What type of mattress helps with lower back pain?

DEAR DOCTOR K: I have chronic low back pain. What type of mattress should I use?

DEAR READER: Considering that we spend roughly a third of our lives lying in bed, this is a very good question. And you'd think medical science would have a very good answer. I asked my colleague, Dr. Jeffrey Katz, professor of medicine and orthopedic surgery at Harvard Medical School, for his thoughts. He noted that there's not a great deal of research on this topic, but a few studies offer some guidance.

Can you explain the connection between snoring and high blood pressure?

DEAR DOCTOR K: I'm a snorer. I read recently that treating snoring can affect blood pressure. Can you explain the connection?

DEAR READER: Severe snoring can be a sign of obstructive sleep apnea (OSA). If you have OSA, then your breathing is blocked temporarily several (sometimes hundreds) of times per night. What happens is that muscles in your upper airway (the back of the throat) relax too much. Normally, these muscles hold your airway open, so that air moves in and out of your lungs without obstruction.

I can’t sleep because I keep waking up to urinate– What can I do?

DEAR DOCTOR K: I'm an older woman in good health, but I can't get a good night's sleep because I keep waking up to go to the bathroom. What can I do?

DEAR READER: "Nocturia" is the medical term for the need to get up frequently to urinate during the night. It's a common cause of sleep loss, especially among older adults. In severe cases, a person may get up as many as five or six times during the night. This can lead to sleep deprivation and daytime fatigue.

Is it OK to let my teenager sleep late on the weekends?

DEAR DOCTOR K: My teenage son likes to sleep in on weekends, often until noon. Is it OK to let him do this?

DEAR READER: I've been asked this question by nearly every parent of teenagers I know. I checked with my Harvard Medical School colleague, pediatrician Dennis Rosen, who confirmed what I've been saying: Letting your son sleep in on weekends isn't doing him any favors.

I fall asleep easily, but wake in the middle of the night. Do you have tips to help me stay asleep?

DEAR DOCTOR K: I fall asleep just fine, but then I wake up around 4 a.m. It's too early to get up, but I can't fall back asleep. Help!

DEAR READER: Practically everyone has sleep problems occasionally. And a lot of people have sleep problems often. Sometimes it's trouble falling asleep. Sometimes, as in your case, it's trouble staying asleep. And sometimes it's just waking up unrefreshed, even though you think you've slept soundly.

What prescription medications can I take to treat my insomnia?

DEAR DOCTOR K: I can't sleep. Behavioral changes haven't helped. Can you tell me about prescription medications for insomnia?

DEAR READER: I typically prescribe sleep medications only for short-term sleep problems. For example, I might prescribe them for a patient who is traveling across time zones or coping with a death in the family. Even then, I prescribe them at the lowest dose and for the shortest possible time. Behavioral changes -- such as going to bed and getting up at the same time each day, not reading or watching TV in bed, etc. -- usually work if you keep at them.

Is a CPAP machine the only treatment option for my sleep apnea?

DEAR DOCTOR K: I have sleep apnea. My doctor has urged me to use a CPAP machine, but it's too uncomfortable. Are there other options?

DEAR READER: Sleep apnea is a condition in which breathing stops or becomes shallower many times each night. Obstructive sleep apnea (OSA) occurs when your upper airway collapses or gets blocked during sleep. These airway obstructions starve your brain of oxygen and stress your cardiovascular system. Untreated sleep apnea increases your risk of high blood pressure, stroke and premature death.

I’ve been falling asleep suddenly during the day — what could be causing this?

DEAR DOCTOR K: I'm 40 years old and in good health. But lately I've been falling asleep suddenly during the day. What could be causing this?

DEAR READER: There are many things that can cause a person to fall asleep suddenly. Your sudden bouts of sleep might be caused by a rapid drop in your blood sugar, a side effect of a medication you're taking, or could result from stress, depression or inadequate sleep at night. Another possibility is narcolepsy.

Does my frequent yawning mean my brain isn’t getting enough oxygen?

DEAR DOCTOR K: I yawn a lot. My friend said this is a sign my brain isn't getting enough oxygen. Is that true?

DEAR READER: Most of us yawn more often in the early morning and late evening. Does it mean you're tired? Bored? Not getting enough oxygen? It turns out that we actually know very little about why we yawn.

How can I help my child fall asleep?

DEAR DOCTOR K: My 8-year-old has trouble falling asleep. Can you give me some practical suggestions that may help?

DEAR READER: The pediatricians here at Harvard Medical School who specialize in sleep problems have given me this advice: To help your child (or anyone of any age, for that matter) fall asleep, you must remove the obstacles that may impede or disrupt his sleep. By doing so, you'll make it much easier for your child to settle down and drift off into a restful slumber.