Dear Doctor: While my wife and I were working in the garden, she got dizzy and couldn't understand what I was saying. It went away after a few minutes, but I took her to the ER anyway. The doctors said she had a TIA. What is that, and is it dangerous?

Dear Reader: Your wife experienced a transient ischemic attack, or TIA. Also known as a mini-stroke, a TIA happens when part of the brain is temporarily deprived of blood flow.

You were right to seek immediate medical help. The symptoms of a TIA and those of a major stroke, which is the fifth-leading cause of death in the United States, are quite similar. And though the effects of a TIA are temporary -- that's the "transient" in the name -- that doesn't mean they're harmless.

First, let's talk about what's going on.

Ischemic strokes occur when a blood vessel in the brain becomes blocked, often by a blood clot. As a result, the part of the brain that is fed by that vessel is starved of blood. Since blood carries oxygen, which is vital to survival, it takes just a few minutes for brain cells to begin to die.

Unlike in a major ischemic stroke, where the blockage persists and damage can be permanent, a TIA resolves quickly. Sometimes it takes just a few minutes, and sometimes the effects can last up to 24 hours. When the TIA is over, the person feels normal again.

Symptoms of a TIA include the dizziness and cognitive lapse that your wife experienced. Additional symptoms may be a sudden headache, impaired vision, numbness or weakness in the face or limbs, garbled speech, and loss of balance and coordination.

The federal Centers for Disease Control and Prevention classify a TIA as a medical emergency. Although impairment due to a TIA is temporary, the event itself is a warning sign that needs to be addressed. A person who has experienced a TIA is at increased risk of a full-blown stroke, particularly in the first few days after the attack. However, with prompt treatment, as well as certain lifestyle changes, you can decrease the chance of a future stroke.

Your wife should see her primary care physician to discuss what happened and to begin treatment. This typically includes taking aspirin, a blood thinner that makes your platelets less likely to clump together. Aspirin should be initiated and continued under a doctor's supervision.

The good news is that your wife can also make some simple lifestyle changes to decrease her risk of another episode:

-- Keep blood pressure under control.

-- Don't smoke, and avoid secondhand smoke.

-- Maintain a healthy weight.

-- Eat plenty of fresh fruits and vegetables.

-- Exercise regularly.

-- Avoid stress.

-- Get enough sleep.

-- Limit alcohol.

Even better news: Every one of these suggestions will make you healthier, too.

(Eve Glazier, M.D., MBA, is an internist and assistant professor of medicine at UCLA Health. Elizabeth Ko, M.D., is an internist and primary care physician at UCLA Health.)

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o Media Relations, UCLA Health, 924 Westwood Blvd., Suite 350, Los Angeles, CA, 90095.)

Dear Doctor: Some women, and juries, say that talc causes ovarian cancer, but doctors say it doesn't. Where's the evidence either way?

Dear Reader: Talc is a mineral composed of magnesium and silicate. Talcum powder, commonly known as baby powder, was first marketed by Johnson & Johnson in 1894. It was first used, and is still used, to prevent diaper rash. The concern regarding ovarian cancer is that talc may pass into a woman's uterus and then move up the fallopian tubes during menses. In fact, talc particles have been found in the fallopian tubes of women who have used talcum powder on sanitary napkins or pads.

The suggestion that talcum powder may lead to ovarian cancer first came from case-control studies. The largest of these was a combined analysis of eight different studies that compared 8,525 women (cases) who had ovarian cancers and 9,859 women (controls) who did not. In the studies, researchers asked women if they had used talcum powder in the genital area previously and how frequently. The authors concluded that the use of genital powder was associated with a 20 to 30 percent increase in some types of ovarian cancer.

One problem with that analysis is that some powders contain cornstarch, not talc. The other problem is that of recall bias. Women with ovarian cancer may report previous use of powders because they believe there may be a link between the powder and their ovarian cancer. Further, the authors did not find any dose response associated with powder use, meaning that they did not find a link between greater amounts of powder and ovarian cancer.

Other case-control studies have come up with similar conclusions. Based on such data, many lawsuits have contended a link between talcum powder and ovarian cancer. Two of these lawsuits have led to judgments of $72 million and $55 million against Johnson & Johnson.

One difficulty with analyzing statistical links to ovarian cancer is that the disease is somewhat rare; over her lifetime, the average woman has only about a 1 percent chance of developing it. To truly study a potential link between ovarian cancer and talcum powder, you would need large studies. You would also need prospective studies. A prospective study in this case would assess talcum powder use and follow women over time to see if they developed ovarian cancer.

Several studies have attempted to do this. The Nurses' Health Study included 78,683 women followed for nearly 13 years. These women were asked about their use of talcum powder and, over the course of 13 years, 307 cases of ovarian cancer were found. Note that researchers did not find talcum powder to be associated with ovarian cancer, although they did find a 9 percent increase among women who used talcum powder.

The Women's Health Initiative included 61,000 women followed for more than 12 years. In that study, researchers also found a minimal increase in ovarian cancer, but not a statistically significant one. The biggest problem with these prospective studies is that they need to be even larger and longer.

It's possible that there is a minimal increase in ovarian cancer among menstruating women who use talcum powder. However, this may have more historical relevance than topical relevance because fewer women are using talcum powder today than in years past. If you do use a genital powder, cornstarch powder would be a good alternative to talc.

(Robert Ashley, M.D., is an internist and assistant professor of medicine at the University of California, Los Angeles.)

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o Media Relations, UCLA Health, 924 Westwood Blvd., Suite 350, Los Angeles, CA, 90095.)

Dear Doctor: I recently added running to my weight-loss program. Not only do I feel better, but the pounds are also coming off faster. However, I keep reading that running is bad for my knees, so it makes me wonder -- am I making a mistake?

Dear Reader: We're happy to reassure you that running, when done properly, is not bad for your knees. In fact, a number of recent studies suggest the opposite is true.

In addition to a lowered risk of stroke and heart attack, runners in the studies had lower rates of osteoarthritis than the non-runners did. And thanks to the runners' general level of fitness, their chosen form of exercise was seen as beneficial to maintain joint health.

The idea that running is bad for your knees is one of those myths that just won't go away. It sounds like common sense -- you hit the ground with a certain amount of force as you run, so over the course of a few miles (or quite a few, if you're a distance runner) your knees must take a beating. But numerous studies conducted over the last decade have repeatedly shown that's not so.

Researchers found no correlation between running and osteoarthritis, also known as OA. Sure, a percentage of the participants in the long-term studies did develop OA. However, when scientists looked closely, it turned out that running was not a risk factor. Instead, obesity, family history, advanced age and previous muscle or joint injury proved to be the real predictors of future osteoarthritis.

In fact, it turns out that people who exercise -- and this includes short- and long-distance runners -- get extra protection against OA. As we mentioned earlier, runners' muscles are more toned and therefore reduce the pressure the joints are asked to bear. Add in the fact that runners tend to have a lower BMI -- that's body mass index, a measure of fitness calculated by height and weight -- and researchers agree that running is good for you.

Before you race out the door, though, there are caveats. If you have injured yourself in the past, whether a muscle, cartilage or ligament, you may indeed be at risk of further damage. But if you're a healthy individual without a history of injury, running is a good way to boost your weight loss -- and, as you also noticed, your mood.

A few things to consider as you add regular running to your routine:

-- If you're over 40 years old or more than 20 pounds overweight, it's probably wise to talk to your primary care physician about your plan to run regularly.

-- Proper training takes time, probably longer than you imagine. Don't think in terms of miles at the beginning. Instead, pick a time interval -- 10 or 20 minutes to start -- and mix running with walking as you ease into your new routine.

-- Get good shoes and insoles. It makes all the difference to the alignment of your leg, which helps protect your knees. And be sure to replace your running shoes before they wear out.

-- Never run when injured. Ever. Sharp pains, sudden pains or pains that are on one side of the body but not the other can be warning signals.

-- Yes, you really do need that day (or two) of rest per week to stay injury-free.

(Eve Glazier, M.D., MBA, is an internist and assistant professor of medicine at UCLA Health. Elizabeth Ko, M.D., is an internist and primary care physician at UCLA Health.)

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o Media Relations, UCLA Health, 924 Westwood Blvd., Suite 350, Los Angeles, CA, 90095.)