Here I'll point out two papers, one looking at exercise and the aging of grey matter in the brain, the other looking at exercise and the aging of white matter in the brain. It is well known that cardiovascular health is linked to cognitive health. An entire category of neurodegenerative disease is related to the age-related failure of the cardiovascular system to remain intact and supply adequate nutrients to the brain. A sizable portion of cognitive decline is linked to incidences of rupture of tiny blood vessels in the brain, each killing a comparatively small number of cells, but over the years that damage adds up. Further, the cellular biochemistry of the brain is kept separate from the body by the blood brain barrier, a layer of cells that lines the blood vessels of the brain. As blood vessels age, that barrier breaks down, allowing molecules present in the rest of the body to leak into the brain, producing disruption and damage. All in all, the quality of blood vessels matters greatly, just as much as the ability of the heart to pump enough blood to the energy-hungry brain. Scores of studies provide evidence to support a strong link between the cardiovascular system and the brain, with data at every layer of scientific investigation, from epidemiology to physiology to cellular biochemistry.
Since true, actual, working rejuvenation therapies are still very new and limited in scope, the way in which researchers presently observe the effects of cardiovascular health on the aging of the brain is by comparing people with different levels of fitness. Exercise modestly slows the pace at which the corrosive damage of aging harms the function and integrity of the vascular system and the heart, though animal studies suggest that exercise, while beneficial for long-term health, doesn't greatly extend life span. A sizable fraction of declines in measures of cardiovascular function across the middle of life results from a reduction in exercise rather than the intrinsic processes of damage that come to dominate the progression of aging in late life. Yet even in late life, undertaking physical exercise is beneficial - the cell and tissue damage of aging may be the dominant factor in reduced health and increased dysfunction, but exercise still helps to a degree that makes it worth the effort.
Ultimately, we should look at the data from the two studies noted here, and from the many other similar studies carried out over the years, and think: "if a modest positive impact on the biochemistry of the vascular system has this effect, how much better would it be to repair the underlying damage that causes aging?" The decline of the physical structure of the brain - and the mind it supports - will one day be prevented through the advent of rejuvenation therapies after the SENS model: repairing the root causes of aging, the cell and tissue damage that results in loss of function and catastrophic failure of organs and other systems in the body. A world absent aging is something to strive for, and the differences in aging of individuals that we observe today are just a tiny fraction of what will become possible through new medical science in the years ahead.
A new study from suggests that the lower the fitness level, the faster the deterioration of vital nerve fibers in the brain. This deterioration results in cognitive decline, including memory issues characteristic of dementia patients. The study published focused on a type of brain tissue called white matter, which is comprised of millions of bundles of nerve fibers used by neurons to communicate across the brain. Researchers enrolled older patients at high risk to develop Alzheimer's disease who have early signs of memory loss, or mild cognitive impairment (MCI). The researchers determined that lower fitness levels were associated with weaker white matter, which in turn correlated with lower brain function.
Unlike previous studies that relied on study participants to assess their own fitness, the new research objectively measured cardiorespiratory fitness with a scientific formula called maximal oxygen uptake. Scientists also used brain imaging to measure the functionality of each patient's white matter. Patients were then given memory and other cognitive tests to measure brain function, allowing scientists to establish strong correlations between exercise, brain health, and cognition.
The study leaves plenty of unanswered questions about how fitness and Alzheimer's disease are intertwined. For instance, what fitness level is needed to notably reduce the risk of dementia? Is it too late to intervene when patients begin showing symptoms? Some of these topics are already being researched through a five-year national clinical trial. The trial, which includes six medical centers across the country, aims to determine whether regular aerobic exercise and taking specific medications to reduce high blood pressure and cholesterol levels can help preserve brain function. It involves more than 600 older adults at high risk to develop Alzheimer's disease.
The gray matter in the brain includes regions responsible for controlling muscle movement, experiencing the senses, thinking and feeling, memory and speech and more. The volume of gray matter is a measure of brain health, but the amount of gray matter in the brain often begins to decrease in late adulthood, even before symptoms of cognitive dysfunction appear. "More gray matter is associated with better cognitive function, while decreases in gray matter are associated with Alzheimer's disease and other related dementias."
The study measured the levels of physical activity by 262 older adults in the Memory and Aging Project, an ongoing epidemiological cohort study. Participants in the lifestyle study wore a noninvasive device called an accelerometer continuously for seven to 10 days. The goal was to accurately measure the frequency, duration, and intensity of a participant's activities over that time. The use of accelerometers was only one of the ways in which this analysis differed from some other investigations of the health of older people. Most research that explores the effects of exercise relies on questionnaires. The real problem with questionnaires, though, is that "sometimes, we get really inaccurate reports of activity."
Another departure from some other investigations was the opportunity to assess the effects of exercise on individuals older than 80. In fact, the mean age in this study was 81 years, compared with 70 for other studies used as a reference. The study compared gray matter volumes as seen in participants' MRIs with readings from the accelerometers and other data, which all were obtained during the same year. Analysis found the association between participants' actual physical activity and gray matter volumes remained after further controlling for age, gender, education levels, body mass index and symptoms of depression, all of which are associated with lower levels of gray matter in the brain.