Is Exposure to Antibiotics Linked to an Increased Risk of Parkinson's?

A 2019 study published in the scientific journal Movement Disorders suggests that heavy antibiotic use may be linked to the development of Parkinson's disease (PD).

The study reviewed past medical records and antibiotic purchase histories of people with PD and people without PD. Overall, the heavy use of certain antibiotics, such as broad-spectrum antibiotics, was found to be associated with an increased risk of developing PD. Other antibiotics including those against fungi and anaerobic bacteria (bacteria that don’t need oxygen to grow) were also found to be associated with an increased risk of PD. The timing of antibiotic use also seemed to play a role in PD development.

Why might antibiotic use and PD be linked?

Several recent theories on PD development have centered around the gut. Some experts suggest that gut bacteria play a role in PD risk. Taking antibiotics may impact normal gut bacteria (or gut flora). People with PD may have abnormal gut flora that can start years or even decades before PD diagnosis. Gut-related issues, like irritable bowel syndrome, constipation, or inflammatory bowel disease have also been associated with an increase in PD risk.¹

If gut bacteria play a role in the development of PD, and antibiotics impact gut bacteria, it makes sense that antibiotics may affect a person’s risk of getting PD. Of course, there are many potential genetic, environmental, and other factors that could play a role in PD. However, antibiotics may be a modifiable (changeable) risk factor if they are found to be associated with PD.

How was the study designed?

This recent study was based out of the University of Helsinki in Finland. It was a case-controlled study. This means that past records were used rather than enrolling people in real-time. This allows researchers to look at a variety of factors over many years. In this study, nearly 14,000 people who were diagnosed with PD between 1998 and 2014 were compared to over 40,000 without PD at the same time. Records were matched for age, place of residence, and sex to allow for direct comparisons.

Exposure to antibiotics was determined based on records of oral antibiotic purchase data. While this is not a perfect marker for the exact amount of antibiotic exposure a person might have had, it helps provide an estimate.

There were three different time periods studied in relation to antibiotic use. These were 1-5 years prior to the onset of PD, 5-10 years prior to onset, and 10-15 years prior.

What were the main findings?

The study found that significant or excessive usage to the following antibiotic drugs was associated with an increase in PD risk:

• Exposure to macrolides or lincosamides at any time. These antibiotics had the strongest connection to PD risk.
• Exposure to antibiotics against anaerobic bacteria or tetracyclines 10 to 15 years before symptom onset.
• Exposure to sulfonamides and trimethoprim or antifungal drugs 1 to 5 years before onset of symptoms.

These results suggest that heavy usage of certain classes of antibiotics may impact a person’s risk of developing PD. However, much more research is needed to strengthen these results and determine the exact relationship between antibiotics and PD, if there is one.^1,2

What does this mean for the future of PD?

Antibiotics are an important part of modern medicine. They can be life-saving in many instances or help prevent long-term damage.

More clinical trials and studies are needed to determine both the role the gut flora plays in PD development, as well as how antibiotic exposure might impact this. This current study also focused on heavy or excessive use of antibiotics in relation to PD and found an association. The benefits of using antibiotics occasionally for infections that require them may outweigh the risks, both known and unknown.

However, in addition to sparking more study into this potential relationship, the results of this study may have an impact on healthcare professionals and their prescribing practices. Learning that there may be a potential association with lots of antibiotics and PD may encourage a doctor to carefully consider antibiotic prescriptions. Not every short-term illness will need antibiotics and most infections will not need antibiotics for a very long period of time. Prescribing antibiotics only when needed and for the shortest (but still effective) time course may be encouraged as a result of this study.

What can I do now?

You can always discuss your antibiotic use or the need for antibiotics with your doctor. This includes asking why a certain drug is prescribed, what drug class it belongs to, what side effects it may have, and what, if any, other alternatives are available.