New evidence suggested that loss of smell due to COVID-19 could lead to neurological issues like difficulty in concentrating and memory problems.

People infected with COVID-19 usually manifest a number of symptoms, including fever, cough, tiredness, headache, diarrhea, and difficulty in breathing. The disease is also known to cause a sudden loss of smell, a symptom that previous research identified as a possible warning sign for Alzheimer’s disease and other neurological conditions.

But new research suggested that persistent loss of smell after COVID-19 infection could be a predictor of lingering cognitive issues, even more than disease severity.

Presented at the recent Alzheimer’s Association International Conference in San Diego, California by Gabriela Gonzales-Alemán and her colleagues at the Pontifical Catholic University of Argentina in Buenos Aires, the research collected and analyzed data from 766 adults aged 60 years and above who did not have a history of cognitive impairment.

After each of the participants took a PCR test at a COVID testing clinic in Argentina, nearly 90% tested positive for the viral disease.

The researchers collected data on disease severity and provided a sniff test for participants, and a series of cognitive assessments, three months after the COVID test.

The team found that two thirds of the people who tested positive for COVID-19 experienced some form of memory impairment. For half of that group, the memory impairment was severe enough that it interfered with their daily lives.

Gonzales-Alemán also noted that the people who still had complete loss of smell three months post-infection were roughly 1.5 times more likely to have lasting cognitive impairments than those who never experienced it or regained their sense of smell.

According to Frederic Meunier at the University of Queensland in Australia, the findings support the idea that the coronavirus may use the nose to enter the brain.

“Scientists could waste a lot of time looking at other possibilities for how the virus enters the brain, but it seems there is something here that is worth pursuing,” he added.

Gonzalez-Alemán and her colleagues will continue recruiting patients and working with them for four years to gain more insight.