The more risk factors for vascular disease one has in middle age, the higher the risk may be of developing Alzheimer’s disease in later life: the conclusion of a new study published in JAMA.

Vascular disease is defined as any condition that affects the circulatory system–the vessels that carry the blood to and from the heart. Types of vascular disease include atherosclerosis, the hardening or narrowing of the arteries due to plaque buildup, and peripheral artery disease, the narrowing of the arteries in the limbs. Obesity, high cholesterol, high blood pressure, diabetes, and smoking are some of the common risk factors for vascular disease.

Previous studies have suggested a link between vascular disease risk factors during midlife and increased risk of later-life dementia—particularly Alzheimer’s disease—the most common form of dementia.

However, Dr. Rebecca F. Gottesman – of the Department of Neurology at Johns Hopkins University School of Medicine in Baltimore, MD – and colleagues note that it has been unclear as to whether these risk factors are directly associated with the buildup of beta-amyloid in the brain.

Beta-amyloid is a protein associated with the development of Alzheimer’s disease. The protein can accumulate in the brain, forming “plaques” that disrupt communication between nerve cells. With the help of positron emission tomography (PET) brain imaging, Dr. Gottesman and team sought to gain a better understanding of how risk factors for vascular disease might affectbeta-amyloid accumulation in the brain.

The researchers analyzed the data of 346 dementia-free adults who had participated in the Atherosclerosis Risk in Communities (ARIC)-PET Amyloid Imaging Study for almost 25 years. Participants were a mean age of 52 years at the point of study enrollment between 1987 and 1989. At that time, subjects were assessed for the presence of vascular disease risk factors, including high cholesterol, smoking, high body mass index, high blood pressure, and diabetes.

Between 2011 and 2013 – at a mean age of 76 years – participants underwent PET imaging, which revealed the levels of beta-amyloid in their brains. “The availability of imaging biomarkers for brain amyloid allows the study of individuals before the development of dementia and thereby allows consideration of the relative contributions of vascular disease and amyloid to cognition, as well as the contribution of vascular disease to amyloid deposition,” note the researchers.

Compared with participants who had no risk factors for vascular disease at study baseline, those who had two or more risk factors were found to have significantly higher levels of beta-amyloid in their brains. The more vascular risk factors participants had, the higher were their levels of beta-amyloid.

Contrary to previous studies suggesting that the link between vascular disease risk factors and beta-amyloid levels varies by race, the researchers found that race did not influence their findings. Furthermore, the study results did not differ between people with and without the APOE e4 allele, which is a form of the APOE gene associated with an increased risk of Alzheimer’s disease.

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