Low Cardiac Index May Be an Important Risk Factor for Alzheimer’s Disease

A recent study revealed that heart function is an important risk factor in the development of dementia and Alzheimer’s disease. The study entitled “Low Cardiac Index is Associated with Incident Dementia and Alzheimer’s Disease: The Framingham Heart Study” was published in Circulation by Dr. Angela L. Jefferson from Vanderbilt Memory & Alzheimer’s Center, Nashville, TN, USA, and colleagues.

The number of patients with dementia is estimated to be 44 million worldwide and is expected to reach 76 million people in 2030. More than half of dementia patients suffer from Alzheimer’s disease and the numbers are moving in an upward trend. Cross-sectional epidemiological and clinical studies have been suggesting an association between lower cardiac index and abnormal brain aging, including smaller brain volumes, increased white matter hyperintensities, and worse cognitive performances. Lower systemic blood flow may have implications for dementia among older adults.

The research team analyzed data from the Framingham Heart Study, a research project that began in 1948 with the aim of identifying risk factors for heart disease. In this study, 1,039 participants from Framingham’s Offspring Cohort were followed for 11 years to compare cardiac index to the development of dementia. The cardiac index parameter is a measurement of heart function by calculating the quantity of blood that is pumped out of the heart to the all body when considering individual body size. A low cardiac index value means less blood being pumped from the heart. The researchers found that participants with decreased heart function, measured by cardiac index, were 2 to 3 times more likely to develop significant memory loss during the follow-up period. During the study, 32 participants developed dementia, including 26 cases of Alzheimer’s disease. Importantly, individuals with clinically low cardiac index had a higher relative risk of dementia.

Dr. Angela Jefferson, principal investigator of the study, said in the news release that heart function may be an important risk factor for dementia and Alzheimer’s disease.

Dr. Jefferson said that this finding is encouraging since heart health is a risk that can be modified contrary to genetics or family history. She added that an individual can change his heart healthy lifestyle through diet and exercise at any point in his life. Researchers for a long time have associated heart health with brain health, while the cardiac index never was until now accepted as a risk factor for significant memory loss or dementia.

She also explained that normally the brain of an adult individual corresponds to 2% of overall body weight but gets as much as 15% of blood pumped from the heart. When there are alterations in the capability of the heart to pump blood, the brain has the ability to regulate blood flow and maintain a constant level from brain tissue and activity. She added that when this happens, the vessels are less adaptable to changes in blood flow, affecting brain health and function.

“The risk we found between lower cardiac index and the development of dementia may reflect a subtle but protracted process that occurs over decades — essentially a lifetime burden of subtle reductions in oxygen and nutrient delivery to the brain,” added Jefferson.

Dr. Jefferson concluded saying that currently there is no method to prevent dementia or Alzheimer’s disease development, but having a healthy lifestyle will surely help. Since 30% of the general population is exposed to a low cardiac index potential risk factor, this may be seen as an important public health issue.