Alzheimer’s disease is signaled by a loss of scent. What if Covid causes you to lose your sense of smell?

One of the strangest Covid the loss of the sense of smell symptoms is one that was thought to be a dementia warning sign even before the epidemic.

The key question for researchers at this point is whether cognitive decline and loss of scent are connected. About 5% of the 27 million Covid patients worldwide have had a loss of smell that has lasted longer than six months.

There may be a connection, according to new preliminary research that was presented on Sunday at the Alzheimers Association International Conference in San Diego, but experts warn that additional study is necessary.

Complete Covid-19 pandemic coverage

Prior studies have revealed that some Covid patients later experience cognitive impairment due to their infection. Researchers in Argentina discovered that, regardless of the severity of the disease, loss of smell during COVID may be a stronger predictor of cognitive impairment in a recent study that has not yet been peer-reviewed.

According to study co-author Gabriela Gonzalez-Aleman, a professor at Pontificia Universidad Catolica Argentina in Buenos Aires, “our data strongly suggest that adults over 60 years of age are more susceptible to cognitive impairment post-Covid if they had a smell dysfunction, regardless of the severity of the Covid,” adding that it’s too soon to tell if the cognitive impairment is permanent.

Following their infection, the study followed 766 adults, aged 55 to 95, for a year. Over the course of a year, all participants underwent routine physical, cognitive, and neuropsychiatric examinations and nearly 90% had a verified case of Covid.

By the end of that year, two thirds of those afflicted had some form of cognitive impairment. Half of the subjects had a severe disability.

The researchers asked participants’ relatives about their cognitive function prior to infection but did not include persons who had obvious cognitive impairment prior to the study because they lacked hard data on the state of the patients’ cognitive function to compare with the results at the end.

Smell loss is a well-established indicator of cognitive decline, according to Jonas Olofsson, a psychology professor at the University of Stockholm who researches the relationship between sense of smell and dementia risk and was not part in the new study. It’s also generally known that Covid might cause a permanent loss of smell, he added.

According to Olofsson, the issue is if these two areas of study cross paths. The information I have seen so far from this study is pretty intriguing, yet it prevents me from drawing any firm conclusions.


Loss of smell is an indication of an inflammatory reaction in the brain, claims Dr. Claire Sexton, senior director of scientific initiatives and outreach at the Alzheimer’s Association.

According to Sexton, inflammation is a known contributor to the neurodegenerative process in conditions like Alzheimer’s. However, we must delve more into their precise connections.

The relationship is further explored in a different study, unrelated to Covid, that was published last Thursday in the journal Alzheimers andamp; Dementia. Researchers at the University of Chicago discovered that losing one’s sense of smell can serve as a warning sign of structural changes in brain regions crucial to the development of dementia and Alzheimer’s disease. Not only can a decline in one’s sense of smell over time predict the loss of cognitive function.

The researchers monitored the loss of scent in 515 older persons over a 22-year period using data from Rush University’s Memory and Aging Project. Additionally, they evaluated the amount of gray matter in the brain regions connected to scent and dementia.

They discovered that individuals whose sense of smell deteriorated more quickly over time had less gray matter in both of these areas of the brain. The same was not true of brain regions associated with vision, indicating that sense of smell has a special relationship to cognition in terms of structural variations.

According to study leader Dr. Jayant Pinto, director of Rhinology and Allergy at UChicago Medicine, changes in olfactory function over time can predict not just the onset of dementia but also the size of those crucial brain regions.


Although Covid is not the first virus to induce loss of smell, Pinto noted that the condition was uncommon before the epidemic. Thus, scientists have only recently had the capacity to carry out extensive research on the potential effects of smell loss brought on by a virus on cognition.

The sense of smell is crucial for cognition, particularly for the brain’s ability to process environmental information. The brain will suffer if that line of communication is cut off, according to Dr. Carlos Pardo, a neurology professor at Johns Hopkins University who was not involved in either study.

It’s unknown, however, if a lack of smell brought on by COVID can affect cognition.

Is there any evidence that the damage caused by SARS-CoV-2 to the olfactory system affects the brain as a whole, in addition to the olfactory system? said Pinto.

For comprehensive coverage of the Covid-19 epidemic, download the NBC News app.

Olofsson asserts that the olfactory system, which includes the olfactory bulb, the area of the brain responsible for processing scent, relates to regions of the brain responsible for remembering. Olofsson said it’s not likely that Covid disturbs the olfactory bulb, which would cause the brain to degrade surrounding it.

These two items can be connected in a variety of various ways. According to him, the pathology may be the cause rather than the Covid effect.

According to Olofsson, Covid may also merely increase any existing loss of smell or cognitive deterioration that was there before to the infection. Patients may have had experienced mild olfactory system impairment or cognitive decline prior to contracting Covid, making them more vulnerable to smell loss brought on by Covid.

It’s possible that the olfactory function was still functioning despite the atrophic state, but that when Covid arrived, it was destroyed.

If it turns out that smell loss in Covid can lead to cognitive impairment, knowing the link could aid doctors in intervening with smell loss early and possibly halting cognitive decline in high-risk individuals.

Pardo stated that we will have to deal with the persistent spread of a virus. We may be able to reduce the harm that loss of scent may bring with cognitive problems in persons who are susceptible if we learn more about how we are able to recover smell rapidly.

Health on NBC
Based on Twitter and Facebook.