Sustained loss of smell due to COVID-19 may better predict long-term cognitive, functional impairment

New insights into factors that may predict, augment or protect the impact of COVID-19 and the pandemic on memory and thinking skills were revealed by multiple studies reported today at the Alzheimer’s Association International Conference® (AAIC)®) 2022 in San Diego and virtually.

Among the key findings reported at AAIC 2022:

  • A group from Argentina found that sustained loss of sense of smell may be a better predictor of long-term cognitive and functional impairment than the severity of initial COVID-19 illness.
  • Intensive care hospitalization was associated with a doubling of dementia risk in older adults, according to a study from the Rush Alzheimer’s Disease Center in Chicago.
  • During the pandemic, female gender, not working and lower socioeconomic status were associated with more cognitive symptoms in a large study population from nine Latin American countries.
  • In that same Hispanic population, experiencing a positive life change during the pandemic (such as more quality time with friends and family or more time in nature) reduced the negative impact of the pandemic on memory and thinking.

“COVID-19 has sickened and killed millions of people around the world, and for some, the emerging research suggests there are long-term effects on memory and thinking as well,” said Heather M. Snyder, Ph.D., vice president. of medical and scientific relations at the Alzheimer’s Association. “As this virus is likely to be with us for a long time, identifying the risk and protective factors for cognitive symptoms could help treat and prevent ‘long COVID’ in the future.”

Persistent loss of smell predicts cognitive impairment better than severity of COVID-19
Researchers in Argentina working with the Alzheimer’s Association Consortium on chronic neuropsychiatric sequelae of SARS-CoV-2 infection followed 766 adults aged 55-95 who had been exposed to COVID-19 for a year and performed a series of regular physical, cognitive and neuropsychiatric tests. Of the study group, 88.4% were infected and 11.6% control group.

Clinical assessment showed functional memory impairment in two-thirds of the infected participants, which was severe in half of them. Another group of cognitive tests identified three groups with impaired performance:

  • 11.7% showed only amnesia.
  • 8.3% had impaired attention and executive functions.
  • 11.6% had a multidomain (including memory, learning, attention and executive function) impairment.

Statistical analysis revealed that persistent loss of smell was a significant predictor of cognitive impairment, but the severity of initial COVID-19 illness was not.

The more insight we have into the causes or at least predict who will experience the significant long-term cognitive impact of a COVID-19 infection, the better we can monitor it and develop methods to prevent it.”

Gabriela Gonzalez-Aleman, LCP, Ph.D., Professor, Pontifical Catholic University of Argentina, Buenos Aires

A stay in the intensive care unit may indicate a higher risk of dementia

Researchers at the Rush Alzheimer’s Disease Center (RADC), part of Chicago’s Rush University System for Health, used data from five different studies of older adults with no known dementia (n=3,822) to observe hospitalizations in the intensive care unit (ICU). ICU hospitalizations have previously been linked to cognitive impairment in elderly patients, but few studies have examined whether they increase the risk of dementia.

They reviewed Medicare claim records from 1991 to 2018 (pre-pandemic) and checked annually for the development of Alzheimer’s disease and all types of dementia using a standardized cognitive assessment. During an average follow-up of 7.8 years, 1,991 (52%) participants experienced at least one ICU hospitalization; 1,031 (27%) had an ICU stay before study enrollment; and 961 (25%) had an ICU stay during the study period.

The researchers found that, in analyzes adjusted for age, gender, education and race, experiencing ICU hospitalization was associated with a 63% higher risk of Alzheimer’s dementia and 71% higher risk of all types of dementia. In models further adjusted for other health factors, such as vascular risk factors and disease, other chronic medical conditions, and functional disabilities, the association was even stronger: ICU hospitalization was associated with 110% greater risk of Alzheimer’s disease and 120% greater risk on all types of dementia.

“We found that hospitalization in intensive care was associated with a doubling of the risk of dementia in older adults in the community,” said Bryan D. James, Ph.D., an epidemiologist at RADC. “These findings may be significant given the high rate of ICU hospitalizations among the elderly, and especially due to the massive increase in ICU hospitalizations during the COVID-19 pandemic. Now more than ever, it is paramount to understand the link between ICU hospitalization and the development of dementia.”

“More research is needed to replicate these findings and elucidate the factors that may increase the risk of dementia. For example, is it the critical illness that sends someone to the hospital or possibly modifiable procedures during hospitalization that increase the risk of dementia.” ?” James added.

One positive life change during the pandemic could buffer cognitive symptoms
Researchers from countries in Central and South America and the United States examined whether sociodemographic factors and life changes associated with the pandemic were associated with experiencing cognitive symptoms, including problems with memory, attention and other thinking skills, during the early phases of the pandemic.

In the study reported by AAIC, 2,382 Hispanic adults ages 55-95 (mean 65.3 years, 62.3% female) from nine countries in Latin America completed an online or telephone survey, underwent electronic cognitive tests, and inventory to assess the positive and negative effects of the pandemic between May and December 2020. Of the total study population, 145 (6.09%) experienced COVID-19 symptoms.

The participants were from: Uruguay (1,423, 59.7%), Mexico (311, 13.1%), Peru (153, 6.4%), Chile (152, 6.4%), Dominican Republic (117 , 4.9%), Argentina (106, 4.5%), Colombia (50, 2.1%), Ecuador (39, 1.6%), Puerto Rico (19, 0.8%) and others ( 12, 0.5%)

Key findings:

  • Female gender, currently unemployed and lower socioeconomic status were all independently associated with more cognitive symptoms during the onset of the pandemic.
  • Negative life changes during the pandemic, such as economic difficulties and limited social activities, were significantly associated with more cognitive symptoms. However, this association was weaker among study participants who reported at least one positive life change during the pandemic, including spending more time with friends and family or more time outside in nature.

“Identifying risk and protective factors for cognitive symptoms during the pandemic is an important step toward developing prevention efforts,” said María Marquine, Ph.D., associate professor in the Departments of Medicine and Psychiatry, and director of research on inequalities in the Division of Geriatrics, Gerontology and Palliative Care at the University of California, San Diego. “The experience of positive life changes during the pandemic could buffer the adverse impact of negative life changes on cognitive symptoms.”

“This study is an example of how researchers from different countries in Latin America and the United States, many of whom had never collaborated before and had limited resources, came together under difficult circumstances, but with a common goal to advance scientific understanding about the Alzheimer’s disease, and the important contributions such multicultural partnerships can make,” Marquine added.

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