Cognitive decline in older adults during and after the COVID-19 pandemic: a longitudinal analysis of the PROTECT UK study data

Abstract

Background: Whilst the long-term health effects of COVID-19 infection are increasingly recognised, the societal restrictions during the pandemic hold the potential for considerable detriment to cognitive and mental health, particularly since major dementia risk factors such as exercise and dietary habits were impacted during this period. This study utilises longitudinal data from the PROTECT study to evaluate the impact of the pandemic on cognition in older adults in the UK. Methods: A longitudinal analysis of data from people aged 50 and over in the PROTECT study using computerised neuropsychology data collected before the pandemic (March 2019-2020) and during its first (March 2020-2021) and second year (March 2021-2022), with the same participants at each timepoint. Cognition was compared across the three time periods using a mixed linear model. Sub-group analyses were conducted in people with MCI and COVID-19 infection, and an exploratory regression analysis identified factors associated with change in cognitive trajectory. Findings: Executive function (Effect Size [ES] 0.15) and working memory (ES0.51) showed significant worsening across the whole cohort in the first year of the pandemic and in people with MCI (ES0.23 and 0.14) and COVID-19 (ES0.24, 0.46). Worsening in working memory was sustained in the second year (ES0.47). Regression analysis indicated that reduced exercise (P=0.005), increased alcohol use (P=0.05) and poor mental health (P=0.005) were significantly associated with decline, with sustained associations in people with MCI and COVID-19 in the second year. Interpretation: The pandemic has resulted in a significant worsening of cognition in older adults, associated with changes in known dementia risk factors. The sustained decline highlights the need for public health interventions to mitigate dementia risk, particularly in people with MCI where conversion to dementia within five years is a substantial risk. There is a need to consider long-term intervention for people with COVID-19 to support cognitive health.