Long-term effects of COVID-19 infection may shape cognitive health in an aging society

By Neil Charness, Ph.D., Director, Institute for Successful Longevity

We are already very aware of the risk of death associated with contracting COVID-19 for aging adults. Older adults age 65+, who comprise a bit more than 16% of the population in the USA, suffered almost 75% of all deaths from COVID-19 (https://data.cdc.gov/widgets/9bhg-hcku?mobile_redirect=true ). However, a more insidious problem is beginning to be recognized for those who survive COVID-19 infection: impaired cognition. A recently published study of Chinese survivors who were age 60 and older examined cognitive status at 6 months and then a year following infection, https://jamanetwork.com/journals/jamaneurology/fullarticle/2789919 . The researchers compared those who fell into categories of severe Covid and non-severe Covid to controls who were not treated for COVID-19, usually uninfected spouses. What they found is striking.

For all analyses, having a severe case was associated with worse outcomes than having a non-severe case. For instance, decline at six months occurred for 61% of severe cases compared to 29% of non-severe cases and for 21% of control cases. In the second six months, 31% of severe cases had cognitive decline, compared to 5% in less severe cases and 5% in the control participants.  The fact that the cognitive deficit appears to diminish over time, perhaps similar to other conditions such as “chemo brain” https://www.washingtonpost.com/health/2022/03/27/covid-brain-fog-chemo-brain-alzheimers-disease/ provides some guarded optimism.

In another analysis they classified people into different trajectories: stable cognition, early-onset cognitive decline, late-onset cognitive decline, and progressive cognitive decline. Even non-severe cases showed a 70% higher risk of early-onset cognitive decline (odds ratio of 1.71) compared to the total group, and severe cases had a 487% greater risk (odds ratio of 4.87). For other categories, the non-severe group did not differ much from the controls (late-onset, progressive decline), but the severe case group had very-high risk ratios.

What does this mean for our aging population? Clearly, getting a severe case of COVID-19 when you are older not only jeopardizes your life but also increases your risk for dementia if you do survive. We know that approved vaccines plus their boosters are highly protective against severe Covid (and for preventing death). For the roughly 11% of Americans age 65+ who are not fully vaccinated https://www.cdc.gov/coronavirus/2019-ncov/covid-data/covidview/index.html the much higher risk of developing dementia after infection may be a very good reason to do so. On the bright side, 95% of those age 65+ have had at least one dose of vaccine. The case of contracting non-severe Covid is also alarming for the long-term mental health of our aging population. It is estimated that 43% of Americans have been infected with COVID-19, https://covid.cdc.gov/covid-data-tracker/#national-lab. That represents 140 million Americans. Now, the Chinese study did not follow those younger than age 60. So, we don’t know if those with non-severe COVID-19 at younger ages have the same risk of later showing abnormal cognitive decline rates in their older years. But, that prospect of greater vulnerability to dementia is worrisome and should be an incentive for everyone, young and old alike, to become fully vaccinated.

We experienced a decline in dementia rates in the population in the last decade or so, though we can expect the total number of cases to rise despite the lower prevalence rate simply because so many people are aging into the high dementia risk years, for instance, the 70-million strong Baby Boom cohort. If there is even a tiny increased risk associated with contracting dementia after COVID-19 infection in younger cohorts, those dementia prevalence numbers could move higher. And there are probably a significant number of younger and middle-aged Americans who have survived severe COVID-19 infections who might have an elevated risk of impaired cognition as they age. This analysis suggests that it will be important to monitor the long-term effects of the pandemic on the cognitive health of our aging population.  Hopefully, by the time younger age cohorts reach their high-risk years, we will have effective interventions to mitigate both normal and abnormal cognitive aging.