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Sleep problems, heart disease often in bed together

(This article was first printed in the January 2007 issue of the Harvard Heart Letter. For more information or to order, please go to http://www.health.harvard.edu/heart.)

Sleep seems to be such a serene way to replenish energy and restore the mind. For your heart, blood vessels, and immune system, though, it’s anything but peaceful. There are periods of calm, to be sure, but they are rudely interrupted by abrupt spikes in blood pressure and heart rate. Blood flow through the heart and brain varies widely during sleep, as do electrical activity in the heart, the elasticity of blood vessels, and the tendency of blood to clot. And all of this activity is just part of a normal night’s sleep.

Researchers are just beginning to reveal the two-way street between sleep and heart disease: Poor sleep can interfere with the heart, and heart disease can disturb sleep.

Healing sleep

A century ago, the average American slept 9–10 hours a night, with sleep cycles linked to sundown and sunup. Electric lights extended our “day,” while work, television, the Internet, and other distractions have chipped away at sleep. Today, we average just under 7 hours a night; about one-third of us make do with 6 hours or fewer.

Our bodies aren’t like cars or computers that work fine whenever they are turned on. We have an internal clock that governs the body’s systems. Light helps set this clock. So does sleep. Too little of it can throw off the clock and disturb the intricately timed release of hormones and other chemical signals, as well as cause fatigue and daytime drowsiness. Uncoordinated hormonal signals, in turn, can affect many systems in the body. Poor sleep has been linked with high blood pressure, atherosclerosis (cholesterol-clogged arteries), heart failure, heart attack and stroke, diabetes, and obesity.

Inflammation may be a thread that ties these together. Poor sleep increases levels of C-reactive protein, interleukin-6, tumor necrosis factor-alpha, and other substances that reflect active inflammation, the body’s response to injury, infection, irritation, or disease. It is a key player in heart disease, diabetes, and other chronic conditions. Poor sleep also revs up the body’s sympathetic nervous system, which is activated by fright or stress.

The other direction

Sometimes heart disease is a cause of poor sleep. People with heart failure, for example, sometimes wake up at night with trouble breathing, which stems from fluid buildup in the lungs. There’s also some evidence that heart failure leads to central sleep apnea, a breathing problem in the brain’s respiratory center that can awaken a sleeper many times at night. Some people have nocturnal angina (chest pain), which can interrupt sleep. Bouts of atrial fibrillation or palpitations (the sensation of a racing or pounding heart) can also disturb sleep.

Learning to zzz

Improving sleep depends on what’s causing the problem. For some people, it involves adopting better sleep habits. For others, it means coping with the dangerous sleep-time breathing pattern known as sleep apnea.

Get in the habit. Some people sleep effortlessly. Others need to train their internal clock. A few essentials:

• Train your body’s rhythm by going to bed at the same time every night and rising at the same time each day.
• Use your bed only for sleeping or sex. Read, watch television, or work somewhere else.
• If you can’t fall asleep, get up and go to another room. Repeat as needed.
• Go easy on alcohol and caffeine; nix nicotine. Alcohol can make you drowsy, but it disturbs sleep. Caffeine lingers in the body for hours, so go decaf after noon. Nicotine withdrawal, which begins to kick in a few hours after the last cigarette, can wake a smoker from a deep sleep.
• Get some exercise. A brisk walk or other exercise in the late afternoon seems to help with sleep.

Breathe better. Simple snoring is aggravating (to others). Snoring due to sleep apnea is potentially hazardous. People with sleep apnea take shallow breaths or briefly stop breathing hundreds of times a night. The brain, sensing low oxygen and high carbon dioxide, sends an emergency “Breathe now!” signal that makes the person gasp or snort for air. That signal involves the same nerve pathways and hormones that get fired up when you are frightened or under stress (the sympathetic nervous system). Their effects extend far beyond breathing: They can boost blood pressure, provoke disturbed heart rhythms, and reduce blood flow to the brain.

The most common treatment for sleep apnea is a breathing mask that delivers pressurized air from a small pump. Mouth guards that force the jaw forward are also sometimes used to keep the airway open during sleep.

See a specialist

If you aren’t getting enough sleep, you may just need to “set your clock” with better sleep habits. If that doesn’t work, or you are worried about your sleep (or your bed partner’s), tell your doctor. He or she may have some helpful ideas. One of them may be to refer you to a sleep specialist or sleep clinic, especially if you have sleep apnea.

No matter what the cause of your sleeplessness, don’t take the problem lying down. A good night’s sleep is a necessity, not a luxury, for better cardiovascular and overall health.

(This article was first printed in the January 2007 issue of the Harvard Heart Letter. For more information or to order, please go to http://www.health.harvard.edu/heart.)

Harvard Heart Letter If you’re concerned about heart disease, you need expert information and advice you can trust. The Harvard Heart Letter, from Harvard Medical School, is your monthly advisory on the latest developments in heart health, new treatments, prevention, and research breakthroughs. Read more »