Alzheimer's disease is a non-reversible brain disorder that usually begins after the age of 65, and currently affects as many as five million Americans. In a recent study, scientists discovered — in cognitively normal older adults with no symptoms of the disease — a relationship between pulse pressure (PP) and biomarkers for Alzheimer’s disease found in their cerebrospinal fluid (CSF).

“These results suggest that the forces involved in blood circulation may be related to the development of the hallmark Alzheimer's disease signs that cause loss of brain cells," author Daniel A. Nation, PhD, of the VA San Diego Healthcare System, stated in a press release.

Pulse Pressure and Biomarkers

The study involved 177 participants between the ages of 55 and 100. None of the participants showed any symptoms of Alzheimer’s disease (AD). After having their pulse pressure taken, they underwent lumbar punctures to obtain spinal fluid. Pulse pressure, which is the top number in a blood pressure reading, is also known as systolic pressure, and is an index of the aging of the vascular system. Generally, systolic pressure gradually increases with age, beginning around 30. This increase is due to a worsening stiffness of the large arteries of the body, particularly the aorta (The largest artery, which first receives blood pumped out of the heart.) and its tributaries.

Surprisingly, the study found that people who have higher pulse pressure readings were more likely to have the Alzheimer’s biomarkers amyloid beta (plaques) and p-tau protein (tangles) in their cerebral spinal fluid than those with lower pulse pressure readings. In fact, for every 10 point rise in pulse pressure, the average level of p-tau protein in the spinal fluid rose by 1.5 picograms per millileter. Significantly, this connection between biomarker and pulse pressure was discovered in participants between the ages of 55 and 70, but not in people older than 70.

“This is consistent with findings indicating that high blood pressure in middle age is a better predictor of later problems with memory and thinking skills, and loss of brain cells than high blood pressure in old age,” Nation said in the press release.

Alzheimer’s Biomarkers and Three Major Hallmarks

Alzheimer's disease is one of a group of disorders called “dementias,” each of which is characterized by cognitive decline and, often, behavioral problems. Among people over the age of 65, AD is the most common cause of dementia. Someone who is succumbing to the disease will experience memory loss and confusion, but unfortunately, family and friends often mistake these symptoms for the usual memory deficits that occur during normal aging. However, AD is not normal and eventually leads to harsh realities, including the inability to recognize family and friends, a decline in cognitive abilities (particularly in the area of language skills), and behavior and personality changes. Ultimately AD includes a shocking loss of mental function. Through post-mortem analyses, scientists have discovered three major hallmarks identified with AD:

  1. Amyloid plaques are made up of fragments of a protein called beta-amyloid peptide mixed with a other proteins, remnants of neurons, and bits and pieces of other nerve cells. Scientists have discovered an unusual buildup of this plaque in the brains of people suffering from AD.
  2. Neurofibrillary tangles (NFTs), which are contained within neurons (brain cells), are abnormal collections of a protein called tau. Although tau is necessary for the health and function of neurons, in AD, tau clumps together and hinders neurons from functioning normally so that eventually they die.
  3. Loss of connections between neurons responsible for memory and learning is the third and final hallmark of AD. Neurons, like people, don’t survive very long once they lose their connections to other neurons. As neurons begin to die throughout the brain, whole regions atrophy, damage becomes widespread, and soon, the entire mass of brain tissue has shrunk significantly.

The above study linking pulse pressure to biomarkers of Alzheimer's disease is significant because so many people are hoping scientists soon discover a reliable, early warning indicator of the disease. Some argue that early knowledge is essentially useless since there is still no cure for Alzheimer's disease. Others believe early warning would, at the very least, give scientists more knowledge of the disease and a longer time to study the illness, and both of these possibilties would aid them in developing therapies to stop or slow the course of the disease.

Source: Nation DA, Edland SD, Bondi MW, et al. Pulse pressure is associated with Alzheimer biomarkers in cognitively normal older adults. Neurology. 2013.