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President Bush in the ICU: Why Does Pneumonia Strike Older Adults?
Former President George H. W. Bush and former First Lady Barbara Bush in Houston on March 29, 2015.
Credit: Tom Pennington/Getty Images

Former President George H.W. Bush was hospitalized on Jan. 14 following a bout of pneumonia, CNN reported today (Jan. 18).

In addition, Bush's wife, former first lady Barbara Bush, was admitted to the hospital today as a precaution because she was experiencing "fatigue and coughing," according to CNN.

The 41st president turned 92 last summer, and Barbara Bush is 91. Why does pneumonia often strike older adults? [27 Devastating Infectious Diseases]

One reason is that a person's immunity declines after age 50, "so it wouldn't be surprising if someone who's over 90 would have a reduced immunity," said Dr. Len Horovitz, a pulmonary specialist at Lenox Hill Hospital in New York City who has not treated either of the Bushes.

Pneumonia, which is characterized by inflammation of the lungs, is more common in the winter, Horovitz told Live Science. And, there are also many other respiratory illnesses, including the flu and common cold viruses, that are circulating at this time of year, he said.

Doctors "always hospitalize" elderly individuals if they get pneumonia, and hospitalization is particularly important if the person also has other medical problems, Horovitz said.

Although he isn't familiar with Bush's specific health conditions, Horovitz noted that the former president uses a wheelchair. This could mean that Bush also has neurological health problems, which could in turn mean that his cough may not be as effective at clearing mucus or secretions from the lungs as someone who is stronger, he said. (In fact, Bush does have a type of Parkinson's disease, according to CNN.)

Exactly what treatment is used for someone with pneumonia depends on whether that person's disease is caused by a virus or bacterium, Horovitz said. Viral pneumonia tends to be more contagious, but also typically causes a less severe infection than bacterial pneumonia, he said. Oftentimes, doctors will give a patient an antibiotic — even before test results come back to determine if the cause is viral or bacterial — "to cover, just in case it does turn out to bacterial," he said.

For older adults with pneumonia, doctors "have to be a little guarded" about giving a definitive prognosis, Horovitz said. "Pneumonia is not always straightforward, and in someone who's fragile with a compromised immune system because [he or she is] elderly, there's always a worry" that the individual may develop complications, he said.

Bacterial pneumonia, for example, can get into a person's bloodstream and spread through the body, Horovitz said. Complications can include kidney failure and abscess formation, he said. 

The disease can trigger a cascade of events that lead to "a multipronged assault" on the body, he said.

For older adults, however, vaccines are available that protect against certain types of bacterial pneumonia, he said. All adults over age 65 should get the vaccine, according to the Centers for Disease Control and Prevention.

Originally published on Live Science.