DEAR DR. DONOHUE: I am a 93-year-old woman with borderline diabetes and a minor heart problem. For the past six to 12 months, I have great difficulty remaining awake during the day. Every time I sit down to watch TV or to read, I fall asleep within minutes. My overnight sleep pattern remains good. Whether I sleep for five or 30 minutes, I awake confused and with no sense of the length of time that has passed. Can you help? Enclosed is a list of the medicines I take. – J.W.

ANSWER: Next to insomnia, daytime drowsiness follows as second on the list of sleep disorders. You say your pattern of sleep is good, but are you positive about that? Older people take longer to fall asleep. A greater proportion of the time they spend in bed is not sleep time. They have a large number of nighttime wakenings of which they’re often unaware. All of these factors make them drowsy during the day and force them to take involuntary naps.

If someone could observe you sleeping at night, he or she could confirm the nighttime sleep interruptions, or more serious conditions like sleep apnea — the condition where people stop breathing for 10 seconds at a stretch.

Of your medicines, meclizine is an antihistamine and could contribute to daytime sleepiness. So could atenolol, a beta blocker that sometimes affects people in this way. Discuss this with your doctor.

When you sit and feel sleep coming on, get up and walk about. Even better, take a short walk outside. A midmorning cup of coffee or tea might keep you awake.

You really have to see your doctor to be certain there aren’t any illnesses behind all this. A poorly functioning thyroid gland or anemia can make people chronically fatigue and make them prone to daytime napping.

DEAR DR. DONOHUE: My brother, 76, went into the hospital to correct a stomach problem. One day after surgery, he did not wake up, and the doctor said he was septic. What causes this? What can be done for it? Is it always fatal? – R.M.

ANSWER: Sepsis indicates bacteria or bacterial byproducts have entered the blood and are causing great disturbances. Temperature rises; the heart speeds up; breathing becomes rapid. If the blood invasion is great, blood pressure drops, and organs like the kidneys and liver fail. This is septic shock – an often-fatal illness, especially in older people.

Medicines to raise blood pressure, oxygen to combat the oxygen drop in the blood, fluids to support circulation, antibiotics for infection and often the use of a ventilator can sometimes reverse the process.

The causes are many. Even relatively innocent infections can enter the blood. Surgery is always a potential cause, since cutting the skin exposes the body to bacterial invasion. Sepsis happens to 750,000 patients yearly in the United States.

DEAR DR. DONOHUE: My wife is 79 and has dementia. She had a blood clot in her foot, and they installed a filter to prevent the clot from going up to her lungs. Her leg has been swollen for a month, and the doctors say it could stay that way for some time. Can you give any information on this? – R.J.

ANSWER: I have to reconstruct the story. If I make an error in doing so, I apologize.

Your wife had a clot in a vein in her foot or leg, most likely the leg. That’s thrombophlebitis. To prevent pieces of the clot from breaking loose and traveling to the lung, the doctors put a filter in the vein that carries blood back to the heart. The filter traps any clot fragments in the blood.

A swollen leg after a clot is common. If you can help your wife elevate her leg many times during the day, it will help the swelling go down. Even when she sits, the involved leg should be elevated as high as she can tolerate. An elastic stocking might help, if her doctor agrees to it.

There’s no magic process that hastens the return to normal leg size.

DEAR DR. DONOHUE: How many times should a person be vaccinated for pneumonia? One source says every seven to 10 years; another, just one time. What’s the best way to go? – G.K.

ANSWER: The “pneumonia” vaccine is misnamed. It’s a vaccine for only one kind of pneumonia, pneumococcal (NEW-moe-KOK-ul) pneumonia. That’s the most common kind of bacterial pneumonia, and it’s quite dangerous for older people.

The Advisory Committee on Immunization Practices, a panel of vaccine experts, recommends that only one shot of the vaccine be given to those age 65 and older. If the vaccine was given to a person younger than 65 and if five years have elapsed since the vaccine was given, a second shot is recommended.

Another group of experts, the United States Preventive Services Task Force, recommends that everyone who had the vaccine be revaccinated at age 75.

More doctors follow the first set of recommendations.

Dr. Donohue regrets that he is unable to answer individual letters, but he will incorporate them in his column whenever possible. Readers may write him or request an order form of available health newsletters at P.O. Box 536475, Orlando, FL 32853-6475. Readers may also order health newsletters from www.rbmamall.com