Researchers here explore the age-related nature of the correlation between atrial fibrillation and dementia risk. The earlier that atrial fibrillation is diagnosed in life, the higher the increased risk of later dementia. The interesting question is which of the possible mechanisms are most important in driving this relationship. The nature of atrial fibrillation suggests that both it and dementia arise from the same underlying causes, and that the atrial fibrillation is an earlier sign of those causes. It is associated with excess weight and hypertension, for example, both of which are harmful to the brain over the long term.
In a new study, the researchers assessed the independent association between atrial fibrillation (AF) and incident dementia in Catalonia, Spain. The population-based observational study included individuals who, in 2007, were at least 45 years old and had no prior diagnosis of dementia. The study included 2,520,839 individuals with an average follow-up of 13 years. At baseline, 79,820 patients (3.25%) had a recorded diagnosis of AF. In multivariable analyses adjusting for potential confounders, AF was, overall, a statistically significant but weak predictor of dementia, linked with a 4% increased risk of dementia.
However, age was found to significantly affect the association between AF and dementia. In prespecified analyses stratified by age, the strength of the association progressively weakened with increasing age: in patients aged 45-50, those with AF were 3.3 times more likely to develop dementia than those without AF. But in patients aged over 70 years, no association was found. Further analysis shows the association lost statistical significance from 70 years. By contrast, in patients diagnosed with AF before the age of 70, the condition independently increased the risk of dementia by 21%, and an even stronger effect was observed for early-onset dementia diagnosed prior to age 65, with AF increasing the risk by 36%.
Sensitivity analyses that removed cases of previous stroke during follow-up yielded similar results: AF was associated with a modest increase (6%) in the risk of dementia in the overall population, a stronger association (23% increased risk) in those diagnosed with AF in midlife (younger than 70 years old) and had the greatest effect towards early-onset dementia (52% increased risk). Therefore, patients with AF without a prior stroke still have a higher risk of dementia, with the greatest risk observed in early-onset dementia.
"The observation that the association between AF and dementia remains unchanged after excluding patients with prior stroke indicates that other mechanisms must be involved in the increased risk of dementia among AF patients. These mechanisms may include silent strokes - meaning those that showed no clinical symptoms and can only diagnosed with CT scan or MRI - and also microinfarcts, and microbleeds. Haemodynamic changes, which involve alterations in the flow and pressure of blood in the body caused by AF, and autonomic dysregulation, which refers to an imbalance in how the body controls automatic functions like heart rate, breathing, or blood pressure, could also play a role in the disease of small blood vessels in the brain associated with dementia. Additionally, systemic inflammation associated with atrial fibrillation may amplify these effects, creating a synergistic pathway that further increases dementia risk."
Link: https://www.eurekale...eleases/1078453
View the full article at FightAging
