Former U.S. Attorney General Janet Reno has died at age 78 from complications of Parkinson's disease, her family announced today. But how do people die from this disease?

In patients with Parkinson's disease, the brain cells that produce a chemical called dopamine start to die off. It's not clear what triggers the death of these cells, but researchers do know that dopamine is important for the control of muscle movement. Parkinson's patients experience symptoms such as tremors, slowed movements, muscle stiffness and impaired balance.

Parkinson's itself is usually not considered a deadly disease, and many people with the disease have a life expectancy that's close to the average life expectancy in the general population, according to the Parkinson's Disease Foundation.

"You die with Parkinson's disease, not from it," according to the Michael J. Fox Foundation for Parkinson's Research. Reno's family did not release any further details about her death.

But in some cases, advanced symptoms of Parkinson's disease can lead to complications that result in death, the Michael J. Fox Foundation says. For example, patients can have problems swallowing because they have a loss of control over the muscles in their throat. [3 Myths About Parkinson's Disease]

Swallowing problems can cause patients to inhale small bits of food, which may result in aspiration pneumonia, an infection of the lungs that can be life-threatening. A 1999 study of people with Parkinson's disease that followed patients for 10 years found that pneumonia was the most common cause of death in these patients, causing nearly one-third of all deaths among patients in the study.

Patients also may have impaired balance, which can result in falls that lead to serious or even fatal injuries, the Michael J. Fox Foundation says.

A 2010 study of more than 200 people with Parkinson's disease in Norway found that, on average, patients were diagnosed with the disease at age 65, and lived for 16 years after their diagnosis, to age 81, according to the Parkinson's Disease Foundation. Those who lived with the condition for a shorter time than the average tended to be male, have more severe problems with their movements (in particular, problems with balance and walking) or have symptoms of dementia along with their Parkinson's.

Reno, who was the first female attorney general in the United States, was diagnosed with Parkinson's in 1995 (at age 57), while she was still in office, and she held the position until 2001. She died at her home in Miami-Dade County, Florida, according to The New York Times.

Original article on Live Science.

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