Persistent smell loss after SARS-CoV-2 infection predicted cognitive impairment in older adults, a longitudinal study in Argentina has shown.
One year after acute infection, anosmia was more strongly associated with cognitive impairment than with severity of SARS-CoV-2 infection, reported Gabriela Gonzalez-Aleman, MSc, PhD, of the Pontificia Universidad Católica Argentina in Buenos Aires, during the 2022 Alzheimer’s Association International Conference.
“The more we know about the causes or at least predict who will experience the significant long-term cognitive impact of COVID-19 infection, the better we can track it and begin to develop methods to prevent it,” said Gonzalez-Aleman.
The findings are part of a world brain study Chronic Neuropsychiatric Sequelae of COVID, a consortium of researchers led by the Alzheimer’s Association and representatives from over 25 countries with technical guidance from the World Health Organization (WHO).
“We are learning more every day about the connection between COVID-19 and the brain,” noted Claire Sexton, PhD, senior director of science programs and outreach at the Alzheimer’s Association. “Loss of smell is often a sign of an inflammatory response in the brain. We know that inflammation is part of the neurodegenerative process in diseases like Alzheimer’s disease.”
“With other viruses, such as SARS and MERS, there have been similar associations between infection and cognition, but there are still big questions about cause and effect,” Sexton pointed out.
The Argentine study followed 865 people over the age of 60 recruited from a provincial health registry that included all SARS-CoV-2 testing data for the region. The researchers randomly invited older adults with a positive COVID PCR test to participate between 3 and 6 months after acute SARS-CoV-2 infection.
The assessments followed the recommendations of the global consortium and included the WHO Annexes for Clinical Assessment in Neuropsychiatry (TO ANALYSE), the Clinical Dementia Rating Scale, neurocognitive and emotional reactivity ratings, and semi-quantitative ratings of olfactory function, motor function, coordination, and gait.
Of the 865 participants, 84.2% had COVID and 15.8% were controls with no history of a positive SARS-CoV-2 test. The median age was 67 and just over half (56.5%) were female. Participants had a median of 10.35 years of schooling. Most participants with COVID had no serious infection, with very few (2% or less) admitted to intensive care.
At 1 year, about a quarter of the study sample had no cognitive impairment; that group included control participants and about 20% of post-COVID patients, Gonzalez-Aleman said. The scores of the remaining participants were normalized to the mean of the cognitively normal group, with impairment defined as z-scores less than -2. The remaining participants were grouped into groups based on deficits in memory, attention, executive function and language, with some showing impairment in more than one area.
PCR status and age predicted post-COVID cognitive problems, Gonzalez-Aleman said. Logistic regression analyzes showed that the severity of anosmia, but not the severity of SARS-CoV-2 infection, was significantly associated with cognitive impairment.
All of the anosmia has been reported after acute SARS-CoV-2 infection, Gonzalez-Aleman noted. Some people in the control group also had anosmia, but their olfactory dysfunction was much less common — and less severe — than that of the participants with COVID, she added.
The findings are part of ongoing research on COVID among older Native American adults in Argentina. “It’s important to provide the public with the most up-to-date research so we can be aware of the evolving ways in which this virus affects us,” Sexton said.
“But it’s also worth pointing out that a lot more research is needed to paint a fuller picture of what COVID-19 is doing to our bodies and brains,” she added. “We also need to study the direct impact that 2 years of pandemic-related isolation has had on our health.”
The research was supported by the Alzheimer’s Association and the FULTA Foundation.
Gonzalez-Aleman did not disclose any relationship with the industry.