Persistent loss of smell after COVID predicts cognitive impairment

Persistent loss of smell after SARS-CoV-2 infection predicted cognitive impairment in older adults, longitudinal study in Argentina showed.

One year after acute infection, anosmia was more strongly associated with cognitive impairment than SARS-CoV-2 infection severity, reported Gabriela Gonzalez-Aleman, MSc, PhD, of the Pontificia Universidad Católica Argentina in Buenos Aires, at the International Conference of the Alzheimer’s Association 2022.

“The more insight we have into the causes, or at least predict who will experience the significant long-term cognitive effects of COVID-19 infection, the better we can track them and start developing methods to prevent them,” Gonzalez-Aleman said .

The findings are part of a global brain study on chronic neuropsychiatric sequelae of COVID, a consortium of researchers led by the Alzheimer’s Association and representatives from more than 25 countries, with expert guidance from the World Health Organization (WHO).

“We’re learning more about the connection between COVID-19 and the brain every day,” noted Claire Sexton, PhD, senior director of scientific programs and outreach at the Alzheimer’s Association. “Loss of smell is often a signal for an inflammatory response in the brain. We know that inflammation is part of the neurodegenerative process in diseases like Alzheimer’s.”

“Other viruses, such as SARS and MERS, have had 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 who were recruited from a provincial health registry that contained all SARS-CoV-2 test data for the region. Researchers randomly invited older adults with a positive PCR-COVID test to participate between 3 and 6 months after acute SARS-CoV-2 infection.

The assessments followed recommendations from the global consortium and included the WHO SCAN (Schedules for Clinical Assessment in Neuropsychiatry) scale, the Dementia Clinical Rating Scale, neurocognitive and emotional reactivity ratings, and ratings of semi-quantitative olfactory function, motor function, coordination and gait.

Among 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 years and just over half (56.5%) were female. Participants had a median of 10.35 years of education. Most participants with COVID did not have a severe infection, with very few (2% or less) admitted to the ICU.

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 e.g-Values ​​below -2. The remaining participants were divided into groups based on memory, attention, executive functioning, and language deficits, with some individuals showing impairments in multiple domains.

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 anosmias were 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 that we are aware of the evolving impact this virus is having on us,” Sexton said.

“But it’s also worth noting that much more research is needed to paint a more complete picture of what COVID-19 is doing to our bodies and brains,” she added. “We also need to examine the direct impact that two years of pandemic-related isolation has had on our health.”