Can I do anything to prevent nightmares?

DEAR DOCTOR K: Is there anything I can do to stop having terrible nightmares? They scare me, and ruin my sleep.

DEAR READER: There may be something you can do. The first thing you should know is that everyone has nightmares occasionally. That includes yours truly. Just as we don't really know why we sleep, we don't really understand nightmares. We also don't know why some people are more likely to have them.

Would I be better off with hip resurfacing or a hip replacement?

DEAR DOCTOR K: My hip has bad arthritis, and my doctor says I need either a hip replacement or something called "hip resurfacing." Which one is best?

DEAR READER: I once had to ask myself that same question, when my right hip became so painful from arthritis that something needed to be done. Let me first explain what each type of surgery is, and then how to think about the choice between them.

Do all cases of DCIS breast cancer need aggressive treatment?

DEAR DOCTOR K: I have been diagnosed with ductal carcinoma in situ. My doctor wants me to have surgery. But recently I read about a study that said not all women with this type of breast cancer even need to be treated. Can you help clear this up?

DEAR READER: Ductal carcinoma in situ (DCIS) is a type of breast cancer. In DCIS, the cancerous cells are contained within the breast's ducts (which carry milk to the nipple) but have not invaded surrounding tissue.

Does prediabetes put me on an irreversible path to Type 2 diabetes?

DEAR DOCTOR K: After years of normal blood sugar levels, I'm suddenly in the prediabetes range. Am I on an irreversible path to Type 2 (adult-onset) diabetes?

DEAR READER: No, you're not, but you're facing a challenge. Prediabetes is an early warning signal: You are at higher risk for developing diabetes. But diabetes is not inevitable. In fact, we know more about how to reduce the risk of getting Type 2 diabetes than we know about preventing most other major diseases. There are several things you can do to reverse course.

Does standing more really make a difference to your health?

DEAR DOCTOR K: Several of my colleagues have switched to standing desks. Does standing really make that much of a difference to your health?

DEAR READER: Research suggests that the more we sit, the more we're likely to develop heart disease and other illnesses, including diabetes and cancer. Whether it's sitting at the computer to get some work done or on the couch watching TV, too many hours spent on our bottoms increases the risk of dying from any cause -- even if you exercise regularly.

Will a pertussis booster shot for me help protect my grandkids from whooping cough?

DEAR DOCTOR K: My son says that if I get a booster shot for pertussis, it will help protect his kids from getting whooping cough. That seems far-fetched to me.

DEAR READER: It's not far-fetched. Even if you were immunized against pertussis (the bacteria that cause whooping cough) as a child, you may need a booster shot. Why? Because pertussis is highly contagious, and without a booster shot you are at some risk for getting it. And if you get it, you could pass it on to your grandkids.

Should I get a flu vaccine this year even if last year’s vaccine didn’t prevent me from getting the flu?

DEAR DOCTOR K: I got the flu vaccine last year and still got the flu. Should I even bother with the flu vaccine this late?

DEAR READER: Yes, you should, but don't expect perfect protection this year, any more than you should have last year. Vaccines contain fragments of three or four strains that are predicted to dominate during the coming flu season. Different strains of the virus circulate each flu season (October-May).

Should I get a c-reactive protein test to check for heart disease?

DEAR DOCTOR K: Both my parents had heart disease, so I'm worried I might get it. A friend said I should get a CRP test, but my doctor hasn't ordered one. Should I ask him about the test?

DEAR READER: The answer is controversial. For full transparency, I should say that this test was developed and studied by a colleague of mine at Harvard Medical School, and revenue from the test comes to my colleague and to the hospital where I practice.

How much sleep do I really need?

DEAR DOCTOR K: Between my young kids and a full-time job, I'm lucky if I manage five hours of sleep per night. My husband says I'm running on empty. How much sleep do I really need?

DEAR READER: You're not alone. According to the Centers for Disease Control and Prevention, the percentage of adults sleeping fewer than six hours per night has increased by 31 percent since 1985. I spoke to my colleague Dr. Stuart Quan, professor of sleep medicine at Harvard Medical School. He noted the many negative consequences of insufficient sleep.

What are the risks and benefits of mammograms?

DEAR READERS: In yesterday's column, I answered a question from a 47-year-old woman who had never had a mammogram and wondered if she should have one. She had heard that one group of experts -- the American Cancer Society (ACS) -- had recently changed its recommendations on this issue.