Parkinson's disease is progressive: It gets worse over time. The primary Parkinson's disease symptoms — tremors, rigid muscles, slow movement (bradykinesia), and difficulty balancing — may be mild at first but will gradually become more intense and debilitating.

Stages of Symptoms in Parkinson's Disease

Parkinson's symptoms can become more severe over a period of 20 years or even longer. How fast the symptoms intensify varies from person to person.

To find out how far the disease has progressed, many doctors use a rating scale called the Hoehn and Yahr Staging of Parkinson's Disease:

Stage one Mild symptoms affect only one side of the body. Stage two Symptoms affect both sides of the body, with posture and gait changes. Stage three Body movements are slow, and balance is impaired. Stage four Symptoms are severe and disabling, muscles become rigid, the patient can't live alone, and walking is limited. Stage five Wheelchair-bound or bedridden, the patient needs constant care.

While your doctor may be able to tell you how far along you or a loved one is on this scale, how soon you'll get to the next stage is not predictable. You can expect that as you notice your symptoms worsening, your physical functioning will also start to decline.

Parkinson’s Disease Symptoms of Dementia

Up to one-third of people living with Parkinson's disease experience dementia, according to the Parkinson's Disease Foundation. Problems with dementia may include trouble with memory, attention span, and what is called executive function — the process of making decisions, organizing, managing time, and setting priorities.

RELATED: 12 Famous People With Parkinson's Disease

How Treatment Helps

Medical treatment to help restore the essential neurotransmitter dopamine, and at-home remedies like exercise, can help ease your symptoms. Although Parkinson's disease has no cure, you can find out if you or a loved one is right for one of hundreds of clinical trials for Parkinson's disease at the Fox Trial Finder.

Tracking your response to treatment helps determine how advanced your condition is. The stages of Parkinson's treatment generally progress in the following order:

No medication needed In its early stages, Parkinson's disease symptoms may be very mild and may not need to be treated. Good response to medication As symptoms begin affecting your functioning, the Parkinson's medication Sinemet (a combination of carbidopa and levodopa) can help. It is able to significantly and effectively reduce symptoms for 5 to 10 years in many patients, and longer in about 25 percent of patients. But it comes with side effects like tics and involuntary movements (called dyskinesias). Other Parkinson's medications, called dopamine agonists, include Mirapex (pramipexole), Cycloset or Parlodel (bromocriptine), and Requip (ropinirole). Waning medication response When the effectiveness of a medication begins to wear off, you'll need to increase the amount you're taking or add another to boost the carbidopa-levodopa combo. Examples include MAO-inhibitors, such as selegiline and rasagiline, and COMT-inhibitors entacapone and tolcapone; these help therapy last longer. Unpredictable medication response Instead of occurring at predictable intervals, breakthrough symptoms may start to show up at random and may be triggered by stress and anxiety. At this point, medications will be continuously monitored. Dyskinesias These involuntary movements occur when your medication dose has reached its peak performance. Adjusting your medication dose — and perhaps surgery — may help. Severely unpredictable symptoms In the most advanced stages, severe symptom flare-ups alternate with severe dyskinesias, despite medication adjustments. At this point, surgery is a treatment option. Called deep brain stimulation, this surgery implants electrodes in the brain that are connected to an external device, somewhat like a heart pacemaker, to help control electrical impulses affecting movement and flexibility.

Parkinson's Disease Symptoms: Life Expectancy

Even though Parkinson's disease is a serious, progressive condition, it is not considered a fatal illness. People who have Parkinson's disease usually have the same average life expectancy as people without the disease.

But when the disease is in its advanced stages, Parkinson's symptoms can lead to life-threatening complications, including:

Falls that lead to fractured bones

Pneumonia

Choking

Thinking about the progression of Parkinson's disease can be frightening. But proper treatments can help you live a full, productive life for years to come. And researchers hope to one day find ways to halt the progression of Parkinson's and restore lost functioning.