The quality of the vasculature is an important determinant of the pace of aging in the brain. There are probably several distinct processes involved, all of which tend to correlate with one another as aging progresses. Firstly the brain is an energy-hungry organ, but the network of tiny capillaries in tissues becomes less dense with age. A consequently lower supply of nutrients to cells causes loss of function. The same result may also occur due to the age-related weakening of the muscles of the heart. Secondly, blood vessels lose their elasticity in later life, and this in turn causes a rise in blood pressure as feedback mechanisms run awry. Higher blood pressure causes damage to sensitive tissues in many organs through a variety of means, such as a greater rate of rupture or blockage of tiny blood vessels. The brain of an older individual is riddled with the minuscule scars left by these events, and that damage adds up.
Why do blood vessels grow stiff with age? A mix of underlying causes, not all of which are fully understood. Persistent cross-links that our biochemistry cannot break down glue together structural proteins of the extracellular matrix, altering the structural properties of tissue. Rising inflammation and signals from senescent cells contribute to both calcification of blood vessel walls and dysfunction in the smooth muscle cells responsible for contraction and dilation. The behavior of smooth muscle is more responsive to lifestyle circumstances than other factors; better diet, avoiding excess fat tissue, and greater fitness are thought to have an impact, either through reduced inflammation and or other mechanisms, whereas there isn’t much that can be done about existing calcification or cross-linking given the tools to hand today.
Greater fitness and better lifestyle choices only slow the progression of aging to some degree – and only meaningfully impact a fraction of its mechanisms. But in an era of rapid progress in medical biotechnology, in which the research community is finally waking to the potential of treating aging and its causes, it makes sense to adopt lifestyle choices that reliably help long-term health, even if the outcome at the end of the day is just a few years gained. Those few years may make a sizable difference, between on the one hand living long enough and in good enough health to benefit from future technologies of rejuvenation, and on the other hand missing that boat.
The rate of decline in certain aspects of memory may be explained by a combination of overall physical fitness and the stiffness of the central arteries, researchers have found. “Exactly why this occurs is unclear, but research indicates that exercise and physical fitness are protective. A healthier, more elastic aorta is also theorised to protect cognitive function, by reducing the negative effects of excessive blood pressure on the brain.”
One hundred and two people (73 females and 29 males), aged between 60 and 90 years, living independently in aged care communities, were recruited. Their fitness was assessed with the Six-Minute Walk test which involved participants walking back and forth between two markers placed 10 metres apart for six minutes. Only participants who completed the full six minutes were included in the analysis, which assessed the stiffness of their arteries and cognitive performance. The researchers found that (along with Body Mass Index and sex) the combination of fitness and aortic stiffness explained a third of the variation in performance in working memory in older people.
Interestingly, physical fitness did not seem to affect central arterial stiffness, however only current fitness was assessed – long term fitness may be a better predictor of central arterial stiffness, however this has yet to be investigated. “Unfortunately, there is currently no effective pharmacological intervention that has proven effective in the long term in staving off dementia. The results of this study indicate that remaining as physically fit as possible, and monitoring central arterial health, may well be an important, cost effective way to maintain our memory and other brain functions in older age.”
Greater physical fitness is associated with reduced rates of cognitive decline in older people; however, the mechanisms by which this occurs are still unclear. One potential mechanism is aortic stiffness, with increased stiffness resulting in higher pulsatile pressures reaching the brain and possibly causing progressive micro-damage. There is limited evidence that those who regularly exercise may have lower aortic stiffness. Our objective is to investigate whether greater fitness and lower aortic stiffness predict better cognitive performance in older people and, if so, whether aortic stiffness mediates the relationship between fitness and cognition.
Residents of independent living facilities, aged 60-90, participated in the study (N = 102). Primary measures included a computerized cognitive assessment battery, pulse wave velocity analysis to measure aortic stiffness, and the Six-Minute Walk test to assess fitness. Based on hierarchical regression analyses, structural equation modelling was used to test the mediation hypothesis. Both fitness and aortic stiffness independently predicted Spatial Working Memory (SWM) performance, however no mediating relationship was found. Additionally, the derived structural equation model shows that, in conjunction with BMI and sex, fitness and aortic stiffness explain 33% of the overall variation in SWM, with age no longer directly predicting any variation.
Thus greater fitness and lower aortic stiffness both independently predict better SWM in older people. The strong effect of age on cognitive performance is totally mediated by fitness and aortic stiffness. This suggests that addressing both physical fitness and aortic stiffness may be important to reduce the rate of age associated cognitive decline.