The risk of some neurological and psychiatric conditions (such as dementia, psychosis and seizures) remains higher two years after Covid-19 compared to other respiratory infections, an observational study of

more than 1.25 million patient health records

suggests. published in

The Lancet Psychiatry

.

The increased risk of depression and anxiety in adults lasts less than two months before returning to rates comparable to other respiratory infections.

Since the start of the pandemic, there has been increasing evidence that survivors may be at increased risk of neurological and psychiatric problems

.

An earlier observational study by the same research group reported that Covid-19 survivors are at increased risk of various neurological and mental conditions in the first six months after infection.

Until now , however,

there have been no large-scale data examining the risks of these diagnoses over a longer period of time.

This study is also the first on a large scale to examine the risk of suffering from these types of conditions after Covid infection in children and to evaluate how the risks change with the appearance of new variants.

Professor Paul Harrison, lead author of the study, from the University of Oxford, UK, said: "In addition to confirming previous findings that Covid may increase the risk of some neurological and psychiatric conditions in the first six months after infection,

this study suggests that some of these increased risks may last for at least two years.The

results have important implications for patients and healthcare services, as they suggest that

new cases of infection-related neurological conditions are likely to occur by Covid-19 for a considerable time after the pandemic has subsided

.

Our work also highlights the need for more research to understand why this is happening after Covid, and what can be done to prevent or treat these conditions."

Sample and analysis

The study analyzed data on

14 neurological and psychiatric diagnoses collected

from electronic health records mostly from the US over a two-year period.

Of the people with health records in the US-based TriNetX network,

1,284,437 had a confirmed SARS-CoV-2 infection as of January 20, 2020

and were included in the study: 185,748 children (under 18 years old), 856,588 adults between 18 and 64 years old, and 242,101 adults over 65 years old.

These individuals were matched with an equal number of patients with another respiratory infection to act as a control group.

Records of Covid patients infected during different pandemic waves were also compared to investigate differences in the impact of alpha, delta, and omicron variants

on the risk of neurological and psychiatric diagnoses.

People who had a first diagnosis of Covid within the period in which a specific variant was dominant (alpha: 47,675 people, delta: 44,835 people, omicron: 39,845 people) were compared with a control group of the same number of individuals who had a first diagnosis of Covid in the period just before the appearance of this variant.

Depression and anxiety

The study found that, in adults,

the risk of having a diagnosis of depression or anxiety initially increased after SARS-CoV-2 infection, but returned to the same as with other respiratory infections after a relatively short time

(depression) .

at 43 days, anxiety at 58 days).

After the initial increase, the risks of being diagnosed with depression or anxiety fell below those of the control group, meaning that,

after two years, there was no difference in the overall incidence of depression and anxiety between the Covid group -19 and other respiratory infections

(In adults aged 18 to 64 in both groups, in the two years after infection, there were about 1,100 cases of depression per 10,000 people and about 1,800 cases of anxiety per 10,000 people).

However, the risk of diagnosis of some other neurological and mental health conditions was still higher after Covid than for other respiratory infections at the end of two years of follow-up.

Adults aged 18 to 64 who had had Covid up to two years earlier had a higher risk of cognitive deficits, or

brain fog

(640 cases per 10,000 people), and muscle disease (44 cases per 10,000), compared to those who had other respiratory infections up to two years earlier (550 cases per 10,000 people for "brain fog" and 32 cases per 10,000 for muscle disease).

In adults aged 65 and over who had had Covid up to two years earlier, there was a higher incidence of

brain fog

(1,540 cases per 10,000 people), dementia (450 cases per 10,000 people), and psychotic disorder (85 cases per 10,000 people) compared with those who had previously suffered from another respiratory infection (1,230 cases per 10,000

brain fog

, 330 cases per 10,000 of dementia and 60 cases per 10,000 of psychotic disorder).

The likelihood of most post-Covid neurological and psychiatric diagnoses was lower in children than in adults

, and they were not at greater risk of anxiety or depression than children who had other respiratory infections.

However, like adults, children were more likely to be diagnosed with some conditions, including seizures

(260 cases per 10,000 children for the Covid-19 group; 130 cases per 10,000 for the control group) and disorders. psychotic (18 cases per 10,000 children for the Covid group; 6 cases per 10,000 for the control group), during the two years following infection.

With the new variants

Little change in the risks of neurological and psychiatric diagnoses was observed six months after Covid, just before and after the appearance of the alpha variant

.

However, the appearance of the

delta variant was associated with significantly higher risks at six months of anxiety

(10% increased risk), insomnia (19% increased risk), cognitive deficits (38% increased risk) , epilepsy or seizures (26% increased risk) and ischemic strokes (27% increased risk), but a lower risk of dementia (40% decreased risk) compared with those diagnosed with Covid just prior to death delta wave.

The risks during omicron were similar to those when the delta variant was dominant.

"Our findings shed new light on the long-term consequences for people's brain and mental health following Covid-19 infection. It is good news that the increased risk of post-infection depression and anxiety diagnoses is relatively short-lived." and that there is no increased risk of these diagnoses in children. However, it

is concerning that some other conditions, such as dementia and seizures, continue to be diagnosed more frequently after Covid infection, even two years later

," says Dr. Max Taquet of the University of Oxford, who led the analyses.

"The appearance of the delta variant was associated with an increased risk of several conditions; however,

it is important to note that the overall risk of these conditions remains low

.

With omicron as the dominant variant, although we see much milder symptoms directly after infection, we see similar rates of neurological and psychiatric diagnoses as with delta, suggesting that

the burden on the healthcare system may continue even with variants that are less severe in other respects

."

More resources and support for health workers

The researchers call for the results of their study to serve as a basis for health clinics and public health policy

.

This study suggests that an increase in the number of new Covid cases is likely to lead to a relatively short-lived increase in the number of mood and anxiety conditions, which means that

mental health professionals need to be prepared and equipped with good resources after a wave of Covid-19

.

Furthermore, the sustained increase in risk of some neurological and psychiatric diagnoses over the two years following Covid indicates that patients and clinicians need to remain alert to the possibility of these delayed conditions.

Health facilities must be well supported to diagnose and treat these neurological and mental conditions, as new cases are likely to occur for a considerable time after the pandemic has subsided.

The authors warn that some important limitations must be taken into account, such as that the study may underestimate self-diagnosed and asymptomatic cases of Covid, since they are unlikely to be included in electronic health records.

In addition, they did not analyze the severity or duration of each condition after diagnosis or whether these are similar after Covid than after other respiratory infections.

Dr Jonathan Rogers and Professor Glyn Lewis, from University College London (who were not involved in the study), say:

"As we emerge from the acute phase of the pandemic, it is critical to understand whether the resulting disability risks are transient. or persistent

.

The answer offered by this research -at least during a follow-up period of two years- is that it depends on the neurological or psychiatric outcome that interests us.

This study is the first to attempt to examine some of the heterogeneity of persistent neurological and psychiatric aspects of Covid in a large data set.

It highlights some clinical features that are especially worthy of further investigation, but should be complemented by prospective studies that provide further validation of the results."

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