Jiangwei Sun Ph Postdoctoral researcher in Prof. Jonas Ludvigsson's group Department of Medical Epidemiology and Biostatistics Karolinska Institutet

Hospital-Treated Infections And Risk of Later Life Neurodegenerative Diseases

MedicalResearch.com Interview with:

Jiangwei Sun Ph Postdoctoral researcher in Prof. Jonas Ludvigsson's group Department of Medical Epidemiology and Biostatistics Karolinska Institutet

Dr. Sun

Jiangwei Sun PhD
Postdoctoral researcher
in Prof. Jonas Ludvigsson’s group
Department of Medical Epidemiology and Biostatistics
Karolinska Institutet

MedicalResearch.com: What is the background for this study?

Response: A potential infectious etiology has been hypothesized for neurodegenerative diseases, as findings in animal studies have demonstrated that infectious processes might impact pathogenesis, phenotype, and progression of neurodegenerative disease.

The extrapolation of such findings to a human context is however not straightforward. previous studies have mostly examined the role of specific pathogens on a specific neurodegenerative disease, e.g., herpesvirus for Alzheimer’s disease, and influenza, hepatitis C virus, and Helicobacter pylori for PD, with inconclusive results. Although several studies have also assessed associations between infectious diseases and risk of dementia and AD, influence of potential surveillance bias (greater-than-expected surveillance of disease after infections) and reverse causation (due to for example diagnostic delay of neurodegenerative diseases) on the associations was not always fully addressed.

Therefore, whether infection is indeed a risk factor rather a comorbidity or secondary event of neurodegenerative disease remains unknown. In contrast to Alzheimer’s disease, and Parkinson’s disease, the potential link between infection and ALS has been less explored.

MedicalResearch.com: What are the main findings?

  • Infections treated in specialized care were associated with an increased subsequent risk of Alzheimer’s disease, and Parkinson’s disease – primarily AD and PD diagnosed before 60 years, but not ALS. These positive associations remained after excluding infections experienced within 10 years before diagnosis of AD or PD.
  • Increased risks of Alzheimer’s disease, and Parkinson’s disease were observed for bacterial, viral, and other infections, and across different sites of infection, including central nervous system, gastrointestinal, and genitourinary infections.
  • Individuals with repeated infections in early- and mid-life had the greatest risk increment of AD and PD.

MedicalResearch.com: Any particular types of infections?

Response:  Unlike most previous studies, our study did not focus on specific infectious diseases (e.g., influenza, pneumonia, or viral hepatitis), but instead studied all infections requiring hospital treatment. To our knowledge, it is the first to date to assess the associations of hospital-treated infections – by type, site, age, and frequency – with risks of the three most common neurodegenerative diseases in the same population.

MedicalResearch.com: What should readers take away from your report?

The underlying mechanisms for the link between infections and neurodegenerative disease may not be specific to certain pathogens or affected organs but possibly occur at the systemic level.

  • Infectious events may be a trigger or amplifier of a pre-existing disease process, leading to clinical onset of neurodegenerative disease at a relatively early age among individuals with disease predisposition.

MedicalResearch.com: What recommendations do you have for future research as a results of this study?

Response: Further studies are warranted to validate these findings, to elucidate underlying mechanisms, and to determine whether better control of hospital-treated infections could prevent or delay onset of neurodegenerative diseases, especially the ones with an onset relatively early in life.


Hospital-treated infections in early- and mid-life and risk of Alzheimer’s disease, Parkinson’s disease, and amyotrophic lateral sclerosis: A nationwide nested case-control study in Sweden.

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