As populations around the globe age, dementia -; often caused by Alzheimer's disease and related disorders -; is a growing health issue for older adults worldwide. Although it may not seem like COVID-19 has much in common with these disorders, Penn State College of Medicine researchers say that these diseases may be linked to each other.
A $1.6 million grant from the National Institute of Neurological Disorders and Stroke will support research into whether COVID-19 contributes to the development of cognitive decline that may be part of the chain of events leading to dementia.
Epidemiologists at the Centers for Disease Control and Prevention estimate that just under one third of all COVID-19 cases have occurred in individuals aged 50 years and older. This same group also is at increased risk for either having or developing a neurodegenerative disease. COVID-19 patients often report neurological symptoms like memory issues, "brain fog," and loss of smell and taste -; with some symptoms lasting months after diagnosis. Some research also suggests that these patients are at higher risk of being diagnosed with dementia following their acute infection. These and other reports have led to scientific speculation that COVID-19 infections may be contributing to premature cognitive decline, said the researchers.
To study whether there is a connection between COVID-19 infection and neurocognitive decline, Dr. Xuemei Huang, distinguished professor of neurology, pharmacology, neurosurgery, radiology and kinesiology at the College of Medicine and chief of the Division of Movement Disorders at Penn State Health Milton S. Hershey Medical Center, will lead a multidisciplinary team to gather additional information and biological samples from participants in their past and ongoing studies. The study will leverage the resources from a multiyear, $3.8 million project that aims to identify biological signs (biomarkers) of Parkinson's disease and related disorders through magnetic resonance imaging (MRI) scans and molecules in biological samples including blood, skin and cerebral spinal fluid.
"We have a unique opportunity to study whether COVID-19 infection contributes to the progression of neurodegenerative diseases," said Huang, who also directs the Translational Brain Research Center. "Parkinson's disease and related disorders often lead to dementia at the end, and we hope to gain a better understanding of whether COVID-19 infection affects the process of neurocognitive decline in our research participants."
In the same way that loss of smell has signaled COVID-19 infection for some individuals, some scientists theorize that loss of smell also signals the beginning of neurodegenerative processes that lead to both Parkinson's and Alzheimer's diseases. This may come from a person's continued exposure to viruses and environmental toxicants that enter via the olfactory system (nose and nasal passages) -; a concept known as the olfactory vector hypothesis of neurodegenerative disease. SARS-CoV-2, the virus that causes COVID-19, is one example of a virus that enters the body via the olfactory system.
The research team will collect information about COVID-19 infection history, vaccination status, ongoing environmental toxin exposure, medical history and other lifestyle factors from more than 500 participants of their past and ongoing research studies -; some with Parkinson's disease and related disorders and some who are healthy. Huang's team has data from these participants that were collected before the current pandemic. The team will use MRI brain scans to identify possible changes in brain anatomy similar to those that occur in Parkinson's disease, and also look for blood markers that occur in neurodegeneration.
We're still learning about the long-term effects of the pandemic and the effects on those who became ill. This research will increase our understanding of whether or not COVID-19 infection contributes to the development or progression of neurodegenerative diseases."
Xuemei Huang, distinguished professor of neurology, pharmacology, neurosurgery, radiology and kinesiology, College of Medicine and chief of the Division of Movement Disorders, Penn State Health Milton S. Hershey Medical Center