June 3, 2014
Mentally alert men and women who have signs of high blood pressure in middle age are more likely to have brain changes that may point to memory problems and Alzheimer’s disease in old age, a new study suggests.
For the study, published in Neurology, from the American Academy of Neurology, researchers measured a blood pressure reading known as pulse pressure. Pulse pressure is derived from taking the top number in a blood pressure reading (the systolic pressure) and subtracting the bottom number (or diastolic pressure). Someone with a blood pressure reading of 120/80, for example, would have a pulse pressure of 40.
Pulse pressure tends to increase with age, a result of aging and diminishing function of blood vessels. Hardening of the arteries and other problems can all contribute to increases in pulse pressure.
For the study, researchers at the VA San Diego Healthcare System examined 177 people, ages 55 to 100. None had serious memory loss or other symptoms of Alzheimer’s disease. Pulse pressure was measured in the study participants. Samples of their spinal fluid, which bathes the brain, were also obtained to look for markers of Alzheimer’s, including beta-amyloid and tau, two proteins that signal an increased risk of the disease.
The researchers found that for people in their 50s and 60s, those who had higher pulse pressure were more likely to have higher levels of toxic beta-amyloid and tau. These findings persisted even after the authors controlled for other dementia risk factors, including age, weight and the presence of the APOE-E4 gene, which raises Alzheimer’s risk. This link did not apply, though, for those over 70, perhaps because in the elderly other risk factors take on a more important role.
“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,” said study author Daniel A. Nation. “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.”
Previous research has noted a link between high blood pressure and later Alzheimer’s disease. The results of this study suggest that high blood pressure may cause changes typical not just of dementia in general but of Alzheimer’s disease in particular, including an increase in levels of beta-amyloid and tau.
Other studies have shown that adults with untreated high blood pressure who also have a family history of Alzheimer’s were at particularly high risk of beta-amyloid buildup. Adults who were taking blood pressure medicines, even those with genetic risks for Alzheimer’s, on the other hand, had levels of plaque buildup that were equivalent to those who did not have high blood pressure or a genetic risk.
More research is needed to better understand the link between high blood pressure and Alzheimer’s, but a growing body of evidence shows that keeping blood pressure in check is good for the brain. It may even help stave off Alzheimer’s disease years down the road.
Source: Daniel A. Nation, PhD, Steven D. Edland, PhD, Mark W. Bondi, PhD, et al: “Pulse Pressure Is Associated With Alzheimer Biomarkers in Cognitively Normal Older Adults.” Neurology, Nov. 13, 2013.