However, authors conclude the connection may have more to do with anti-hypertension medication than high blood pressure itself.
"It's likely that this protective effect is coming from antihypertensive drugs," said co-author John Kauwe, associate professor of biology at Brigham Young University. "These drugs are already FDA approved. We need to take a serious look at them for Alzheimer's prevention."
The study, published this month in PLOS Medicine, analyzed genetic data from 17,008 individuals with Alzheimer's and 37,154 people without the disease. Data came from the Alzheimer's Disease Genetics Consortium and the International Genomics of Alzheimer's Project.
BYU researchers worked with scholars from the University of Cambridge, Aarhus University in Denmark and the University of Washington on the massive study. BYU's role was to flex its muscles in supercomputing and bioinformatics. With the help of BYU's supercomputer, Kauwe and undergraduate student Kevin Boehme pieced together 32 data sets for the analysis.
The research team looked for links between Alzheimer's disease and a number of health conditions -- including diabetes, obesity, and high cholesterol -- but only found a significant association between higher systolic blood pressure and reduced Alzheimer's risk. (A weak connection between smoking and Alzheimer's also surfaced.)
"Our results are the opposite of what people might think," said fellow co-author Paul Crane, a University of Washington associate professor of internal medicine. "It may be that high blood pressure is protective, or it may be that something that people with high blood pressure are exposed to more often, such as antihypertensive medication, is protecting them from Alzheimer's disease."
University of Cambridge senior investigator scientist Robert Scott led the study, which used "Mendelian randomization" to find if the risk factors (BMI, insulin resistance, blood pressure, cholesterol, diabetes) for Alzheimer's had a causal impact. Mendelian randomization uses subjects' genetics as a proxy for a randomized clinical trial.
"This is to date the most authoritative paper looking at causal relationships between Alzheimer's disease and these potentially modifiable factors," Kauwe said. "In terms of the number of samples, it can't get bigger at this point."