Q. I'm recovering from a bad case of a painful shingles infection. I'm told that the viral infection took hold because of a low level of immunity. But just one month before I came down with shingles, I had a very thorough annual physical examination including all sorts of blood tests which were normal. My doctor pronounced me in excellent health for my age (79). I'm puzzled. How can I be in such good health and also have a low level of immunity to infection? A. You probably are in good health, but you may be overestimating the value of an annual physical examination.

Your immunity tends to decrease as you reach older age, so coming down with shingles at 79 isn't necessarily a sign of poor health. It's more likely a natural consequence of aging and the nature of shingles infection, a flare-up of a dormant varicella-zoster (chicken pox) virus infection.

Many people believe that a doctor's examination is capable of discovering any hidden disease that may be lurking. Not so. In fact, taking your history -- listening to your current and past medical problems -- is much more helpful to your doctor in sizing up your general state of health.

Once regarded as an important part of good medical care, the annual physical examination has undergone some rethinking. Now, experts recommend selective examinations based on a person's age and sex.

Rather than needlessly repeating normal laboratory tests or examining parts of the body that a person doesn't have any complaints about, many doctors instead focus their attention on aspects of the history and physical that are likely to turn up serious conditions when they can be treated early. As an example, the American Cancer Society recommends that people over 40 have annual stool examinations for trace amounts of blood, a sign of possible polyps or cancer of the intestines.

So far there are no guidelines that all doctors agree on for routine health exams, but I think it's important for physicians to adopt some standard procedure to evaluate the health of their individual patients. Q. My 6-month-old son still does not sleep through the night. He typically wakes up once, twice and sometimes three times at night. When he cries I try just patting him back to sleep. Is this encouraging his crying? How can I get him to sleep through the night? A. Your baby is probably acting normally when he wakes up during the night, but you also may be encouraging his nighttime waking.

The average 2-week-old sleeps about 16 hours a day, with the longest sleep period about 4 1/2 hours. By 3 to 4 months of age, total sleep is about 15 hours, and longest sleep time is about 7 1/2 hours. Between 6 and 8 months, most infants sleep through the night, supplemented by two daytime naps. But between 9 and 12 months, up to half of all infants resume occasional night waking. This decreases to about one in five infants who continue to have regular night waking between 1 and 2 years of age.

Some babies sleep for shorter periods and more lightly than others. Infants also have two different types of sleep -- quiet and active. In the active stage, which occurs about once an hour during sleep, the infant seems to wake up, move about, moan or make noise. Some new parents may mistake this stage of sleep for waking up, so be careful not to respond too soon to your baby's stirrings.

If your baby wakes up and doesn't seem to be hungry or in distress, try letting him lie awake even if he gets fussy and cries. Otherwise you run the risk of making his behavior a nighttime habit.

Other things you can try: Don't let your baby sleep most of the day. Put your baby to sleep later in the evening. Feed your baby before putting him down for the night. Make sure your baby's not too hot or too cold. For example, he might be waking up after kicking his covers off in a cool room. Avoid stimulating activities close to bedtime.

Although many parents believe it works, studies don't show that feeding solid foods to infants makes them sleep better through the night.