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.

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.

Will a special pillow or other sleep adjustments improve my neck pain?

DEAR DOCTOR K: I tend to have a lot of neck pain. Would it help to buy a special pillow, or make any other adjustments to the way I sleep?

DEAR READER: As with so many things, an ounce of prevention may be worth a pound of cure when it comes to neck pain. And how you sleep at night can make a big difference. Two sleeping positions are easiest on the neck: on your side or on your back. Whichever you prefer, choose an appropriate pillow. If you sleep on your back, choose a rounded pillow to support the natural curve of your neck, with a flatter pillow cushioning your head. You can achieve this by tucking a small neck roll into the pillowcase of a flatter, softer pillow.

How can I overcome insomnia without drugs?

DEAR DOCTOR K: I struggle with insomnia. How can I overcome this problem without drugs or supplements?

DEAR READER: Insomnia is a common problem in which sleepless nights turn into fatigue-filled days. A form of cognitive behavioral therapy (CBT) known as CBT for insomnia, or CBT-I, targets the root cause of insomnia without medication. This short-term talk therapy teaches people to change unproductive thinking and behaviors that get in the way of a good night's sleep.

Do we need to sleep in order to “flush out” our brain?

DEAR DOCTOR K: A friend told me that the reason we sleep is to "flush out" our brain. What is this all about? Is this the reason we sleep?

DEAR READER: Many readers have written asking why we sleep, and we discussed it in yesterday's column. Today we will talk about the recent study that you are asking about, which suggests that one reason we sleep may be to flush out the brain. For those who didn't read yesterday's column, a quick summary. There is evidence that during sleep, our mind and body benefits in several ways. Perhaps most obvious, our muscles get a rest. The fortunate exception is the special muscle that is our heart. We don't want it to quit pumping -- ever!

What does sleep do for us?

DEAR DOCTOR K: Everybody sleeps, but why is that? What does sleep do for us?

DEAR READER: I get this question a lot, and we've talked about it before in this column. There is some new information that is interesting. The honest answer is that we don't know why it is we sleep. We spend about a third of our lives doing it, so nature must have a reason for it. But it's hard to ask nature questions -- or, at least, to get an answer. One possible reason for sleep is obvious: Our muscles may need the rest. However, the heart is a muscle, and it doesn't rest while we sleep, thank goodness. And like our heart, many of our other organs, such as the liver and kidneys, keep working.

Will melatonin supplements help with jet lag?

DEAR DOCTOR K: My wife and I are traveling to Europe in a few weeks, and we're already dreading the jet lag. Do you think melatonin will help?

DEAR READER: Many people find that crossing several time zones makes their internal clocks go haywire. Some small studies have suggested that melatonin can help jet lag if taken a few days before and after travel. Melatonin is a natural substance released by our brain to help coordinate our circadian (day/night) rhythm. This rhythm is disturbed when we travel across time zones. Melatonin is more effective in minimizing the effects on sleep of eastward travel.

How can I get my 9-month-old to sleep through the night?

DEAR DOCTOR K: My 9-month-old is still waking up three to four times during the night. How can I get her to sleep through the night?

DEAR READER: By the time a baby is 4 or 5 months old, he or she is capable of sleeping through the night. We tend to think of "sleeping through the night" as a long stretch of uninterrupted sleep. But in reality, all babies wake up during the night. Some discover their own way of comforting themselves and getting back to sleep. Others must be taught. Different experts recommend different techniques for helping your baby get to sleep and then to sleep through the night.

Are mouth guards an effective treatment for sleep apnea?

DEAR DOCTOR K: I have sleep apnea, and I don't particularly like the CPAP treatment. I've heard that night guards might be an effective alternative. What can you tell me?

DEAR READER: One way or another, getting treatment for sleep apnea is really important. Untreated, sleep apnea increases your risk for high blood pressure, stroke and early death. The airways of people with obstructive sleep apnea narrow as they sleep, and air struggles to get through. People with this condition may breathe shallowly or stop breathing several times an hour.

How can I stop my son from sleepwalking?

DEAR DOCTOR K: My 8-year-old son has started sleepwalking. I'm worried he will hurt himself in his sleep. Is there anything I can do to stop him from sleepwalking?

DEAR READER: A person who is sleepwalking walks or makes other movements while being still largely asleep. A sleepwalker can be difficult to awaken fully and typically has no memory of the episode in the morning. I hope it will ease your worry to know that episodes of sleepwalking are usually brief and harmless.