Cancer is associated with a reduced risk of developing Alzheimer's disease, especially among people treated with chemotherapy.

Q. Doctors always say to get checked out if you have a persistent cough. But how long would a cough have to last before I should see a doctor?

A. Medically speaking, a persistent (or chronic) cough is one that lasts more than three to four weeks. The most common reason for a new cough is an upper respiratory infection from the common cold, which is usually caused by a virus. A cough from an upper respiratory infection could persist for up to two months. In the case of pertussis, or whooping cough, the cough could last for up to three months.

A national panel of experts on disease prevention, the United States Preventive Services Task Force (USPSTF), now recommends that all Americans born from 1946 to 1964 should be tested at least once for hepatitis C virus (HCV) infection. The recommendation follows an earlier call for wider screening for hidden HCV by the Centers for Disease Control and Prevention.

HCV infects the liver. Over time it can cause inflammation, liver damage, and cancer. The infected person's blood can transmit the virus. Past or present intravenous drug users and anyone in the United States who received a blood transfusion before 1992 are at heightened risk. Most of the estimated 3.2 million Americans now infected are unaware they have the virus. Prolonged treatments with antiviral drugs can prevent further liver damage and the need for a transplant.

Sometimes normal eye pressures mask the condition.

Ever get an eye pressure measurement at the eye doctor's office? The doctor directs a probe or a puff of air at your cornea to find out if the pressure inside the eye is elevated, often a major sign of glaucoma. But increased eye pressure isn't always an accurate way to detect the condition. You can sometimes have normal eye pressure and still have glaucoma.

Types of glaucoma

The vision loss of glaucoma is caused by damage to the optic nerve. That's the nerve that sends electrical signals to the brain, which then interprets the signals as images. Nerve damage often results when pressure gets too high because of fluid buildup inside the eye. With the most common type of glaucoma, open-angle glaucoma, damage to the nerve is usually painless and occurs gradually. (With the less common closed-angle glaucoma, people can experience sudden pain and nausea.)

Take the lowest dose of NSAIDs and stop using them as soon as possible.

Blood thinners are usually given to people at risk for developing blood clots from conditions, such as abnormal heart rhythms. Use of these lifesaving medications requires caution with other drugs, especially painkillers called nonsteroidal anti-inflammatory drugs (NSAIDs), such as ibuprofen (Advil) or naproxen (Aleve). But plenty of people take the risk to relieve aches and pains. "Many of the patients who need blood thinners are older and therefore at risk for arthritis, so it's not infrequent for a patient to be on both a blood thinner and an NSAID," says cardiologist Dr. Deepak L. Bhatt, a Harvard Medical School professor.

Men prone to kidney stones should drink plenty of water, get adequate calcium, reduce sodium, limit animal protein, and avoid foods that could make kidney stones more likely to form. Dietary restrictions depend on the stones the person tends to form.

Research we're watching

COPD rates rise in women

Decades ago, chronic obstructive pulmonary disease (COPD) was far more prevalent in men than in women. Now, the gender disparity has reversed. Today, women are 37% more likely than men to have COPD—which includes two lung conditions, chronic bronchitis and emphysema. Women also account for more than half of COPD deaths each year.

According to a recent report from the American Lung Association, the reason for the switch is the increase in smoking rates among women, which started in the 1960s as tobacco companies began to aggressively target our gender (including the 1968 Virginia Slims "You've Come a Long Way Baby" campaign).

Get an exam to pinpoint the cause and then choose.

For dry eyes that keep coming back, you may need special drops to give your eyes' natural lubrication system an extra boost. Proper treatment of chronic dry eye also reduces the risk of infections or damage to the outer surface of the eye.

It appears people with stroke-like symptoms are more likely to develop cognitive problems than people who do not have stroke symptoms.

It appears older adults with diabetes who experience at least one severe bout of low blood sugar may have double the risk for developing dementia. It also appears that low blood sugar occurs more often in people with dementia.