The autonomic nervous system (ANS) is the part of the peripheral nervous system (PNS) that controls involuntary or unconscious actions within the body.

The autonomic nervous system regulates the function of many organs and so controls the following:

• heart rate
• breathing
• body temperature
• blood pressure
• digestion
• sexual function.

When the ANS fails to work properly it is called autonomic dysfunction.

Autonomic dysfunction often occurs in Parkinson’s due to the loss of dopamine-producing cells and the presence of microscopic protein deposits called Lewy bodies in the brain. As a result, a number of non-motor symptoms may be experienced. Research suggests that the peripheral nervous system may be affected long before such symptoms appear.

If autonomic dysfunction is severe, atypical parkinsonism, such as multiple system atrophy (MSA), should be suspected.

Please click on the links below for information on individual symptoms related to ANS dysfunction:

• bladder problems including urgency, frequency, incontinence and night time urination
• constipation and weight loss
• drooling (sialorrhoea)
• dry eyes
• excessive sweating
• increased sensitivity to heat and cold and an inability to regulate body temperature (see Skin & sweating)
• loss of sense of smell
• loss of sense of taste
• low blood pressure (orthostatic or postural hypotension) and fainting or falls related to this
• pain, often related to being ‘off’
• sexual dysfunction 
• swallowing difficulties (dysphagia).

Scientists now recognise that many medications used to treat Parkinson’s can affect the ANS and so make symptoms worse. It is important to monitor your medications and symptoms so that you can discuss these with your doctor. He or she may then be able to adjust medications to reduce the impact on the ANS and so improve symptom control. See Keeping a diary for more information on this and how it can help.

Research suggests that about 90% of people with Parkinson’s experience autonomic dysfunction which may considerably reduce quality of life.

Content last reviewed: January 2020

We would like to thank Prof Jorik Nonnekes (Radboud University Nijmegen Medical Centre, The Netherlands) for his help in reviewing this information.