Pneumonia caused by inhaling food, liquids or saliva is the most common cause of death in people with long-standing Parkinson's disease, an ailment whose many symptoms include difficulty swallowing.
The placement of a feeding tube reduces the risk of "aspiration pneumonia," but it neither prevents that complication nor appears to prolong life, according to published research and medical experts.
"What people who don't swallow well often die of is pneumonia -- either with or without a tube," said Kathleen M. Shannon, a neurologist and Parkinson's disease expert at Rush University Medical Center, in Chicago.
While pneumonia is the most common cause of death, it nevertheless occurs in only 20 percent to 30 percent of Parkinson's patients. Most of the rest succumb to the common illnesses of old age -- heart attack, stroke, cancer and bloodstream infections.
"My impression is that most people with Parkinson's die like people in the general population," said Carlos Singer, an expert in the disease at the Miller School of Medicine of the University of Miami.
Earlier this week, physicians caring for Pope John Paul II inserted a tube through his nose into his stomach so that he could receive sufficient water and nutrition. Those devices are generally kept in only a week or two, as they are uncomfortable and can cause nose and sinus infections. Patients needing them longer almost always have a larger tube inserted directly into the stomach through the abdominal wall in a simple procedure that can be done under local anesthesia.
The decision to place the nasogastric tube into the 84-year-old pontiff was an ominous sign suggesting that his Parkinson's disease, diagnosed in 1996, was causing life-threatening complications. On Feb. 24, after two hospitalizations for what were described as breathing problems following influenza, the pope underwent a tracheostomy. The procedure created a hole in his windpipe, through which he could breathe with less effort.
Reports from Rome last night said the pontiff had urosepsis, an infection of the bladder and the bloodstream. That, in turn, reportedly caused low and unstable blood pressure, a highly dangerous condition.
By itself, Parkinson's disease does not raise a person's risk of urinary tract infection. However, people immobile in the end stage of the disease sometimes have catheters placed in their bladders -- and those devices increase the chance of infection.
Parkinson's disease causes a slow depletion of several nerve-signaling chemicals called neurotransmitters. A lack of dopamine in the base of the brain, the brainstem, causes the tremors classically associated with the ailment. Loss of other neurotransmitters are responsible for the other two common complications, depression and dementia.
Parkinson's shortens life expectancy but not dramatically. In a group of patients in Minnesota between 1976 and 1995 who were followed by researchers at the Mayo Clinic, survival averaged 10 years, compared with 13 years in a similarly aged group of patients who did not have the disease. In a study from Sweden, a group of patients who had Parkinson's diagnosed in August 1989 was compared to a group of peers who did not have the disease. The average age at death was 82 for the former and 83 for the latter.
How Parkinson's shortens life is not entirely clear.
People suffering from the neurological ailment are less likely than people their age to have hypertension, diabetes and obesity, all of which raise the risk of the cardiovascular diseases that many Parkinson's patients ultimately die of. Some experts believe the inactivity that Parkinson's forces on most sufferers is their main risk factor.
"What it seems to mean is that if you don't have a normal activity level, your life is shorter," Shannon said.
Parkinson's disease disturbs the complicated coordination of muscles that occurs during swallowing and makes many patients less sensitive to foreign substances in their windpipes. Furthermore, their coughs are weaker and less able to clear the material.
A feeding tube helps prevent a person from gagging while eating or drinking. But it does not prevent bacteria-laden saliva and nasal secretions from getting into the lungs and causing infection. In one study, about 20 percent of elderly Parkinson's patients died of pneumonia. In another, the number was 27 percent.
In a 1997 study of nursing home residents with dementia (only some of whom had Parkinson's disease), those who had feeding tubes did not live longer on average than those without them.