Sometimes scientific knowledge is slow to displace longstanding beliefs that turn out to be wrong. Health care, being part science and part art, is a particularly fertile area for misconceptions to take root and prosper. Take a look at the following sampling of outdated ideas to see which ones you might still mistakenly believe.

Eating Too Much Sugar Causes Diabetes
This misconception possibly arises from the association of excess body weight with type 2 diabetes, the kind that is common in older adults. However there is no direct link between sugar consumption and the development of diabetes. Diabetes results from a resistance of the body's tissues and organs to the effects of insulin, or from an absolute decrease in insulin production. Since the body requires insulin in order to use sugar, the blood sugar level rises.

A related fallacy is that diabetics cannot eat sugar. According to the American Diabetes Association, judicious amounts of sugar are perfectly acceptable as part of a balanced diabetic diet. Table sugar does not cause blood sugar levels to rise any faster or higher than starches like potatoes and breads.

Older Adults Need Less Sleep
As people age the need for sleep does not decline, but the ability to get a good night's sleep often does. This sleep impairment is more likely the result of health disturbances than aging itself. Various medications, physical illnesses and psychiatric conditions can disrupt sleep. So can certain specific sleep-related disorders such as periodic limb movements in sleep (PLMS), which affects over a third of people over 65.

Elevated Blood Pressure is Normal in Older People
Many people still hold this false belief. Yes, high blood pressure becomes much more common as the years pass, but it is still harmful. Whatever one's age, authorities regard persistent readings above 140/90 as warranting treatment.

Another misconception about blood pressure is that only the diastolic blood pressure (the lower number) matters. In fact, among older people it is systolic hypertension (elevation of the upper number) that causes most damage to the arteries and heart.

Bed Rest Helps You Get Better Faster
It sounds sensible that resting in bed should help you recover from illness more quickly. However, a published review of scientific studies comparing bed rest to early mobilization found that bed rest does not help, and may in fact be harmful.

Lying in bed can contribute to pneumonia, blood clots and muscle weakness. Bed rest can also lead to dizziness and unsteadiness when you do get up, thereby increasing the risk of falls. Better advice is to remain as active as you feel able, just take it easy.

Antibiotics Fight Viral Respiratory Infections
The common cold, influenza, acute bronchitis and sore throat are almost always caused by viruses. Commonly prescribed antibiotics inhibit the growth of bacteria but don't suppress viruses. Despite this fact, innumerable studies have demonstrated gross over-treatment of viral respiratory infections with antibiotics.

Overuse of antibiotics gives rise to treatment-resistant bacteria; this is one of the most pressing public health problems in developed countries. Once-treatable illnesses are increasingly becoming serious threats. The Centers for Disease Control and Prevention estimates that 50 million unnecessary antibiotic prescriptions are written each year, mostly for viral respiratory illnesses.

Cancer Risk is Mainly Determined by Family History
A nationwide poll by the Discovery Channel and the American Cancer Society found that 71% of Americans believe a person's cancer risk has more to do with family history than age. Actually, the opposite is true.

The incidence of most common cancers, including prostate, colorectal, breast and lung cancer, increases with advancing age. Your genetic make-up certainly has some influence, but you should not become complacent just because there has been no cancer in the family.

Heart Disease is a Man's Problem
Many people think of heart disease as something that mainly affects men, and that women should be more worried about disorders like cancer, arthritis or osteoporosis. In fact, more women than men die of heart disease each year. Heart disease causes more deaths in women than the next seven causes combined.

It is true that heart disease tends to develop later in life in women than in men, but it is just as deadly. In women as in men, it is important to maintain a normal body weight, control blood pressure and cholesterol levels, get regular exercise and avoid smoking.

March 2004