According to a new study, infections treated with specialty hospital care in early and mid-life are related with an elevated risk of Alzheimer’s (AD) and Parkinson’s diseases (PD), but not amyotrophic lateral sclerosis (ALS).
Animal studies have shown that infection has a role in the development of various neurodegenerative disorders, but human data is lacking.
In the new study, researchers used data on people diagnosed with AD, PD or ALS from 1970-2016 in Sweden and five matched controls per case, all identified from the Swedish National Patient Register. The analysis included 291,941 AD cases, 103,919 PD cases and 10,161 ALS cases. A hospital-treated infection 5 or more years before diagnosis was associated with a 16% higher risk of AD (95%CI: 1.15-1.18, P < 0.001) and a 4% higher risk of PD (95%CI: 1.02-1.06, P < 0.001), with similar risks seen for bacterial, viral and other infections and for different sites of infection.
The highest risk of disease was seen in people with multiple hospital-treated infections before the age of 40, with more than double the risk of AD (OR=2.62, 95%CI: 2.52-2.72, P < 0.001) and more than 40% increase in the risk of PD (OR=1.41, 95%CI: 1.29-1.53, 3 44 P < 0.001). No association was observed for ALS, regardless of age at diagnosis.
“These findings suggest that 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,” the authors say, while also pointing out that “due to the observational nature of the study, these results do not formally prove a causal link.”
Sun adds, “Hospital-treated infections, especially in early- and mid-life, were associated with an increased risk of Alzheimer’s disease (AD) and Parkinson’s disease (PD), primarily among AD and PD cases diagnosed before 60 years.”