Is long Covid linked to Alzheimer’s disease?

September is World Alzheimer’s Month. This event is run by Alzheimer’s Disease International to raise awareness and challenge the stigma surrounding Alzheimer’s disease (AD) and dementia. AD, a devastating neurodegenerative condition, is a growing global health crisis with profound implications for individuals, families, and society at large. With an ageing population and no cure in sight, the burden of AD is increasing, underscoring the urgency of improved awareness, research, and support for those affected. GlobalData’s epidemiological forecast of AD estimates that total prevalent cases will increase from approximately 36 million cases in 2023 to over 44 million by 2028 in eight major markets (8MM: US, France, Germany, Italy, Spain, UK, Japan, and China). Nearly 50% of these cases will present with moderate to severe AD. According to the Centers for Disease Control and Prevention (CDC), AD is the most common form of dementia. Following the Covid-19 pandemic, people who were infected with the SARS-CoV-2 virus (the virus that causes Covid-19) have reported long-lasting effects such as memory loss and concentration problems, indicating possible brain damage that could lead to an increased risk of dementia.  

A study published in Nature in April 2022 by Douaud and colleagues reported that adults who had Covid-19 suffered brain structure changes after infection. Researchers analyzed 401 brain scans from Covid-19 patients and compared pre-infection scans to post-infection scans (with approximately 141 days separating the Covid-19 diagnosis from the second scan). The imaging showed reductions in grey matter thickness and global brain size, damage in olfactory tissue, and a cognitive decline after Covid-19 illness. Both cognitive decline and reduction in brain size are features of AD, suggesting that over time Covid-19 illness may increase the risk for AD or other types of dementia. Covid-19 has affected millions of people worldwide and the growing evidence of lasting cognitive impairment after Covid-19 illness is concerning, because it could mean a greater number of people developing AD in the next decade. The exact mechanisms underlying the potential link between Covid-19 and Alzheimer’s disease are not fully understood.

Covid-19 has spread to every country and continues to affect people every day, and if a long-term consequence of the virus includes an increased risk of AD, it could lead to a substantial public health crisis. AD already poses a significant burden on healthcare systems and families, and any additional factors that contribute to its prevalence would exacerbate this burden. Findings from recent studies like the one by Douaud and colleagues highlight the importance of ongoing research, monitoring, and public health efforts to address the long-term consequences of the pandemic and to mitigate any additional burdens it may place on individuals and society.