Dear Doctor: My husband thinks that sleeping for more than five hours a night is a waste of time. But I just read that not getting enough sleep can predispose people to illness. Is this correct? I would love to be able to persuade him that sleep is actually good for you.

Dear Reader: Getting enough hours of sleep is crucial to staying healthy. Yet a surprising number of people resist the idea. We will happily tell you what is known about the benefits of sleep and hope that it will be enough to persuade your husband.

People who don't get enough sleep simply don't function as well as those who do. Paying attention at work, staying alert while driving, performing tasks that require decision-making or a judgment call -- all become more difficult when you haven't had enough sleep. Sadly, chronic sleep insufficiency can cause behaviors that lead to injury and death.

Hundreds of studies over the years have shown that a lack of sleep, which is often referred to as "sleep insufficiency," also plays a role in chronic disease. Researchers have concluded that lack of sleep adversely affects the immune system and increases inflammation. Individuals who don't get enough sleep on a regular basis are at increased risk of cardiovascular disease, diabetes, cancer, hypertension and obesity.

How much sleep is enough?

Adults need at least seven hours of sleep per night. For adolescents, that number climbs to nine hours per night. Getting adequate sleep helps regulate the metabolism, keeps emotions on an even keel, aids in reasoning and memory, helps the brain recuperate and plays a role in physical coordination. In fact, sleep is so important to health and well-being that the Centers for Disease Control and Prevention consider the chronic shortage of sleep among Americans to be a public health issue.

Children who don't get enough sleep are more likely to become obese than those who sleep enough. Both children and adults who don't get enough sleep are at increased risk of mental and emotional problems as well. Depression, anxiety, impaired behavior and mood disorders are all associated with lack of sleep.

The latest scientific data to bolster the importance of getting enough sleep comes from a fascinating study published last February. Conducted at the University of Washington Medicine Sleep Center in Seattle, scientists studied 11 sets of identical twins. Although the twins shared identical DNA, their natural sleep patterns differed greatly.

Each of the study participants slept at least seven hours per night. But one twin in each pair slept at least one hour less per night than the other twin. When blood samples collected from each participant were examined, the twin who got less sleep had measurably lower function in the immune system than did the twin who slept more. And, as you noted in your question, this means less sleep can lead to greater susceptibility to illness.

The truth is, we get quite a few questions about sleep, battling insomnia and how to sleep better. We'll address these soon in an upcoming column.

(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: I am 60-year-old female who suffers from darkening of my face. A doctor did a biopsy and it was determined that I suffer from melasma, which began as soon as I hit menopause. Dermatologists seem unable to help. What can I do?

Dear Reader: Melasma is the hyperpigmentation of the skin that occurs mostly upon the sun-exposed areas of the face. This manifests as darker patches of skin that can be irregular and, when severe, cause significant cosmetic disfigurement, which can have a significant impact upon one's social life and the ability to enjoy leisure activities.

It has been linked primarily to various alterations in female hormones. In fact, 90 percent of cases occur in women. Potential melasma-inducing changes occur in the third trimester of pregnancy, when estrogen and progesterone levels are higher, and among women who take oral contraceptives. The breast cancer drug tamoxifen, which blocks estrogen receptors, also has been linked to the condition, and -- for melasma of the arms -- so has hormone replacement therapy. Menopause may increase the chance of getting melasma in other areas beside the face.

Because the condition occurs upon sun-exposed areas, the first intervention you can do is to use sunscreen with an SPF of at least 30. Your dermatologist may already have recommended skin-lightening agents such as hydroquinone, azelaic acid, mequinol or kojic acid. The side effects of those substances include redness and irritation of the skin, even peeling. Worst of all, bleaching agents can cause a decrease in pigmentation, so in addition, you may have to deal with patches of non-pigmented skin.

Retinoids (such as tretinoin), which are derivatives of vitamin A, also work well to treat melasma and have been used in combination with bleaching agents. The best efficacy was seen in a study showing that a combination of hydroquinone, tretinoin and a steroid cream led to a 75 percent reduction of pigment in 70 percent of patients.

Superficial skin peels using chemicals -- often glycolic acid or salicylic acid -- have also shown success against melasma. One study compared the results of 20 patients in India who used six glycolic acid peels to the results of 20 patients who used a combination cream of hydroquinone, tretinoin and hydrocortisone. Eighty percent of the peel group reported their improvement as excellent, versus 60 percent of the cream group. However, other studies have found that chemical peels were no different than bleaching creams in regards to efficacy.

Laser therapy has been used for melasma, but it has significant side effects and may lead to both decreased and increased pigmentation. The side effects are greater in those with darker skin. Finally, two studies have found that the topical serum rucinol, which inhibits the formation of melanin, can decrease pigmentation.

In your case, I would first and foremost try to decrease the sun exposure to your face and, if you're taking hormone replacement therapy, I would talk to your doctor about stopping it. Next, consider the use of a cream that combines hydroquinone, tretinoin and a steroid. If that doesn't work, consider chemical peels. If those don't work, then topical rucinol would be an option.

One other course of action is to use makeup with titanium or zinc oxide. Not only do these minerals camouflage the pigmented areas, they also work well as sunscreens.

Some of my patients have dealt with melasma, and I know it can be frustrating, but keep in mind that the dark spots may be more obvious to you than to others.

(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: Our youngest daughter is starting college in New York City this fall, and on top of all the empty nest emotions my husband and I are dealing with, a friend has warned us about something she saw on the news called "rat urine disease." What is it? Should we be worried?

Dear Reader: There's nothing like a rare and off-putting health threat to get the 24-hour news cycle into a lather. We'll spare you additional worry and jump right to the point: No, you do not need to add rat urine disease to the list of challenges we all face when a child first leaves home.

That said, the reason that leptospirosis -- that's what it's called -- has created headlines is that three individuals in the Bronx contracted the disease last winter. One of them later died. But according to health officials in New York, leptospirosis is extremely rare. In a city of 8.5 million residents, between one and three cases of the disease are seen each year. Add in the fact that the disease is treatable with antibiotics, and the threat level plummets.

Now that you're (hopefully) breathing easier, let's talk specifics.

Leptospirosis is the name of the disease caused when leptospira, a corkscrew-shaped bacterium, enters the body. It produces a wide range of symptoms, many of which can be mistaken for other diseases. These include high fever, chills, nausea, diarrhea, rash, headache, jaundice and muscle aches. In some cases, infected individuals may not have any symptoms at all. Untreated, leptospirosis may lead to liver or kidney failure, or meningitis. Treatment is with antibiotics, with early diagnosis yielding the best outcomes.

Although the news reports your friend saw focused on rats, which are the most common carriers of leptospira in urban environments, the bacterium can be found in a range of animals. These include cattle, pigs, dogs and horses, other rodents, and some wild animals.

Infected animals, which don't show any disease symptoms, will continue to excrete the bacteria for several months or even several years. Humans become infected when they come into contact with either the urine of an infected animal, or its bodily fluids, other than saliva. You can also pick up the infection from a substance that carries the infected urine or fluids, such as soil, water or trash.

The bacterium typically enters the body through the skin, particularly if it is broken due to a scratch or a cut. It can also enter through the mucous membranes of the mouth, eyes or nose. According to the Centers for Disease Control and Prevention, wide outbreaks of leptospirosis are usually caused by exposure to contaminated water, such as floodwaters. Person to person transmission is rare.

If you're still worried, recommend the following precautions to your daughter:

-- Steer clear of rats and their habitats.

-- If you do make contact, wash the affected body part thoroughly with soap and water.

-- To clean areas where rats may have been, use one part household bleach and 10 parts water, which kills the leptospirosis bacteria. Wear gloves and goggles.

-- If you develop symptoms after making contact with suspected rat urine, whether directly or in a rat-infested environment, seek medical care.

(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.)