The Association of Pre-existing Diagnoses of Alzheimer's Disease and Parkinson's Disease and Coronavirus Disease 2019 Infection, Severity and Mortality: Results From the Korean National Health Insurance Database.

Objectives: Despite the numerous studies on coronavirus disease 2019 (COVID-19), data regarding the impact of pre-existing diagnoses of Alzheimer's disease (AD) and Parkinson's disease (PD) on the susceptibility to and outcome of COVID-19 are limited. We aimed to determine whether patients with AD/PD had a higher likelihood of contracting COVID-19 and experiencing worse outcomes.

Methods: Data from patients with confirmed diagnoses of COVID-19 ( = 8,070) from January to June 2020 and control participants ( = 121,050) who were randomly selected to match the patients on the basis of age and sex were extracted from the Korean National Health Insurance Database. Pre-existing diagnoses of AD and PD were identified based on medical claim codes. The associations of pre-existing AD or PD with contracting COVID-19, developing severe COVID-19 and dying due to COVID-19 were examined using a logistic regression model. The participants' age, sex, income, comorbidity score, and history of hypertension/diabetes were assessed as covariates.

Results: COVID-19 cases were more likely to have a pre-existing AD diagnosis (adjusted odds ratio [aOR] = 2.11, 95% confidence interval [CI] = 1.79-2.50, -value < 0.001) than controls. COVID-19 cases were more likely to have a pre-existing PD diagnosis than controls, although this estimate did not quite reach statistical significance (aOR = 1.41, 95% CI = 1.00-2.00, -value = 0.054). Pre-existing AD was related to severe disease and mortality from COVID-19 (aOR = 2.21, 95% CI = 1.64-2.98; aOR = 2.21, 95% CI = 1.00-2.00). Pre-existing PD was not associated with mortality (aOR = 1.54, 95% CI = 0.75-3.16) but was associated with severe disease (aOR = 2.89, 95% CI = 1.56-5.35).

Conclusion: We found that COVID-19 infection was significantly associated with a pre-existing diagnosis of AD but not with a pre-existing diagnosis of PD. Patients with pre-existing AD had higher odds of developing severe COVID-19 and dying. Pre-existing PD was only associated with a higher odds of developing severe COVID-19.