COVID-19 Infection May Up New-Onset Alzheimer Disease Risk in Older Adults

COVID-19 infection is associated with an increased risk of developing new-onset Alzheimer disease (AD) in patients aged 85 years or older, with women demonstrating the highest risk, according to an observational retrospective study published in the Journal of Alzheimer’s Disease.

COVID-19 infection increases inflammatory processes which may lead to long lasting neurological sequelae. Inflammatory processes also are key factors in the pathogenesis of AD; however, the ability of COVID-19 infection to provoke new onset AD is unknown.

Researchers at Case Western Reserve University conducted a retrospective cohort study analyzing data from medical encounters between February 2020 and May 2021 to assess the incidence of new-onset AD within 360 days following COVID-19 infection in patients aged 65 years or older.

Of the 6,245,282 patients aged 65 years or older with medical encounters during this period, 410,748 had confirmed COVID-19 infection, while 5,834,534 did not have COVID-19. The researchers balanced the COVID-19 cohort (mean age, 73.7 years; 53.6% women; 75.3% White) with the non-COVID control group using 1:1 propensity matching. In the COVID-19 cohort, comorbidities included hypertension (59.4%); overweight and obesity (23%); and type 2 diabetes (30.4%).

They used the TriNetX Analytics Platform to confirm newly diagnosed AD based on ICD-10 codes and laboratory tests obtained from medical records documented within 360 days following COVID-19 infection.

The researchers found that adults aged 65 years or older demonstrated a 0.68% increased risk for new-onset AD within 360 days after COVID-19 infection compared with a 0.35% risk in the control group (hazard ratio [HR], 1.69; 95% CI, 1.53-1.72).

Increased risk for new-onset AD occurred more frequently in specific subgroups, especially in women (HR, 1.82; 95% CI, 1.69-1.97) and those aged 85 years or older (HR, 1.89; 95% CI, 1.73-2.07). While the researchers also analyzed subgroups classified by race or ethnicity, this factor did not significantly increase risk for new-onset AD after COVID-19 infection.

The researchers emphasized that the observational nature of the study does not provide evidence to suggest that COVID-19 causes AD.

Study limitations included the potential misdiagnosis of Alzheimer’s disease.

“Our findings call for research to understand the underlying mechanisms and for continued surveillance of long-term impacts of COVID-19 on Alzheimer’s disease,” the researchers acknowledged.

They concluded that “Next steps include validation from other data resources, longer-term follow-up, mechanism understanding and examining other types of dementia.”