Many large epidemiological studies demonstrate a correlation between cardiovascular aging and the risk of suffering cognitive decline and dementia. The population size of such studies has increased in recent years with the advent of sizable national databases, such as the UK Biobank. Today's open access paper focuses on one specific aspect of cardiovascular aging, the onset of atrial fibrillation, irregular heartbeats that can be accompanied by palpitations and other worrying sensations. Atrial fibrillation can arise in combination with many of the features of cardiovascular aging, and one might argue that data on time of diagnosis is interesting because the physical sensation of atrial fibrillation might more readily drive people to see a physician (and thus become a row in a database) than is the case for other early manifestations of declining heart function.
Regardless of that speculation, the researchers demonstrated that earlier diagnosis of atrial fibrillation, indicative in some fraction of cases that other cardiovascular issues are present, is associated with increased risk of suffering later dementia. The brain is an energy-hungry organ, and cardiovascular aging can imply reduced blood flow to the brain, a lower supply of nutrients that has consequences over the long term. That cardiovascular aging associated is typically also accompanied by a greater decline in quality of blood vessels and higher blood pressure, leading to damage and rupture of small vessels in the brain. There are numerous other mechanisms that likely contribute meaningfully to the link between heart, circulation, and brain, of course: nothing is ever simple in the biology of aging.
To examine whether age at atrial fibrillation (AF) diagnosis is associated with risk of incident dementia and its subtypes, this prospective, population-based cohort study used data from UK Biobank, a public, open-access database in the UK with baseline information collected from 2006 to 2010. A total of 433,746 participants were included in the main analysis after excluding participants with a diagnosis of dementia or AF at baseline, missing data on covariates, or having dementia before AF onset during a median follow-up of 12.6 years. Data were analyzed from October to December 2022.
Our research showed that AF participants had an elevated risk of subsequent dementia compared with participants without AF. More importantly, multivariate Cox regression models indicated that an earlier diagnosis of AF was associated with greater risks of incident all-cause dementia, Alzheimer's disease (AD), and vascular dementia (VD). Additionally, the results remained robust after propensity score matching, reinforcing the fact that the probability of developing dementia increases with a younger onset age of AF.
Compared with individuals without AF, 30,601 individuals with AF had a higher risk of developing all-cause dementia (adjusted hazard ratio [HR], 1.42). Among participants with AF, younger age at AF onset was associated with higher risks of developing all-cause dementia (adjusted HR per 10-year decrease, 1.23), AD (adjusted HR per 10-year decrease, 1.27), and VD (adjusted HR per 10-year decrease, 1.35). After propensity score matching, individuals with AF diagnosed before age 65 years had the highest HR of developing all-cause dementia (adjusted HR, 1.82), followed by AF diagnosed at age 65 to 74 years (adjusted HR, 1.47) and diagnosed at age 75 years or older (adjusted HR, 1.11). Similar results can be seen in AD and VD.
To our knowledge, while current epidemiological studies still focus predominantly on the association between AF and subsequent cognitive decline or incident dementia, the present study is the largest study to explore the association between AF onset age and incident dementia. Based on accurate data on AF diagnoses and incident dementia, the most distinguished finding of our research was that an earlier diagnosis of AF was associated with an elevated risk of developing all-cause dementia, AD, and VD.