Painkillers may reduce the risk of Parkinson's, reported five newspapers (6 November 2007). The newspapers briefly, but generally accurately, reported the results of a case-control study. The study does have some weaknesses, and case control studies rarely provide definitive evidence for cause and effect. The call for further research seems appropriate.
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On 6th November 2007, five newspapers (1-5) reported that painkillers such as ibuprofen reduce the risk of Parkinson's.
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The research, published in Neurology (6), was a case-control study involving 579 people (293 with Parkinson's; 286 controls). The risk of developing Parkinson's disease was significantly reduced in patients who had regularly taken non-steroidal anti-inflammatory drugs (NSAIDs), when 2 to 14 pills were taken per week, and when NSAIDs were taken for over 24 months. When analysed by gender, the reduction in risk was significant in women, but not in men. There was no significant reduction in risk if NSAIDs had been taken five years or more prior to diagnosis. Non-significant reductions in the risk of developing Parkinson's were seen with aspirin usage. The reported risk reductions were based on small numbers of participants.
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The newspapers briefly, but generally accurately, reported the results of the study. One (5) reported that drugs that such as paracetamol have no effect; these were not evaluated in the study. None of the newspapers reported that the reduction in risk in women with aspirin was not statistically significant. The study does have some weaknesses; case-control studies can be subject to a number of biases and seldom provide definitive evidence for cause and effect. Therefore, the recommendation for further research seems appropriate.
Evaluation of the evidence base for the protective effect of NSAIDs against Parkinson's disease
Where does the evidence come from?
The research was conducted by researchers from the University of California, Los Angeles, USA, led by Dr A. Wahner. Funding was provided by the National Institute of Environmental Health Sciences, the Southern California Environmental Health Sciences Center, and The American Parkinson's Disease Association.
What were the authors' objectives?
To investigate the potential for a protective role for NSAIDs in Parkinson's disease.
What was the nature of the evidence?
The study was a case-control study of 579 people; 293 had developed idiopathic Parkinson's disease within the previous three years, and 286 were controls. To be included, cases had to have lived in California for at least 5 years, have no diagnosed neurological or psychiatric disorder, were not in the terminal stages of illness, and had clinically probable or possible Parkinson's disease which was confirmed using set criteria reported in the paper. Controls were randomly selected from rural Californian counties and were matched to cases in terms of age, race and gender. Telephone interviews were conducted and questionnaires completed by the participants. The control group had a greater proportion of black (3.2%) and Asian (3.9%) people, and fewer Latino people (7.7%) than the Parkinson's disease group (1%, 1.4%, and 10.9% respectively). In addition, the control group had a greater number of people that had remained in education beyond 12 years (68% vs. 55%) and people who had smoked more heavily or for a more prolonged period of time (35% vs. 27%).
How did participants differ on their levels of exposure to the factor of interest?
Participants were categorised either as regular users (at least two pill per week for at least one month) or non-regular users (either less than two pills a week, less than one month treatment, or not taken the drug) of either aspirin or NSAIDs. Age, gender, race, education, and smoking habits were accounted for in the analyses.
What were the findings?
There were fewer regular users and frequent users of aspirin in the Parkinson's disease group than the control group. The reduction in the risk of Parkinson's disease in people taking aspirin varied between 11% and 25% when age, gender, race, education, smoking habits, and NSAID use were adjusted for. There were no significant differences in this risk when regularity of use, dose, or duration of use were considered.
There were fewer regular users of NSAIDs in the Parkinson's disease group than the control group. Subgroup analyses suggested that there was a significant decrease in the risk of developing Parkinson's disease in people who had taken NSAIDs regularly, who took between 2 to 14 pills per week or who had taken NSAIDs for over 24 months when age, gender, race, education, smoking habits, and aspirin use were adjusted for. Parkinson's disease remained significant in women, but not in men. The effect of NSAIDs on the risk of Parkinson's disease was no longer significant when the NSAIDs had been taken five years or more prior to diagnosis.
What were the authors' conclusions?
The authors concluded that there is a protective role for NSAIDs in Parkinson's disease, and that further studies are required to investigate this protective effect.
How reliable are the conclusions?
This was a case-control study with broad, but clearly defined, inclusion criteria. The authors stated that they 'marginally' matched participants, and there do seem to be some dissimilarities at baseline. However, it was not reported whether these baseline differences were statistically significant. The inclusion of cases with clinically 'probable' or 'possible' Parkinson's disease (confirmed using set criteria) appears reasonable as Parkinson's disease can be difficult to diagnose accurately. Interviews were conducted by investigators who were blind to disease status. Given that the analysis was based on data from questionnaires that sought information for what may have been a short period of drug usage, at any point in that person's life, there is a potential for recall bias. Results for non-users were classified as non-regular users; it is unclear what impact separating the results for patients who had never used NSAIDs or aspirin would be. It should be noted that the reported risk reductions were based on small numbers of cases and controls suggesting that some caution is required when interpretating the actual significance of the results presented. This study does some limitations, and case control studies can be subject to a number of biases and seldom provide definitive evidence for cause and effect, therefore the recommendation for further research seems appropriate.
Systematic reviews
Information staff at CRD searched for systematic reviews relevant to this topic. Systematic reviews are valuable sources of evidence as they locate, appraise and synthesize all available evidence on a particular topic.
There were no related systematic review identified on the Cochrane Database of Systematic Reviews or on the Database of Abstracts of Reviews of Effects (DARE)
References and resources
1. Ibuprofen wards off Parkinsons. The Sun, 06 November 2007, p10.
2. Painkillers 'cut the risk of Parkinson's'. Daily Express, 06 November 2007, p4.
3. Ibuprofen may cut risk of Parkinsons. The Times, 06 November 2007, p29.
4. Painkillers 'cut brain bug peril'. Daily Mirror, 06 November 2007, p29.
5. Over-the-counter painkillers 'can cut risk of Parkinson's by 60%'. Daily Mail, 06 November 2007, p29.
6. Wahner AD, Bronstein JM, Bordelon YM, Ritz B. Nonsteroidal anti-inflammatory drugs may protect against Parkinson disease. Neurology 2007;69(19):1836-1842.
Consumer information
Parkinson's Disease Society
NHS Direct - Parkinson's disease
British Brain and Spine Foundation - Parkinson's disease and Parkinsonism (PDF file)
Previous Hitting the Headlines summaries on this topic
Painkillers may reduce risk of developing Parkinson's disease. Hitting the Headlines archive, 22 Aug 2003.
'Painkillers may stop Alzheimer's'. Hitting the Headlines archive, 21st July 2003.
Further information about Hitting the Headlines
Further information about Hitting the Headlines, together with selected relevant links, can be found at http://www.library.nhs.uk/hth/.
