if she has more problems, there are medications that can provide good relief for RLS and PLMD.
In Joanne’s case, diabetes was indirectly affecting her sleep. Most people with diabetes are aware of the increased thirst and need to pass urine at night associated with elevated blood glucose. For others like George, poor sleep itself is affecting their diabetes. There are several reasons why sleep is a key part of managing diabetes.
Studies have shown that chronically sleep-deprived people with Type 2 diabetes have much more difficulty controlling their blood glucose. This is caused by a significant increase in insulin resistance. The insulin is less effective at triggering the cells of the body to take glucose out of the blood into the cell for energy. As a result, the body must secrete more and more insulin to control the blood glucose. Eventually, the body cannot produce enough insulin and the blood glucose rises above normal, resulting in diabetes. Excess levels of insulin also encourage the body to store glucose as fat rather than burning it for energy. The risk of obesity rises.
People with diabetes sleep almost two hours less and report that their sleep quality is worse than the average person. Studies have shown that the worse their sleep, the higher is their HbA1c (glycosylated hemoglobin). Elevated HbA1c indicates that blood glucose has likely been under poor control over the previous three months.
Even people who are simply overweight report more sleep disturbance and less sleep than average. Poor sleep may be the missing link in overweight people who have trouble losing weight despite their best efforts with diet and exercise. This is important since obesity is a significant risk factor for developing Type 2 diabetes.
Poor sleep may reduce the production of three other hormones important in maintaining normal body weight. Growth hormone and testosterone are two hormones released primarily during deep sleep early in the night. These hormones are necessary for maintaining or building muscle mass with exercise both in men and women. Muscle cells burn twice the calories than fat cells, even at rest. You can burn only a few hundred calories of energy per hour of exercise. During the rest of your day and night, the resting metabolism is a key factor in burning enough calories to achieve and maintain ideal body weight. Resting metabolism is largely related to muscle mass. Building muscle mass with exercise is dependent on growth hormone and testosterone which in turn are dependent on an adequate quality and quantity of sleep. Thus, sleep is critical for controlling your weight.
One of the changes that occurs with age is a reduction of growth hormone and testosterone. This is partially due to reduced amounts of deep sleep as we age. Many people blame age as the cause of the loss of these hormones. However, it is likely that poor sleep habits over a lifetime are just as much to blame. When researchers look at healthy active men in their retirement years, both their sleep quality and production of growth hormones and testosterone are much closer to those of younger men than their ailing, inactive and overweight peers. Many people have difficulty controlling their weight as they get older despite following good diets and remaining active. This may be largely due to poor sleep.
In fact, many hormonal and metabolic changes seen in aging and Type 2 diabetes are also seen in people getting inadequate sleep. Other hormonal changes seen in aging, diabetes and sleep deprivation are elevations of the stress hormones, cortisol and adrenalin. It is likely that poor sleep accelerates the deterioration of our body seen in aging. This is not surprising considering that much of our healing, recovery of day-to-day wear and tear, and recharging of our energy occurs during deep sleep.
Another important hormone in obesity is leptin which is produced by the obesity gene. It triggers feeling full after meals, making you less likely to overeat. It also promotes the burning of fat and weight loss. Production of leptin peaks at night and is decreased by sleep deprivation. Evidence suggests reduced levels of leptin may lead to obesity. Chronic sleep deprivation may also contribute to the body becoming resistant to leptin.
Reducing sleep quality and quantity causes hormonal changes that contribute to weight gain as well as developing metabolic syndrome and Type 2 diabetes. Poor sleep makes diabetes worse. People with diabetes are prone to sleep disorders such as obstructive sleep apnea which increases the risk of developing hypertension, heart disease and stroke. These changes are also seen in aging. It is likely that the effects of aging are aided and abetted by poor sleep.
Obesity and Type 2 diabetes are rapidly increasing in our society. The occurrence of sleep disorders and sleep deprivation is also very high. The National Sleep Foundation in the US found that 58 per cent of people suffer from sleep disorders. As well, 66 per cent get less than the recommended eight hours of sleep per night. Although a number of factors contribute to diabetes, including poor diet and lack of activity, inadequate quantity and quality of sleep appear to be just as important.
Along with healthy diet and exercise, good sleep is essential for blood glucose control, managing diabetes and obesity. Healthy sleep helps reduce the complications of diabetes and heightens overall well-being. If you are concerned about your sleep or have symptoms mentioned in this article, talk to your doctor.
WRITTEN BY: Ronald Cridland, MD, CCFP, Diplomate, American Board of Sleep Medicine, who practices in Kelowna, British Columbia.