A study conducted by the Mayo Clinic took in a number of patients in 1998, all of whom were diagnosed with atrial fibrillation. This is a condition that affects the upper chambers of the heart, which often has the effect of causing an erratic, irregular pulse as a primary sign. The problem is generally asymptomatic and only fatal in extreme cases, though palpitations, chest pains, fainting, and congestive heart failure are all possibilities. Atrial fibrillation is only a major concern when it is chronic, wherein it has the potential to be highly fatal. The Mayo Clinic study followed the subjects up to 2006, where they noted a startling similarity between them.
The researchers found that roughly 300 of the patients developed dementia and other behavioral disorders, such as depression. The statistics also showed that those that developed dementia and other mental health disorders had a higher fatality rate because of atrial fibrillation than those who had their minds intact. Age also appeared to have played some sort of role, with the problem appearing in people who were 50 or above, though it was notable that most of them were in good health (aside from the aforementioned circulatory ailment) for their particular age bracket.
The research team is currently unsure of what, exactly, is causing this to occur. The effects of things like depression and insomnia on the heart have been studied in the past, particularly due to the lack of sleep that both things can cause. However, no insomnia or significant sleep disorders were detected by the research team on the test subjects, which has opened room for speculation on what dementia had to do with the increased fatality rate and the presence of the heart ailment. Also, due to the nature of the study and the specific limitations of the research procedures and period, there was no way to determine if the heart ailment was caused by the dementia or if it was the other way around.
The fact that atrial fibrillation is a rather common ailment in contrast to the relative rareness of true dementia does pose some interesting questions. There are several cases of side effects that can worsen the original conditions, so it is possible that dementia is among those factors. However, there is currently no clear idea on how a heart ailment is affecting the brain, especially because there is no indication that atrial fibrillation causes abnormal amounts of blood (whether lessened or increased) to be sent to the brain.