Parkinson’s disease (Parkinsonism) is marked by the presence of certain recognizable symptoms. These include uncontrollable shaking or tremor, lack of coordination, and speaking difficulties. However, symptoms vary and may worsen as the disease progresses.

The main symptoms of Parkinson’s include:

  • uncontrollable shaking and tremors
  • slowed movement (bradykinesia)
  • balance difficulties and eventual problems standing up
  • stiffness in limbs

Many doctors who diagnose this brain disorder rely on the Hoehn and Yahr rating scale to classify the severity of symptoms. The scale is broken into five stages based on disease progression. The five stages help doctors evaluate how far the disease has advanced.

Stage 1 is the mildest form of Parkinson’s. At this stage, there may be symptoms, but they’re not severe enough to interfere with daily tasks and overall lifestyle. In fact, the symptoms are so minimal at this stage that they’re often missed. But family and friends may notice changes in your posture, walk, or facial expressions.

A distinct symptom of stage 1 Parkinson’s is that tremors and other difficulties in movement are generally exclusive to one side of the body. Prescribed medications can work effectively to minimize and reduce symptoms at this stage.

Stage 2 is considered a moderate form of Parkinson’s, and the symptoms are much more noticeable than those experienced in stage 1. Stiffness, tremors, and trembling may be more noticeable, and changes in facial expressions can occur.

While muscle stiffness prolongs task completion, stage 2 does not impair balance. Difficulties walking may develop or increase, and the person’s posture may start to change.

People at this stage feel symptoms on both sides of the body (though one side may only be minimally affected) and sometimes experience speech difficulties.

The majority of people with stage 2 Parkinson’s can still live alone, though they may find that some tasks take longer to complete. The progression from stage 1 to stage 2 can take months or even years. And there is no way to predict individual progression.

Stage 3 is the middle stage in Parkinson’s, and it marks a major turning point in the progression of the disease. Many of the symptoms are the same as those in stage 2. However, you’re now more likely to experience loss of balance and decreased reflexes. Your movements become slower overall. This is why falls become more common in stage 3.

Parkinson’s significantly affects daily tasks at this stage, but people are still able to complete them. Medication combined with occupational therapy may help decrease symptoms.

Independence separates people with stage 3 Parkinson’s from those with stage 4. During stage 4, it’s possible to stand without assistance. However, movement may require a walker or other type of assistive device.

Many people are unable to live alone at this stage of Parkinson’s because of significant decreases in movement and reaction times. Living alone at stage 4 or later may make many daily tasks impossible, and it can be dangerous.

Stage 5 is the most advanced stage of Parkinson’s disease. Advanced stiffness in the legs can also cause freezing upon standing, making it impossible to stand or walk. People in this stage require wheelchairs, and they’re often unable to stand on their own without falling. Around-the-clock assistance is required to prevent falls.

Up to 50 percent of people at stages 4 and 5 experience confusion, hallucinations, and delusions. Hallucinations occur when you see things that aren’t there. Delusions happen when you believe things that aren’t true, even when you have been presented with evidence that your belief is wrong.

Dementia is also common, affecting between 50 and 80 percent of people with Parkinson’s, according to the Alzheimer’s Association. Side effects from medications at these later stages can often outweigh the benefits.

One complaint about the Hoehn and Yahr rating system is that it focuses solely on symptoms of movement. There are other types of symptoms associated with Parkinson’s disease, such as intellectual impairment.

Because of this, many doctors may also use the MDS-Unified Parkinson’s Disease Rating Scale. This rating system asks 50 comprehensive questions about both motor and nonmotor symptoms. It allows them to rate cognitive difficulties that may impair day-to-day tasks and the effectiveness of treatment.

This scale is much more complicated, but it’s also more thorough. It allows doctors to take into account a more complete picture that examines the person’s entire state of health instead of just motor symptoms.

Motor symptoms such as muscle stiffness and tremors are most commonly used to evaluate the progression of Parkinson’s disease. However, nonmotor symptoms are also common.

Some people will develop these symptoms years before developing Parkinson’s, and some will develop them after. Most people with Parkinson’s disease will also experience nonmotor symptoms.

Nonmotor symptoms include:

  • cognitive changes, such as difficulties with memory or planning, or slowing of thought
  • mood disorders such as anxiety and depression
  • sleep disorders such as insomnia
  • fatigue
  • constipation
  • vision problems
  • speech and swallowing problems
  • difficulties with sense of smell

Nonmotor symptoms may require additional treatment in many people. These symptoms can advance as the disease progresses.

Parkinson’s disease itself doesn’t cause death. However, symptoms related to Parkinson’s can be fatal. For example, injuries that occur because of a fall or problems associated with dementia can be fatal.

Some people with Parkinson’s experience difficulty swallowing. This can lead to aspiration pneumonia. This condition is caused when foods, or other foreign objects, are inhaled into the lungs.

As of 2021, there is no definite cure for Parkinson’s disease. There is also no definite known cause. It’s likely due to a combination of an individual’s susceptibility and environmental factors. Most cases of Parkinson’s disease happen without a genetic link.

According to research published in 2012, only 10 percent of people with Parkinson’s report having a family member with the disease. Many toxins are suspected and have been studied, but no single substance can be reliably linked to Parkinson’s.

However, research is ongoing. It’s estimated that twice as many men have the disease compared with women.

Ultimately, understanding both the motor and nonmotor symptoms of Parkinson’s can prompt earlier detection — and therefore earlier treatment, which can improve quality of life.

Knowing your personal risk factors can help you detect symptoms in the beginning stages. Keep in mind that not all people progress to the most severe stages of Parkinson’s. The disease can vary greatly among individuals.