What is sundowning?

DEAR DOCTOR K: My husband and I are in our early 80s. Sometimes in the evening he is agitated, confused, and just quite a handful to deal with. The doctor says he has "sundowning." What is it, and is there anything I can do?

DEAR READER: Some older people have trouble concentrating, grow agitated or even confused, and become especially fatigued at the end of the day. This phenomenon is known as "sundowning" because its effects tend to coincide with sunset -- usually occurring in the late afternoon into the evening, then settling down late at night.

What types of joints are available for a knee replacement?

DEAR DOCTOR K: I am going to have my knee replaced. What types of artificial knee joints are available?

DEAR READER: The knee is a joint formed by the bottom end of the thigh bone and the top ends of two bones of the lower leg. When the ends of the bones that form the joint become damaged, they can be removed and replaced. That's total knee replacement, and it is major surgery.

Is it dangerous to sleep too much?

DEAR DOCTOR K: I've heard a lot about the harmful effects of insufficient sleep. But are there any dangers of sleeping too much?

DEAR READER: Over the years we've learned that sleep is important for a variety of reasons. It appears to be vital for forming long-term memories. It also helps you to digest what you have learned the previous day. Sleep promotes concentration and restores energy; it helps to keep your immune system functioning well and to regulate eating patterns.

Is there any way to prevent deep-vein thrombosis during travel?

DEAR DOCTOR K: A friend of mine recently developed a blood clot in his leg after a long flight. I travel a lot for work, so this has me worried. Is there any way to prevent this type of thing?

DEAR READER: A blood clot that forms deep inside a leg vein, known as deep-vein thrombosis (DVT), can cause pain, swelling and redness in the affected limb. But the real threat happens if the clot breaks off and travels to the lungs. Known as a pulmonary embolism, this can lead to sudden death. (I've put an illustration of this process on my website, AskDoctorK.com.)

Any advice to help me stay independent in spite of my arthritis?

DEAR DOCTOR K: Age and arthritis have done a number on my hands. I'd like to continue cooking, eating and dressing independently, but it's getting harder. Any advice?

DEAR READER: Many years ago I had a patient who taught me the importance of what I'm about to tell you. She was in her late 70s, retired, widowed and lived alone. She had been extremely independent all of her life. However, with age her dexterity and fine motor skills had diminished. In addition, the combination of arthritis and a small stroke had made cooking and grooming difficult.

Are epidural injections effective for treating sciatica pain?

DEAR DOCTOR K: I suffer from sciatica, which has caused a lot of pain over the past six month. My doctor has recommended epidural injections, but I hear that they have been disproven. Can you help me sort this out?

DEAR READER: Here's an answer I'm sure you'll find satisfying: It depends! It depends on what's causing the sciatica, and on which studies you believe.

Should I be concerned about my drinking?

DEAR DOCTOR K: During my daughter's wedding, and all the events surrounding it, I started drinking more than usual. But that was six months ago, and I haven't cut back to where I was before. When do I get concerned that I might have a drinking problem?

DEAR READER: It's not easy to answer your question. What constitutes "healthy" versus "harmful" drinking can vary quite a bit from person to person. So where is the line between social drinking and problem drinking? Does drinking every day or drinking a certain amount indicate a problem?

What is the Alexander Technique?

DEAR DOCTOR K: A friend mentioned something called the Alexander Technique, which is supposed to help relieve tension. Can you tell me more about it?

DEAR READER: I didn't know much about the Alexander Technique until I received your question. So I did some homework. I consulted with Dr. Eva Selhub, who is an internal medicine doctor and clinical associate at the Benson-Henry Institute for Mind Body Medicine.

What changes can I make to help reduce falls in my home?

DEAR DOCTOR K: I have osteoporosis, so my bones are going to break more easily. My doctor told me I should therefore try to avoid falls, but he didn't say how. Any ideas?

DEAR READER: A tumble can send a person with osteoporosis down the road to disability. Many factors can increase your risk for falls. Some have to do with your physical condition; others come from the environment. There is much you can do to reduce both types of risks.

What will happen during laboratory sleep testing?

DEAR DOCTOR K: My doctor thinks I may have sleep apnea, and he wants me to go to a sleep lab to be tested. What will happen during the testing?

DEAR READER: Sleep apnea is a serious health condition in which breathing stops or becomes shallower. In the most common form, obstructive sleep apnea, the tongue or throat tissues temporarily and repeatedly block the flow of air in and out of your lungs. This can happen hundreds of times each night. Laboratory sleep tests are the most reliable way to diagnose this problem.