THE pandemic is leading to a surge in dementia cases in Scotland amid growing evidence about how Covid-19 'attacks the brain'.

One of the main symptoms of the virus - the loss of sense of taste and smell - is neurological and experts say it is unclear if there is more lasting cognitive impairment.

A number of studies are underway looking at the impact of Covid on the brain, led by Dr Alan Carson, Professor of Neuropsychiatry at Edinburgh University. He said there was already 'good data' showing that in the six months after Covid infections there is an increase in dementia cases.

However, he said this was only the case where patients had developed delirium - where patients with viral infections become disorientated - but he said Covid was causing this to happen more frequently and unusually in those under 65.

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Alzheimer Scotland has previously warned that social isolation and lack of supports is accelerating symptoms in those who have already been diagnosed with dementia, including people with milder forms of the illness.

Paola Barbarino, Chief Executive of the Alzheimer Disease International, a global umbrella group of 100 Alzheimer's association, said "we should be worried" because there is so much scientists don't yet know about the impact of the virus on the brain. 

She said: "We know that the external manifestation (of Covid-19) is that lack of breath and respiratory problems but we are now realising that there is a much bigger damage to the brain."

Dr Carson, who is involved with the Centre for Clinical Brain Sciences at the University of Edinburgh, said he was particularly interested in the impact of 'Long Covid', which he said it unlikely to one condition but a variety of complications of viral infection.

He said: "My particular interest is on cognitive symptoms, so problems with memory or concentration, thinking or judgement. Quite a few patients have identified these neuro-psychiatric symptoms among the most common and disabling consequences.

"I think they will range from one end, patients with precipitated dementia illnesses to at the other end, anxiety.

READ MORE: Covid service pressures blamed for 75% rise in women with dementia dying at home 

"With regard to dementia, we know that the processes of dementia probably start ten to 20 years before the illness becomes clinically apparent.

"We know if you develop delirium, where your body gets a sort of inflammatory response leading to the infection that it can cause an impact on the brain, such that you become disorientated and don't know what date it is, where you are etc.

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"We already know that this has a bad effect on brains if they about to suffer from Alzheimer disease or already are. You advance several years in the same number of weeks.

"There is good data showing that in the six months after Covid infection there is an increased rate of dementia but only those patients who develop delirium.

"That is exactly what we would predict from what we already know about delirium. The thing that is unusual is that Covid is causing this to happen more frequently than other respiratory viruses.

"It would be very rare for us to see somebody delirious coming into hospital with influenza under 65 but that happens quite frequently with Covid.

He said that the evidence that Covid is leading to more dementia cases is "clear cut" but added: "I do worry that we have jumped forward to thinking that everything with Covid must be novel rather than thinking what do we already know about some of these conditions but that's not to say that those studies shouldn't be done."

Paola Barbarino, Chief Executive of the Alzheimer Disease International, said it is probable that there will be an initial statistical decline in dementia rates globally due to significant mortality in the population and the impact of disruption to diagnoses.

Deaths due to Covid-19 among people living with dementia as a proportion of the population have been estimated to be as high as 26 percent in the UK. 

However she said referrals are likely to rise in the coming months saying the impact of Covid on neurological conditions had been "the greatest by far of any other underlying condition".

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"It's clear that one of the things that Covid-19 attacks is the brain," she said. "One of the symptoms is loss of sense of taste and smell which is a neurological problem. So then you have to consider if this is having an impact that will last a longer time.

"There seems to be three main mechanisms of Covid. There is direct brain invasion of Covid and that seems to lead to sense of smell and taste loss.

"Then, there seems to be something related to the brain/blood barrier. So there is something that prevents the blood going into the brain caused by Covid.

READ MORE: 'Devastating impact': Concern over increase in care home admissions as support networks collapse in pandemic

"Then there is some kind of inflammation mechanism that we don't yet understand. There are other things, like there may be micro-vascular damage.

"There are studies that suggest that there is quite a lot going on in the brain that needs further investigation and this is exactly what we are looking at now.

"We already know that anything that diminishes one's cognitive reserve is going to allow a degenerative disorder to accelerate. 

"There is still so much we don't know about how the brain works but it seems quite obvious that there will be a correlation.

She added: "I think we should be worried and it is really, really important that one tries not to catch Covid even those in the categories deemed not to be at risk.

"We don't really know what the long-term effects are on the brain, which is such a complicated organ."

The Herald is backing Alzheimer Scotland's campaign for fairer care home fees for people living with advanced dementia