Journal watch: Long-term risk of parkinson disease following influenza and other infections

Journal watch: Long-term risk of Parkinson disease following influenza and other infections

2560 1700 Maggie Ford, MD
The Background

The connections between prior influenza and other infections to the risk of developing Parkinson disease (PD) have been contentious.1

 

The Objective

This case-control study addresses the association between influenza and other infections and the long-term risk for the development of PD.1

 

The Strategy

For this study 10 271 PD cases were selected from the Denmark national health care databases with 51 355 controls being selected from the Danish Civil Registration System.1 The study used 5:1 matching without replacement based on age and sex.1 The authors then used the data from the Danish National Patient Registry to calculate case and control exposures to influenza and other infections (including but not limited to pneumonia, gastrointestinal infection, Herpes simplex or zoster, septicemia, viral hepatitis, upper respiratory tract infection, urinary tract infection, heart infection, and intra-abdominal infection) from 1977 through 2016.1

For the statistical analysis, conditional logistic regression was used to calculate adjusted odds ratios with associated 95% confidence intervals.1 Adjustments were made for the presence of cardiovascular disease, diabetes, Crohn’s disease, and ulcerative colitis as they are associated with increased risk of PD.2,3 Adjustments were also made for smoking as it is associated with a decreased risk of PD.2,3

 

The Findings

This study revealed that individuals who had been diagnosed with influenza at any point in a given calendar year had a 73% increased risk of being diagnosed with PD, more than 10 years after the initial infection (P=0.02).1 In addition, individuals who had been diagnosed with other infections (including but not limited to pneumonia, gastrointestinal infection, Herpes simplex or zoster, septicemia, viral hepatitis, upper respiratory tract infection, urinary tract infection, heart infection, and intra-abdominal infection) had a 4% increased risk of being diagnosed with PD, more than 10 years after the initial infection (P>0.05).1

 

The Future

Further studies are needed to investigate if influenza infection causes PD, because case control studies like the present study are only designed to measure potential associations between an exposure and a disease and not causality.1

 

The Conclusion

Because this study found an increased risk of PD diagnosis more than 10 years after influenza infection, this suggests that influenza infection could be a risk factor for PD.1

 


References
  1. Cocoros NM et al. JAMA Neurol. 2021;78(12):1461-1470
  2. Wirdefeldt K et al. Eur J Epidemiol. 2011;26(suppl 1):S1-S58
  3. Lee H-S et al. 2021;70(2):408-417.
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