Vascular aging is an important contribution to neurodegeneration. The brain is an energy-hungry organ, and reductions in blood flow with age have a negative impact on brain tissue. These reductions can occur for obvious reasons such as the weakening of the heart in cases of heart failure, but there are other, more subtle processes at work to reduce the delivery of nutrients to the brain, such as the progressive stiffening of blood vessels and reductions in capillary density. Researchers here note that greater excess fat tissue, as measured by body mass index, correlates with reduced blood flow in the brain. It is plausible that this is mediated by the higher levels of chronic inflammation generated in people with larger than needed visceral fat deposits, as inflammation accelerates dysfunction in the vascular system, as well as dysfunction in tissue maintenance in general.
As a person's weight goes up, all regions of the brain go down in activity and blood flow, according to a new brain imaging study. One of the largest studies linking obesity with brain dysfunction, scientists analyzed over 35,000 functional neuroimaging scans using single-photon emission computerized tomography from more than 17,000 individuals to measure blood flow and brain activity. Low cerebral blood flow is the primary brain imaging predictor that a person will develop Alzheimer's disease. It is also associated with depression, ADHD, bipolar disorder, schizophrenia, traumatic brain injury, addiction, suicide, and other conditions.
Striking patterns of progressively reduced blood flow were found in virtually all regions of the brain across categories of underweight, normal weight, overweight, obesity, and morbid obesity. These were noted while participants were in a resting state as well as while performing a concentration task. In particular, brain areas noted to be vulnerable to Alzheimer's disease, the temporal and parietal lobes, hippocampus, posterior cingulate gyrus, and precuneus, were found to have reduced blood flow along the spectrum of weight classification from normal weight to overweight, obese, and morbidly obese.