Early, Midlife Hospital-treated Infections may Increase risk of Parkinson's disease

SWEDEN: According to a recent study published in PLOS Medicine, infections requiring specialized medical care are linked to a higher risk of Parkinson's disease later in life. Alzheimer's disease was also found to have an elevated risk, but not amyotrophic lateral sclerosis (ALS).

Progressive neuronal loss in the neurological systems is a hallmark of neurodegenerative disorders like Alzheimer's disease (AD), Parkinson's disease (PD), and amyotrophic lateral sclerosis (ALS). The causation of neurodegenerative illness may be influenced by infection, according to experimental data. It is challenging to determine in human research if an infection is a risk factor, comorbidity, or secondary event of neurodegenerative illness.

The three most prevalent neurodegenerative disorders were evaluated in relation to prior inpatient or outpatient bouts of hospital-treated infections by the authors.

Data from individuals with Parkinson's disease, Alzheimer's disease, and ALS who were identified from the National Patient Register and were diagnosed in Sweden between 1970 and 2016 were examined by a study team from the Karolinska Institute in Sweden. Five people who matched the case's sex and age were randomly chosen to act as controls for each instance.The analysis included 103,919 cases of Parkinson's disease, 291,941 cases of Alzheimer's disease, and 10,161 cases of ALS. The median age at diagnosis for Parkinson's disease was 74.3, and the median age at diagnosis for Alzheimer's disease was 76.2. Because there may be complicating circumstances, infections that occurred five years or less before a diagnosis of a neurodegenerative disease were disregarded. The patient's sex, year of birth, place of residence, educational level, family history of neurodegenerative illness, and an index of comorbidities were all taken into account when adjusting the results.

Key highlights of the study:

• A hospital-treated infection that occurred five years or more before the diagnosis of a neurological disease was connected to a 4% increased chance of acquiring Parkinson's. No matter if the infection was bacterial, viral, or another kind, the danger persisted. Additionally, the risk for infections in the gastrointestinal and genitourinary systems of the body was the same.
• The chance of acquiring Parkinson's disease was more than 40% higher in people who had repeated infections that required hospital care before the age of 40.
• Alzheimer's disease risk was also shown to be higher. In patients with one hospital-treated infection five years or more before the disease diagnosis, it was 16% higher, and in patients with several infections prior to the age of 40, it was more than twice as high. For ALS, no connection was found.

The research findings, that hospital-treated infections were more strongly associated with risk of AD and PD before 60 years of age, as compared to later, and that people who experienced repeated infections in their early and mid-life had the highest risk increment of AD and PD, according to the researchers, are novel and potentially significant.

The researchers concluded that the underlying processes for the association between infections and neurodegenerative illness may not be specific to certain pathogens or damaged organs but rather could take place at the systemic level.

According to them, infectious episodes may act as a catalyst or amplifying factor for an underlying disease process, causing neurodegenerative illness to manifest clinically at a young age in people who are predisposed to the condition.

REFERENCE

Sun J, Ludvigsson JF, Ingre C, Piehl F, Wirdefeldt K, Zagai U, Ye W, Fang F. 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. PLoS Med. 2022 Sep 15;19(9):e1004092. doi:10.1371/journal.pmed.1004092. PMID: 36107840; PMCID: PMC9477309.