All-Cause Dementia, Alzheimer Disease Are Independent Risk Factors for COVID-19 Severity, Death


The findings suggest that patients with dementia should be prioritized for stringent preventive measures, greater surveillance, and early intervention in COVID-19.

In a cohort of community-dwelling individuals older than 65 years tested for COVID-19, researchers highlighted the prominent role of all-cause dementia, and in particular Alzheimer disease (AD), as an independent risk factor for worse COVID-19 disease severity and death. 

Lead author Ana Tahira, PhD, postdoctoral researcher, Institute of Psychiatry, University of Sao Paulo, and colleagues collected data from 12,863 UK Biobank individuals to assess the impact of dementia on COVID-19 outcomes, including higher infection rates and disease severity. Among the cohort, 1167 individuals were COVID-19-positive and 11,696 were negative. 

At initial analysis, the researchers found a number of risk factors associated with higher risk of COVID-19 diagnosis, including all-cause dementia, AD, and Parkinson disease (PD). Several of these risk factors remained significant in a multivariate stepwise regression model, notably age (odds ratio [OR], 1.019; 95% CI, 1.004-1.034; P = .011), AD (OR, 5.700; 95% CI, 3.709-8.762; P <.001), PD (OR, 2.242; 95% CI, 1.511-3,328; P <.001) and other forms of dementia (OR, 3.412; 95% CI, 2.234-5.213; P <.001), indicating that patients with these conditions are at a higher risk of positive diagnosis of COVID-19.

"While shielding these patients from infection may prove challenging due to their inherent need of caregivers and difficult in adhering to strict personal health-care measures, these results suggest that patients with all-cause dementia should receive special attention upon hospitalization to prevent evolution of the disease to a potentially irreversible condition,” Tahira et al wrote. 

READ MORE: Increased Mortality in Patients With COVID-19 Neurological Symptoms

Within the analytical sample, 6232 individuals were hospitalized and 6631 were not between March 16 , 2020 and August 24, 2020. All-cause dementia, AD, or PD were not among the risk factors associated with higher overall risk of hospitalization; however, all-cause dementia (OR, 3.929; 95% CI, 2.650-5.772; P <.001), AD (OR, 5.789; 95% CI, 3.088-10.856; P <.001), and PD (OR, 2.001; 95% CI, 1.240-3.127; P = .003) were associated with higher risk of COVID-19-related hospitalization using a subgroup of 932 hospitalized patients with COVID-19 compared with 5300 inpatients without COVID-19 diagnosis. 

Univariable analysis that used death as a dependent variable showed that all-cause dementia (OR, 2.171; 95% CI, 1.231-3.900; P = .008) and AD (OR, 2.766; 95% CI, 1.123-7.420; P = .032) were associated with higher risk of COVID-19-related death independent of age.

In a stepwise multivariate analysis, AD (OR, 2.814; 95% CI, 1.095-7.233; P = .032) and African ethnicity were associated with higher risk of death in COVID-19-positive inpatients, while cancer events were associated with lower risk. 

Tahira and colleagues observed a significant interaction between all-cause dementia and age for COVID-19 positive diagnosis (OR, 1.16; 95% CI, 1.03-1.22; P = .010) after building 3 different interaction multivariate models. The models used all-cause dementia, AD, or PD as independent categorical variables and age as a continuous numerical independent variable, and COVID-19-positive diagnosis as a dependent variable.

"Remarkably, whereas several factors were found to be associated with increased overall risk of death in the studied cohort, only few variables, including all-cause dementia (and AD in particular), were found to be specifically associated with higher risk of COVID-19–related death,” the study authors wrote. “Of note, we further found that all-cause dementia remained significantly associated with increased death risk in the oldest (80 years old and older) individuals positive for SARS-CoV-2.”

Tahira AC, Almeida SV, Ferreira ST. Dementia is an age-independent risk factor for severity and death in COVID-19 inpatients. Alzheimers Dement. Published online April 21, 2021. doi: 10.1002/alz.12352
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