Incidence of Newly-Diagnosed Dementia After COVID-19 Infection versus Acute Upper Respiratory Infection: A Retrospective Cohort Study.

Background: There is emerging evidence that coronavirus disease 2019 (COVID-19) is giving rise to seemingly unrelated clinical conditions long after the infection has resolved.

Objective: The aim of this study is to examine whether COVID-19 is associated with an increased risk of dementia including Alzheimer's disease.

Methods: This retrospective cohort study is based on longitudinal data from the IQVIATM Disease Analyzer database and included patients aged≥65 with an initial diagnosis of COVID-19 or acute upper respiratory infection (AURI) from 1,293 general practitioner practices between January 2020 and November 2021. AURI patients were matched 1 : 1 with COVID-19 patients using propensity scores based on sex, age, index quarter, health insurance type, the number of doctor visits, and comorbidities associated with dementia risk. Incidence rates of newly-diagnosed dementia were calculated using the person-years method. Poisson regression models were used to compute the incidence rate ratios (IRR).

Results: The present study included 8,129 matched pairs (mean age 75.1 years, 58.9% females). After 12 months of follow-up, 1.84% of the COVID-19 patients and 1.78% of the AURI patients had been diagnosed with dementia. The Poisson regression model resulted in an IRR of 1.05 (95% CI: 0.85-1.29).

Conclusion: This study did not find any association between COVID-19 infection and one-year dementia incidence after controlling for all common risk factors for dementia. Because dementia is a progressive disease, which can be difficult to diagnose, a longer follow-up period might offer a better insight into a possible association between COVID-19 infection and an increased incidence of dementia cases in the future.