Science

Coronavirus infection could lead to long-term cognitive decline and Alzheimer’s

Global study to investigate whether Covid infection could lead to long-term cognitive decline, Alzheimer’s and dementia YEARS after infection

  • US and UK-based academics are planning a large-scale global study 
  • Will recruit and follow 40,000 people worldwide who have contracted Covid-19  
  • Study will investigate if the viral infection increases risk of cognitive decline  

Scientists are concerned the coronavirus could cause long-term damage to the brain and central nervous system, potentially leading to Alzheimer’s in later life. 

US and UK-based academics are planning a large-scale global study to investigate the possibility SARS-CoV-2, the virus which causes Covid-19, could lead to cognitive decline, Alzheimer’s, Parkinson’s and other forms of dementia years after infection. 

The full repercussions of brain-related problems caused by the coronavirus will not be fully understood for decades as survivors age but autopsies, mouse studies and data from other respiratory viruses are cause for concern, researchers warn. 

There is currently no evidence the coronavirus does cause Alzheimer’s but it has been found the virus is able to invade the brain and scientists hope their global study can shed light on the issue.   

Scientists are concerned the coronavirus could cause severe long-term damage to the brain and central nervous system, potentially leading to Alzheimer’s in later life (stock photo)

‘Since the flu pandemic of 1917 and 1918, many of the flu-like diseases have been associated with brain disorders,’ said lead author Dr Gabriel de Erausquin at the University of Texas. 

‘Those respiratory viruses included H1N1 and SARS-CoV. The SARS-CoV-2 virus, which causes COVID-19, is also known to impact the brain and nervous system.’ 

The research was done in conjunction with British-based experts at the University of Leicester and the Queen’s Medical Centre in Nottingham. 

However, there is lacking data on how viruses impact on long-term cognitive health. 

The Spanish flu of 1918 was tied by scientists to a spike in brain afflictions such as sleep disruption, anxiety and psychosis, symptoms also seen in Covid patients. 

US and UK-based academics are planning a large-scale global study to investigate the possibility SARS-CoV-2, the virus which causes Covid-19, could lead to cognitive decline, Alzheimer's, Parkinson's and other forms of dementia years after infection

US and UK-based academics are planning a large-scale global study to investigate the possibility SARS-CoV-2, the virus which causes Covid-19, could lead to cognitive decline, Alzheimer’s, Parkinson’s and other forms of dementia years after infection 

How coronavirus infects the BRAIN 

The coronavirus can reach the human brain after being inhaled through a person’s nose and getting stuck in their nasal mucus, a study has found. 

It is the first known proof the coronavirus can infect the brain’s neurons via the mucosal pathway.

Throughout the course of the pandemic, it has become clear the coronavirus, called SARS-CoV-2, does not just cause respiratory distress but neurological issues as well. 

For example, one in three report symptoms such as loss of smell or taste, headaches, fatigue, dizziness, and nausea.

Scientists in Germany performed autopsies on 33 patients who died of Covid-19 and studied the mucus at the back of the nose — above the mouth where the throat joins the nasal cavity — as well as samples of brain tissue.

Genetic material of the coronavirus was present in largest quantities in the mucus of the nasal cavity, but SARS-CoV-2’s spike proteins — which protrude from the virus and latch onto human receptors to infect the cells — were also found in the brain.  

Dr Frank Heppner, co-author of the study from Charité–Universitätsmedizin Berlin, says: ‘Once inside the olfactory mucosa, the virus appears to use neuroanatomical connections, such as the olfactory nerve, in order to reach the brain.’

The SARS-CoV-2 pandemic, the researchers write, offers ‘a unique — if unwelcome — opportunity’ to learn more about how viruses damage the brain.  

Previous research has proved the coronavirus can cause delirium, strokes and even paralysis due to its impact on the central nervous system.

However, Dr de Erausquin says the impact will not be limited to these short-term acute symptoms seen in hospitals and will likely manifest into chronic conditions.  

Studies have found that SARS-CoV-2 has been found in brain tissue and experts believe it can attack nerves in the organ. 

The virus is also known to affect the sense of smell in many patients and it is thought it does this because the olfactory bulb in the brain which controls smell is rife with ACE2, the receptor which the virus latches onto in order to infect human cells. 

‘The basic idea of our study is that some of the respiratory viruses have affinity for nervous system cells,’ said senior author Dr Sudha Seshadri, at the University of Texas. 

‘Olfactory cells are very susceptible to viral invasion and are particularly targeted by SARS-CoV-2, and that’s why one of the prominent symptoms of COVID-19 is loss of smell.’ 

Dr Erausquin adds that the virus invades the hippocampus via the olfactory bulb and this part of the brain is integral to memory and learning. 

He says this pathway is thought to be ‘one of the sources’ of the cognitive decline seen in some Covid patients. 

‘We suspect it may also be part of the reason why there will be an accelerated cognitive decline over time in susceptible individuals,’ he adds. 

Writing in the journal Alzheimer’s & Dementia: The Journal of the Alzheimer’s Association, the researchers outline their study plan. 

Scientists in more than 30 countries will follow the lives of around 40,000 participants. 

It will compare people who had the virus with those who did not catch Covid-19 and is being initially funded by the US-based Alzheimer’s Association. 

The first batch of results are not expected until 2022. 

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