Dear Doctor: I understand that Alzheimer's disease causes memory loss and leads to dementia. But when someone has Alzheimer's, what is the actual cause of death?

Dear Reader: Alzheimer's disease is a progressive disease of the brain in which dementia is the most noticeable of numerous symptoms. Changes within the tissues of the brain slowly destroy vital connections between different regions of the brain, and between the brain and the body. The result is that Alzheimer's disease is the fifth-leading cause of death among adults over 65, and is the sixth-leading cause of death for all adults nationwide.

The disease was first identified in 1906 by Dr. Alois Alzheimer, who connected a patient's dementia to certain physical abnormalities he found when he examined her brain after her death. But the human brain is so intricate and Alzheimer's itself is so complex that more than a century later, scientists are still working to discover both the cause of, and a cure for, the disease.

Although each case of Alzheimer's is different, researchers have identified three general stages of the disease. In the first stage, symptoms of cognitive impairment, such as memory loss or confusion, have either not yet appeared or are quite mild. However, significant changes are taking place within the brain, including nerve death, tissue loss and the buildup of abnormal clumps and tangles of protein.

These changes lead to the second stage of the disease, during which symptoms become more pronounced. Patients begin to experience significant memory loss, confusion, impaired reasoning, poor spatial skills and a loss of language. By the final stage of Alzheimer's, the brain has shrunk dramatically. Patients can no longer communicate, are unable to recognize faces, even of family members and loved ones, and are unable to care for themselves.

Patients with advanced-stage Alzheimer's need 24-hour supervision and help with personal hygiene, dressing and eating. Changes in brain function make it increasingly difficult for them to move about, sit up and even swallow. This leads to complications such as bedsores, skin infections, blood clots and sepsis. Injuries from falls are common. Difficulty in swallowing makes eating and drinking an ongoing challenge, and can lead to weight loss, malnutrition and dehydration.

The most common cause of death among Alzheimer's patients is aspiration pneumonia. This happens when, due to difficulty in swallowing caused by the disease, an individual inadvertently inhales food particles, liquid or even gastric fluids. Because our mouths and throats contain numerous bacteria, these are carried deep into the lungs. There they multiply and grow, which leads to pneumonia. Due to the impaired immune systems of Alzheimer's patients, pneumonia is often fatal.

It's important to remember that Alzheimer's patients are often elderly and thus may have a range of medical conditions associated with advancing age. These include stroke, cancer, heart disease, diabetes, hypertension and stroke, any of which can cause death, whether or not Alzheimer's is present.

(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. Owing to the volume of mail, personal replies cannot be provided.)

Dear Doctor: Sometimes when I awake from a good sleep, one of my hands is asleep, and I have to shake or massage it back to normalcy. It's usually my thumb and the two fingers next to it. Is this normal?

Dear Reader: No, this is not normal. Your symptoms are typical of carpal tunnel syndrome, which occurs because of a compression of the median nerve at the wrist. The median nerve provides sensation to the thumb, index and middle fingers. It also supplies the muscles that control the thumb and the smaller muscles that control the index and middle fingers.

The median nerve is in real cramped quarters as it makes its way through the wrist. As you look at the palm surface of your hand and move your eyes toward your wrist you can see multiple tendons. The median nerve has to share room with nine of these tendons that are within the carpal tunnel. When there is inflammation in the wrist, or the tendons become inflamed, the median nerve gets compressed.

The first symptoms are often noted during sleep, when we have a tendency to flex the wrists, so that our hands curl. This flexion of the wrists causes greater compression of the median nerve, which leads to the sensation of tingling in the thumb and the index and middle fingers, as if your hands are falling asleep.

Carpal tunnel syndrome is very common and can be caused by repetitive work involving recurrent compression on the median nerve. Studies have been mixed as to the type of work that can cause this. One study showed that recurrent use of a computer mouse was associated with carpal tunnel syndrome, but there has been no consistent association with recurrent keyboard use.

Women are more likely to have carpal tunnel syndrome than are men. The rate is 5 percent in the general population, but women have rates ranging from 7 percent to 18 percent. One study, published in Environmental Research, for example, found a greater rate of carpal tunnel syndrome in female butchers and meat cutters.

Diabetes, rheumatoid arthritis and hypothyroidism are diseases that are associated with an increased risk of carpal tunnel syndrome.

As for a diagnosis, that can be done through a physical exam or through a nerve conduction study.

For starters, I would consult your doctor. If he or she diagnoses carpal tunnel syndrome, wearing a wrist brace at night would be the likely recommendation. Whether rigid or of a softer variety, wrist braces help because they don't allow the wrist to curl when you're sleeping. In addition, a physical therapist can teach stretches and range of motion exercises that can ease symptoms.

Finally, pay attention to signs of weakness in the hand. This would be noticed mostly in the use of the thumb, such as if you start dropping keys or begin having difficulty holding a cup. These signs suggest additional treatment, such as surgery, may be needed.

(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. Owing to the volume of mail, personal replies cannot be provided.)

Dear Doctor: Sometimes I get a sudden hissing sound in my right ear that lasts for a few minutes and then slowly goes away. What is it, and is there anything I can do to make it stop?

Dear Reader: What you're experiencing is known as tinnitus, which is the medical term for a perceived sound that doesn't have an external source. Tinnitus is not a condition in and of itself, but is instead a symptom of some other underlying problem.

Exposure to noise is a major cause of tinnitus, as is hearing loss. Both can result in damage to the sensitive hair cells that line the cochlea. This is the portion of the inner ear that translates vibrations into nerve impulses, which are then sent to the brain to be interpreted as sound.

Blockage due to earwax buildup, as well as changes to the ear bones as we age, can contribute to tinnitus. Some medications, including certain antibiotics, cancer drugs, antidepressants and high doses of aspirin, are known to play a role in tinnitus.

Although the most common form of tinnitus involves a ringing in the ears, people with this condition may also hear the hissing you describe, as well as buzzing, clicking, humming, whistling or a roaring sound, like wind. In rare cases, patients with tinnitus have even reported hearing music.

Tinnitus can affect one or both ears. It ranges in volume from a low, background noise that is bearable and even forgettable, to sounds so loud and persistent that they interfere with daily life. In many cases, tinnitus is temporary. In severe cases, the phantom sounds never go away.

It is estimated that up to 45 million Americans -- that's 15 percent of the population -- report having some form of tinnitus on a regular basis. Like you, the vast majority of them have subjective tinnitus, which is sound that only the patient can hear. In objective tinnitus, which affects just 1 percent of the population, the sounds a patient hears are audible to others as well. The causes of objective tinnitus are most often internal conditions related to blood flow in vessels near the ear.

Men are more prone to tinnitus than women, and it becomes increasingly common as we age. Individuals who work in loud environments, such as factories and construction sites, are at increased risk. Recent studies suggest that earbuds, which sit so close to the delicate structures of the inner ear, may also put users at higher risk.

At this time, there is no single treatment for tinnitus. An examination by an ear specialist, known as an otolaryngologist, can pinpoint whether tinnitus is due to earwax buildup, medication or, more rarely, a blood vessel condition. These are often treatable. If not, your doctor can help you explore noise suppression techniques such as using a white noise machine, or masking devices that are worn in the ears.

Meanwhile, you can take steps to lessen the impact of tinnitus. Make sure your blood pressure is under control, avoid loud noises, which can set off a tinnitus episode, and -- this will improve your overall quality of life -- be sure to get enough rest.

(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. Owing to the volume of mail, personal replies cannot be provided.)