Study findings updated . AI-assisted evidence summary, not individual medical advice or a clinician endorsement.
THE SHORT VERSION
What’s worth knowing.
The key findings, what they mean, and the context that matters.
THE HEADLINE TAKEAWAY71 more per 1,000Extra people per 1,000 with a new neurologic diagnosis in the year after COVID-19
COVID-19 was linked to more brain and nerve disorders a year later.
Among US veterans who survived the first month of COVID-19, about 71 more per 1,000 had a new neurologic diagnosis within a year than uninfected veterans from the same period. Problems ranged from stroke and memory trouble to seizures, nerve damage and Guillain-Barré syndrome. Risks rose even in people never hospitalized.
With so many Americans infected, a few dozen extra cases per 1,000 people adds up to a very large number with stroke, memory or nerve problems, and the risk was not limited to the very sick. Based on health records of mostly white male veterans, so results may differ for women and other groups, and the links do not prove COVID-19 was the cause.
See the evidence
A US Veterans Affairs health-records study comparing 154,068 people who had COVID-19 with millions of uninfected veterans, tracking new diagnoses for about a year.
From the study: “Compared with the contemporary control group, there was increased risk and burden of any neurologic outcome (HR 1.42 (1.38, 1.47); burden 70.69 (63.54, 78.01)), respectively.”
71 more per 1,000
Xu E et al. Long-term neurologic outcomes of COVID-19. Nature medicine. 2022.
Guillain-Barré risk was higher after COVID-19 infection than after vaccination.
145 more per 10 millionExtra Guillain-Barré cases within 28 days of a positive test; 38 after AstraZeneca
Among people vaccinated in England, the 28 days after a positive COVID-19 test brought about 145 extra cases of Guillain-Barré syndrome (a nerve disorder causing weakness) per 10 million people. A first AstraZeneca dose brought 38 extra per 10 million; a first Pfizer dose brought no rise in it. Each person was compared with their own other time periods.
Weighing vaccine side effects means weighing the other side too: in this study, infection itself carried a bigger risk of this rare nerve disorder, and of several other brain complications, than the shots. Data come from England between December 2020 and May 2021; the AstraZeneca shot is not used in the US, and Pfizer was tied to a small, less certain rise in brain bleeds.
See the evidence
A self-controlled study of hospital records for over 32 million vaccinated people in England, comparing each person's risk in the weeks after a shot or a positive test with other times.
From the study: “Overall, we estimated 38 excess cases of Guillain-Barré syndrome per 10 million people receiving ChAdOx1nCoV-19 and 145 excess cases per 10 million people after a positive SARS-CoV-2 test.”
145 more per 10 million
Patone M et al. Neurological complications after first dose of COVID-19 vaccines and SARS-CoV-2 infection. Nature medicine. 2021.
From the study: “Also, an increased risk of Guillain–Barré syndrome was observed in the 1–28 days period after a SARS-CoV-2-positive test (IRR, 5.25; 95% CI: 3.00–9.18).”
145 more per 10 million
Patone M et al. Neurological complications after first dose of COVID-19 vaccines and SARS-CoV-2 infection. Nature medicine. 2021.
Stroke risk roughly tripled in the first two weeks after COVID-19.
3.0× stroke riskIschemic stroke rate in the first week after COVID-19 vs. other times (rate ratio)
Across all COVID-19 cases in Sweden early in the pandemic, ischemic stroke (a clot blocking blood flow to the brain) struck at about 3.0 times the usual rate in the first week after infection and 2.8 times in the second, compared with other periods in the same people's lives. Strokes stayed rare: under 1 per 1000 people.
The weeks right after infection are a window of higher danger: sudden face drooping, arm weakness or trouble speaking during that time calls for emergency help, not waiting it out. Data come from February to September 2020, before vaccines and newer variants, and the number of strokes in each window was small, so estimates are imprecise.
See the evidence
A national Swedish registry study of all 86,742 people diagnosed with COVID-19 from February to September 2020, comparing stroke rates before and after infection.
From the study: “The corresponding IRRs for ischaemic stroke when day of exposure was excluded from the risk period were 2·97 (1·71-5·15) in the first week, 2·80 (1·60-4·88) in the second week”
3.0× stroke risk
Katsoularis I et al. Risk of acute myocardial infarction and ischaemic stroke following COVID-19 in Sweden: a self-controlled case series and matched cohort study. Lancet (London, England). 2021.
From the study: “the absolute risks among both patients with COVID-19 and controls of acute myocardial infarction and ischaemic stroke obtained in the matched cohort study are less than 1 per 1000 people.”
3.0× stroke risk
Katsoularis I et al. Risk of acute myocardial infarction and ischaemic stroke following COVID-19 in Sweden: a self-controlled case series and matched cohort study. Lancet (London, England). 2021.
Brain fog and dementia risks stayed raised two years after COVID-19.
Still higher at 2 yearsBrain fog, dementia and seizure risk after COVID-19 vs. other respiratory infections
Compared with matched patients who had another respiratory infection, people with COVID-19 were still more likely to get new diagnoses of brain fog, dementia, psychotic disorders and seizures at the end of 2 years. Extra risks of mood and anxiety disorders faded within 1-2 months. In children, the extra brain fog risk faded after 75 days.
Comparing with other respiratory infections shows these risks are not just what any illness does, and risks with Omicron looked similar to those just before it, despite a lower death rate. Built from doctors' diagnosis codes, it shows links rather than proof of cause, and fewer people were followed all the way to 2 years.
See the evidence
A health-records study, mostly from the US, of 1,284,437 people with COVID-19 matched to people with other respiratory infections, diagnosed from 2020 to 2022.
From the study: “By contrast, risks of cognitive deficit (known as brain fog), dementia, psychotic disorders, and epilepsy or seizures were still increased at the end of the 2-year follow-up period.”
Still higher at 2 years
Taquet M et al. Neurological and psychiatric risk trajectories after SARS-CoV-2 infection: an analysis of 2-year retrospective cohort studies including 1 284 437 patients. The lancet. Psychiatry. 2022.
From the study: “Risks of the common psychiatric disorders returned to baseline after 1-2 months (mood disorders at 43 days, anxiety disorders at 58 days)”
Still higher at 2 years
Taquet M et al. Neurological and psychiatric risk trajectories after SARS-CoV-2 infection: an analysis of 2-year retrospective cohort studies including 1 284 437 patients. The lancet. Psychiatry. 2022.
From the study: “Unlike adults, cognitive deficit in children had a finite risk horizon (75 days) and a finite time to equal incidence (491 days).”
Still higher at 2 years
Taquet M et al. Neurological and psychiatric risk trajectories after SARS-CoV-2 infection: an analysis of 2-year retrospective cohort studies including 1 284 437 patients. The lancet. Psychiatry. 2022.
Even mild, resolved COVID-19 was linked to slightly lower test scores.
About 3 IQ points lowerAverage gap in thinking tests after short, fully resolved COVID-19 vs. no COVID-19
In a large English community study, adults whose COVID-19 symptoms had fully cleared scored slightly lower on online thinking and memory tests than people with no confirmed COVID-19, a gap the authors equate to about 3 IQ points. People with lingering symptoms showed bigger gaps, and those treated in intensive care about 9 points.
A small average dip goes unnoticed by most people, but across millions of infections it matters, and the gap grew with lingering symptoms and severe illness. Online tests at one point in time cannot prove cause, and gaps were largest for early-pandemic variants and much smaller for later ones.
See the evidence
An online study in England in which 112,964 adults, with and without past COVID-19, completed eight thinking and memory tasks.
From the study: “this would equate to -3 points on a standard 15-point IQ scale.”
About 3 IQ points lower
Hampshire A et al. Cognition and Memory after Covid-19 in a Large Community Sample. The New England journal of medicine. 2024.
From the study: “Larger deficits were seen in participants who had SARS-CoV-2 infection during periods in which the original virus or the B.1.1.7 variant was predominant than in those infected with later variants”
About 3 IQ points lower
Hampshire A et al. Cognition and Memory after Covid-19 in a Large Community Sample. The New England journal of medicine. 2024.
Brain scans showed extra shrinkage in smell-linked areas after COVID-19.
0.7% extra tissue lossAdded shrinkage in smell-linked brain areas after mostly mild COVID-19 vs. uninfected
Middle-aged and older UK adults scanned before and after catching COVID-19 lost on average 0.7% more tissue in smell-linked brain regions than uninfected people scanned on the same schedule. Infected people also showed more decline on thinking tests. The changes held after removing the 15 people who had been hospitalized.
Because everyone had a scan before getting sick, pre-existing differences are a less likely explanation than in most brain studies. Whether these changes fade over time is not yet known. An observational study of 785 mostly white UK adults infected early in the pandemic; it cannot prove cause, and not every infected person showed these average changes.
See the evidence
A UK Biobank study that scanned 785 people aged 51 to 81 twice, about 3 years apart, comparing 401 who caught COVID-19 in between with 384 who did not.
From the study: “This additional loss in the infected participants of 0.7% on average across the olfactory-related brain regions”
0.7% extra tissue loss
Douaud G et al. SARS-CoV-2 is associated with changes in brain structure in UK Biobank. Nature. 2022.
From the study: “Importantly, these imaging and cognitive longitudinal effects were still observed after excluding the 15 patients who had been hospitalised.”
0.7% extra tissue loss
Douaud G et al. SARS-CoV-2 is associated with changes in brain structure in UK Biobank. Nature. 2022.
One-on-one coaching helped people with long COVID brain fog reach goals.
2.9 points higherGain on a 1–10 personal goal scale with one-on-one rehab vs. usual care at 3 months
In an English trial, adults with long COVID and measurable thinking problems who got 10 weekly one-hour sessions of goal-focused rehabilitation scored 2.9 points higher on a 1-to-10 scale of personal goals at 3 months than those on usual care. Researchers count a 2-point gain as meaningful.
With no proven treatments for long COVID brain fog, this is a rare positive trial; the benefit was still clear at 6 months, though fatigue and mood did not improve. A small trial of 78 people who knew their group, with goals rated by participants; a larger US trial of computer brain training and a structured rehab program found no edge over puzzles.
See the evidence
A randomized trial at 3 sites in England in 2023 to 2024 that assigned 78 adults aged 30 to 60 with long COVID thinking problems to rehabilitation or usual care.
From the study: “At 3 months after randomization, goal attainment was significantly greater in the CR compared with the TAU group (adjusted mean difference, 2.88 [95% CI, 2.03-3.73]; P < .001; Cohen d = 1.57)”
2.9 points higher
Vanova M et al. Cognitive Rehabilitation and Functional Outcomes in Long COVID-Related Cognitive Impairment: A Randomized Clinical Trial. JAMA network open. 2026.
From the study: “The BGSI goal-attainment scale rates each goal 1 to 10 points (low to high), with an improvement of 2 or more points considered clinically meaningful.”
2.9 points higher
Vanova M et al. Cognitive Rehabilitation and Functional Outcomes in Long COVID-Related Cognitive Impairment: A Randomized Clinical Trial. JAMA network open. 2026.
From the study: “CR consisted of 10 individual 1-hour sessions conducted once per week with a trained researcher”
2.9 points higher
Vanova M et al. Cognitive Rehabilitation and Functional Outcomes in Long COVID-Related Cognitive Impairment: A Randomized Clinical Trial. JAMA network open. 2026.
COVID-19 in pregnancy was not linked to baby development delays.
No delays by 18 monthsDevelopment screens of babies exposed to COVID-19 in the womb matched unexposed babies
In a US study of 1179 enrolled participants, babies whose mothers had COVID-19 in pregnancy scored no differently on standard parent-reported development and autism screening checklists at 12 and 18 months than babies of uninfected mothers. Results held across virus variants and pregnancy trimesters.
Many families who caught COVID-19 while pregnant have worried about their child's brain. This large, diverse US study offers reassurance for the first year and a half, while longer follow-up continues. Most exposures happened during Omicron and later in pregnancy, and parent-filled screening checklists can miss subtle differences that later testing might find.
See the evidence
Part of the RECOVER Pregnancy Cohort, which followed babies born from 2020 to 2023 at 23 US sites, comparing those exposed to COVID-19 before birth with unexposed babies.
From the study: “Among 1179 participants enrolled, 1008 (85.5%) had exposure, with 806 (80.0%) exposed during Omicron predominance.”
No delays by 18 months
Flaherman VJ et al. Intrauterine SARS-CoV-2 Exposure and Infant Neurodevelopment through 18 Months of Age: Findings from the Researching COVID to Enhance Recovery (RECOVER) Pregnancy Study. The Journal of pediatrics. 2026.
From the study: “Neurodevelopment was assessed at 12 months with the Ages & Stages Questionnaire, 3rd edition (ASQ-3) and at 18 months with the ASQ Social-Emotional (ASQ-SE)”
No delays by 18 months
Flaherman VJ et al. Intrauterine SARS-CoV-2 Exposure and Infant Neurodevelopment through 18 Months of Age: Findings from the Researching COVID to Enhance Recovery (RECOVER) Pregnancy Study. The Journal of pediatrics. 2026.
From the study: “intrauterine SARS-CoV-2 exposure was not associated with neurodevelopmental screening outcomes through 18 months of age.”
No delays by 18 months
Flaherman VJ et al. Intrauterine SARS-CoV-2 Exposure and Infant Neurodevelopment through 18 Months of Age: Findings from the Researching COVID to Enhance Recovery (RECOVER) Pregnancy Study. The Journal of pediatrics. 2026.
Recorded COVID was linked to dementia and stroke diagnoses in older adults with diabetes
Older adults with type 2 diabetes and documented COVID-19 had higher hazards of dementia, vascular dementia and a type of stroke (cerebral infarction) than matched unexposed adults.
Adults were aged ≥65. Dementia analyses used a 1-year checkpoint and a later 3-year checkpoint. Mild problems with thinking (mild cognitive impairment) and Alzheimer’s disease also had higher hazard estimates, but their comparison groups are not given here. Hazards are rates over time. Matching cannot show cause; undocumented infections could be missed.
Study details & original results
Chen, I-Wen et al.. Long-term risk of incident dementia following documented COVID-19 among older adults with type 2 diabetes: a propensity score-matched cohort study.. Frontiers in aging neuroscience. 2026.
Incident overall dementia after the 1-year landmark among adults aged ≥65 years with T2DM and documented COVID-19 versus matched unexposed adults
HR 1.51 95% CI: 1.47-1.55
Vascular dementia among older adults with T2DM and documented COVID-19 versus matched unexposed adults
HR 1.61
Mild cognitive impairment following documented COVID-19 among matched older adults with T2DM (p<0.001)
HR 1.66
Alzheimer's disease following documented COVID-19 among matched older adults with T2DM (p<0.001)
HR 1.41
Overall dementia among propensity score-matched older adults with T2DM and documented COVID-19 versus unexposed adults at the 3-year sequential landmark period
HR 2.09
Cerebral infarction among older adults with T2DM and documented COVID-19 versus matched unexposed adults
Memory difficulties, fatigue and sleep problems were tracked after hospital care
Among adults previously hospitalized for COVID-19, 47-61% reported memory or concentration difficulty at checks through 36 months. Fatigue and sleep problems were also reported.
The percentage varied across checks; it does not mean the same people had uninterrupted symptoms. These were previously hospitalized adults. The findings do not show that fatigue or sleep problems caused thinking difficulties.
Dizziness and problems with coordination became more common after hospitalization
Dizziness and difficulty with coordination became more common over 36 months after COVID-19 hospitalization. Fatigue was also reported alongside other symptoms affecting the nervous system.
These were different symptoms in previously hospitalized people. The findings do not show that everyone had the same combination or that one symptom caused another.
Study details & original results
Lee, Eunyoung A et al.. Longitudinal trajectories of neurologic symptoms and cognitive associations at 36-months post-hospitalization for COVID-19.. Frontiers in neurology. 2026.
Memory/concentration difficulty prevalence across follow-up assessments through 36 months among adults previously hospitalized for COVID-19
47-61%
Fatigue prevalence across follow-up assessments through 36 months among adults previously hospitalized for COVID-19
53-65%
Sleep-disturbance prevalence across follow-up assessments through 36 months among adults previously hospitalized for COVID-19
Thinking ability changed in different ways after Omicron hospitalization
22.0% (460/2087)
Two years after leaving hospital, 22.0% of Omicron survivors had a decline in thinking ability that reversed; 67.1% stayed stable. The study reported 10.8% whose decline did not reverse and 3.6% whose decline kept worsening.
How these decline categories overlap is not given here. Their percentages should not be added or used to predict an individual’s recovery. These findings concern people who survived hospitalization.
Age and vaccine-dose count were linked to worsening thinking ability
Age ≥60 years was linked to higher odds of thinking ability that kept worsening after Omicron infection. The number of vaccine doses was linked to lower odds of that decline.
The age comparison group and vaccine-dose comparison are not given here, so the numerical odds are omitted. These links do not show that vaccination prevented the decline.
Study details & original results
Qiu, Min et al.. Post-Omicron cognitive decline is largely reversible: Two-year multicenter cohort study of domain-specific outcomes in hospitalized patients.. Neuroprotection (Chichester, England). 2026.
Hospitalized post-Omicron survivors with reversible cognitive decline by two years after discharge
22.0% (460/2087)
Hospitalized post-Omicron survivors who maintained stable cognitive function two years after discharge
67.1% (1401/2087)
Hospitalized post-Omicron survivors with irreversible cognitive decline two years after discharge
10.8% (226/2087)
Hospitalized post-Omicron survivors who showed progressive cognitive decline by two years
The review counted brain fog and problems with thinking separately
30%
In Long COVID groups, a review combined estimates of brain fog in 30% and problems with thinking (cognitive impairment) in 25%. Each was more common in females than males.
The two outcomes were reported separately, so their percentages cannot be added. Definitions and follow-up periods are not given here. The comparisons between females and males do not explain why the estimates differ.
Study details & original results
Faseeh, Ahmar et al.. Prevalence and long-term outcomes of brain fog and cognitive impairment in individuals with long COVID: A systematic review.. Medicine. 2026.
Pooled prevalence of brain fog in long COVID populations
30% 95% CI: 28-32
Pooled prevalence of cognitive impairment in long COVID populations
25% 95% CI: 23-27
Cognitive impairment prevalence by gender - females vs males
Dates show when findings were added here, not when papers were published. Study populations and comparisons differ.
WHEN YOU WANT TO GO DEEPERSee all 22 findingsOriginal results, comparisons and study details.
4 of 4 source groupsFindings stay together with their study.
SOURCE 056 findings
Chen, I-Wen et al.. Long-term risk of incident dementia following documented COVID-19 among older adults with type 2 diabetes: a propensity score-matched cohort study.. Frontiers in aging neuroscience. 2026.
Overall dementia among propensity score-matched older adults with T2DM and documented COVID-19 versus unexposed adults at the 3-year sequential landmark period
Lee, Eunyoung A et al.. Longitudinal trajectories of neurologic symptoms and cognitive associations at 36-months post-hospitalization for COVID-19.. Frontiers in neurology. 2026.
Qiu, Min et al.. Post-Omicron cognitive decline is largely reversible: Two-year multicenter cohort study of domain-specific outcomes in hospitalized patients.. Neuroprotection (Chichester, England). 2026.
Faseeh, Ahmar et al.. Prevalence and long-term outcomes of brain fog and cognitive impairment in individuals with long COVID: A systematic review.. Medicine. 2026.
Browse the 13 original sourcesThe complete bibliography behind this monitor.
[1]
Faseeh, Ahmar et al.. Prevalence and long-term outcomes of brain fog and cognitive impairment in individuals with long COVID: A systematic review.. Medicine. 2026.
Qiu, Min et al.. Post-Omicron cognitive decline is largely reversible: Two-year multicenter cohort study of domain-specific outcomes in hospitalized patients.. Neuroprotection (Chichester, England). 2026.
Lee, Eunyoung A et al.. Longitudinal trajectories of neurologic symptoms and cognitive associations at 36-months post-hospitalization for COVID-19.. Frontiers in neurology. 2026.
Luo, Xue et al.. Cognitive function among COVID-19 survivors in the subacute phase during the epidemic of Omicron variant in China.. Journal of Zhejiang University. Science. B. 2026.
Chen, I-Wen et al.. Long-term risk of incident dementia following documented COVID-19 among older adults with type 2 diabetes: a propensity score-matched cohort study.. Frontiers in aging neuroscience. 2026.
Katsoularis I et al. Risk of acute myocardial infarction and ischaemic stroke following COVID-19 in Sweden: a self-controlled case series and matched cohort study. Lancet (London, England). 2021.
Taquet M et al. Neurological and psychiatric risk trajectories after SARS-CoV-2 infection: an analysis of 2-year retrospective cohort studies including 1 284 437 patients. The lancet. Psychiatry. 2022.
Vanova M et al. Cognitive Rehabilitation and Functional Outcomes in Long COVID-Related Cognitive Impairment: A Randomized Clinical Trial. JAMA network open. 2026.
Flaherman VJ et al. Intrauterine SARS-CoV-2 Exposure and Infant Neurodevelopment through 18 Months of Age: Findings from the Researching COVID to Enhance Recovery (RECOVER) Pregnancy Study. The Journal of pediatrics. 2026.
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