Former President George H.W. Bush, who has been placed in intensive care at a Houston hospital, is suffering from pneumonia and has vascular parkinsonism, a rare syndrome that mimics Parkinson's disease. The 92-year-old Bush also broke a vertebra in 2015 and has used a motorized scooter or a wheelchair in recent years. Some answers to common questions about his health:
Q: WHAT ARE THE RISKS OF PNEUMONIA?
A: Pneumonia is an infection of the lungs that can be mild or severe. Elderly patients are at risk of deadly complications.
The former president wrote to President-elect Donald Trump on Jan. 10, saying that he would be unable to attend Friday's inauguration because of doctor's orders: "My doctor says if I sit outside in January, it will likely put me six feet under. Same for Barbara. So I guess we're stuck in Texas."
Q: WHAT IS VASCULAR PARKINSONISM?
A: People diagnosed with the condition walk with shuffling steps, and brain scans suggest they have suffered small strokes. However, they do not have the characteristic tremors of Parkinson's disease, and they do not respond to drugs for Parkinson's.
"They look like Parkinson's from the waist down. From the waist up, they look very expressive," said Dr. Alberto Espay of the University of Cincinnati's Gardner Neuroscience Institute.
Q: IS IT DIFFERENT FROM PARKINSON'S DISEASE?
A: Yes. It does not get steadily worse in the same way Parkinson's does. Classic Parkinson's disease develops when cells that produce one of the brain's chemical messengers, called dopamine, begin to deteriorate and die. Dopamine transports signals to parts of the brain that control movement. Parkinson's symptoms appear after enough dopamine-producing cells die that there's too little of this neurotransmitter in the brain.
Vascular parkinsonism can closely mimic a number of other disorders, including classic Parkinson's, progressive supranuclear palsy and excessive fluid on the brain.
Q: WHAT HAS PRESIDENT BUSH SAID ABOUT THE CONDITION?
A: In a 2012 interview with Parade magazine, Bush said: "It just affects the legs. It's not painful. You tell your legs to move, and they don't move. It's strange, but if you have to have some bad-sounding disease, this is a good one to get."
Bush said the symptoms have been difficult for him, "because I love being active, (playing) sports, being in the game. . But you just face the reality and make the best of it."
Q: WHO GETS IT?
A: People in their 70s and older are most likely be diagnosed, said Dr. Tanya Simuni who conducts research on Parkinson's and other movement disorders at Northwestern Medicine in Chicago. She calls it a "difficult diagnosis" because of the lack of accurate diagnostic tests.
The risk factors are the same as for stroke and heart disease: history of smoking, lack of exercise and poor diet. It's rarer than Parkinson's disease, which affects about 1 million Americans. In contrast, roughly 20,000 people have been told they have vascular parkinsonism.
Q: HOW IS IT TREATED?
A: Since the condition does not respond well to drugs used to treat Parkinson's disease, treatment relies on lowering the risk factors for stroke. That means quitting smoking, exercising, eating a healthy diet and perhaps taking a daily aspirin. Preventing falls is important, so a patient may receive physical therapy to improve balance.
Q: WHAT CAUSES THE DISEASE?
A: This is where answers get tricky. Conventional thinking says the disease is caused by strokes. But without a perfect test, lots of problems get lumped under the umbrella. Espay has written a paper questioning whether most parkinsonism is related to vascular disease. He's also debated the topic at a recent neurology conference.
Q: IS THERE A CURE?
A: Physical therapy can help with balance and walking, but the damage cannot be reversed, said Dr. Corneliu Luca, assistant professor of neurology at University of Miami. "If you do not control risk factors for stroke, they can have another stroke, and the walking can get even worse," Luca said.
Q: WHAT COMPLICATIONS ARE MOST WORRISOME?
A: Falls are the biggest concern because they can lead to fractures, Simuni said. Bush took a spill in 2015 and fractured his C2 vertebra, the second one below the skull. It's not known whether that fall was directly related to parkinsonism.
Follow AP Medical Writer Carla K. Johnson on Twitter at https://twitter.com/CarlaKJohnson .