Stroke is the leading cause of disability worldwide and the second leading cause of death. Large and small strokes and disease of small cerebral blood vessels can lead to dementia, as well as milder degrees of cognitive deficit (vascular cognitive impairment). Strokes may be large or small and may occur with or without bleeding in the brain. The brain can also be damaged by a long-term lack of sufficient blood flow with loss of the axons, needed for neurons to communicate with each other. Attention to the four reserve factors (cognitive, physical, psychological, and social) can help to prevent stroke as well as improve recovery and diminish the effect of stroke on cognitive function. Cerebrovascular disease makes a very important contribution to cognitive impairment with aging. Recent studies have demonstrated several ways in which bacteria that reside in the mouth are involved in causing strokes. There are many modifiable risk factors for stroke including a high-fat diet, obesity, smoking, poor oral hygiene, physical inactivity, atrial fibrillation, alcoholism. Lifestyle factors play a large role in the risk of all forms of stroke

The neurodegenerative diseases Alzheimer’s, Parkinson’s, frontotemporal lobar degeneration, Lewy body disease, and amyotrophic lateral sclerosis are all age-related and caused by genes in only 1-10 percent of cases. Dementia describes a syndrome in which there are cognitive difficulties including impaired memory, judgment, planning, language, and other deficits. Alzheimer’s is the commonest cause of dementia. In the brain in neurodegenerative diseases there is abnormal folding of proteins creating thread-like filaments called amyloid. There is also abnormal activation of inflammation with free radicals and harmful cells. There are things we can do regarding diet and other actions that can lower the risk of developing neurodegenerative diseases with aging. High levels of physical and mental activity throughout life along with attention to a healthy plant-based diet can enhance our four reserves and diminish amyloid deposition and overactivity of the immune system. Lifestyle measures can also protect us from the effect of brain pathologies that may develop. There are many causes of memory loss other than Alzheimer’s disease which are completely reversible when properly recognized.

Humans are social beings and relationships with family and friends are critical for health at all stages of life. Studies have shown a higher risk of dementia in later life in individuals with poor social interactions. At all stages of life, it’s desirable for people to have healthy relationships with others. Maintaining a socially active lifestyle in later life enhances cognitive reserve and benefits cognitive function. The physical component of social interactions is also of value. Interpersonal experiences can influence the structure and function of the brain in both early and later life. Opportunities for interactions with other people enhances social reserve and improves cognitive, physical, and psychological reserves. Studies suggests that dementia is more common in those whose social engagement declines from mid- to late-life. Having stronger social contacts protects people from the manifestations of aging and age-related brain disease. Social interactions can be enhanced in aging through community organizations, social action groups, religious activities, and travel. Pursuing activities that help you find meaning will also help you make social connections.

There are several other important causes of dementia in younger and older persons. Normal pressure hydrocephalus is a condition with altered absorption of spinal fluid leading to cognitive losses, gait disturbances, and poor control of urination. It may be successfully treated with surgery. Creutzfeldt-Jakob disease is a rapidly fatal progressive condition caused by a potentially transmissible form of a prion, an abnormally folded protein. Bovine spongiform encephalopathy is another prion disease associated with eating infected cows. It is now recognized that small and large head injuries are bad for the brain and can cause serious cognitive and motor deficits, and progressive untreatable dementia. Repeated blows without visible immediate effect can lead to brain degeneration. A critical way to maintain cognitive reserve is to avoid all kinds of blows to the head. Excess consumption of alcohol is very damaging to brain function and can lead to dementia, as well as nerve damage and injury to several other parts of the body, such as the liver, heart and intestines. It is recommended that men should not consume more than two doses of alcohol a day and women not more than one.

Our ancestors had a vastly different diet than the one we have today. They had a much higher fiber content in their diet with less meat. This earlier human diet led to greater diversity of gut bacteria, which we now understand is important for health. Considerable research is being done worldwide about which bacterial populations will be best to consume as probiotics (live bacteria believed to aid health and enhance bacterial populations in the gut). Consumption of yogurt which has live bacteria is desirable, but don’t eat yogurt with a lot of sugar. Rather than eating yogurt with added fruit and sugar, it’s better to eat plain yogurt and add your own fruit. Prebiotics are non-digestible fibers that cannot be digested by people, which are designed for their ability to be metabolized by desirable gut bacteria. Consumption of high-fiber foods (including fruits, nuts, legumes, brown rice, beans, whole grains, vegetables, whole wheat bread) will have a similar effect on the microbiome as prebiotics. It is wise to avoid low-fiber foods such as red meat, which is high in saturated fat and provides little of the nutrition which is needed by our microbiota.

During stressful experiences the endocrine and brain systems involved have distinct neurochemical processes which enhance the power of the memory. Post-traumatic stress disorder is due not only to psychological factors, but neurochemical and evolutionary ones as well. It is valuable for people who have experienced stressful life events to realize that the power these memories have is not entirely psychological. It is in a deeply developed neural pathway created and preserved in the brain in a resilient fashion. Understanding that this is not a question primarily of “getting over It,” but rather “learning to live with it” may help. Stress has many effects on the brain and the body. Bolstering your physical reserves with physical activity, effective sleep, and a healthy diet enhances the ability to deal with stress. The experience of stress involves not only the brain, but also the body’s cardiovascular system and other parts. It is best if the work of dealing with stressful factors is accomplished early, before the achlyievement of great age. Several strategies can help to deal with stress: restful sleep, meditation, diet, cognitive and physical exercise, and avoidance of toxins.

Humans are born with 23 pairs of chromosomes and 20,000-25,000 genes. Genes are sequences of nucleotides (the basic structural unit of nucleic acids) that code for the amino acid sequence of proteins. It is important to know that the genetic information contained in the chromosomes does not directly determine what happens to us. Rather, the genes provide information about what can be done. What actually happens is an interaction between the genes and the environment. That is, how we live influences the action of our genes - the context is supreme. Genes are the cause of Alzheimer’s in only 1 percent of cases. A form of the apolipoprotein E gene called e4 increases the risk of getting Alzheimer’s by 2-10 times, depending on the dose of the gene (one or two copies). However, many persons with the risk form of the gene are not affected. In the majority of cases of Alzheimer’s there is a key interaction of genes and environmental factors which determines who becomes affected and at what age. Although genetic testing can be done to predict risk it is not currently recommended, as genetic tests are not needed to have commitment to preventive measures.

The mouth is home to more than 1,000 different species of microbes. These microbes live in the nose, mouth and throat and help to protect us against invasive disease-causing organisms. We don’t have a choice about their residency in our bodies. If we wanted to remove them once and for all we would need a blow torch. That is to say, they can’t be removed. Because of their contribution to disease, we must monitor and control their populations as best we can. To put it another way: we need them, and they need us. We must be sure that they are not having a party in our mouth. The best way to avoid having an unhealthy population of organisms is to practice good oral hygiene: brush upon wakening, after meals and at bedtime, use dental floss, and visit a dentist two or three times a year for check-ups and cleaning.We need to take care of our oral health because it is good for our brain and heart. Of course, it’s also good for our teeth, but consideration of the role of oral health in brain and heart disease will help us to understand its importance to our health and fitness.

Depression is common in older people and people who are depressed may have significant memory problems. Recurrent thoughts of sadness may interfere with the registration of new memories. It can develop as a response to life events and appear independently of what is happening. People with a history of serious depression may experience more depression with age. However, people who didn’t experience depression in their younger years may also develop depression. Depression may be a warning sign of mental or physical illness, or a sign of a troubled relationship. Many depressed older persons are aware of their depression, but some are not. Recognizing the presence of depression is key to dealing with it effectively. Signs of depression include sadness and recurring thoughts of regret. Depression is also indicated by loss of appetite, loss of weight, difficulty with sleeping, and loss of interest in activities. There is a vicious cycle in which lack of activity leads to depression, which leads to a lack of activity. Also, social media can also induce negative emotional states. The ability to manage our response to life events is a fundamental part of psychological reserve.

Understanding of the magnificence and uniqueness of the brain is important for realizing the goals of aging. We must respect its central role in our lives and work to see what we must do to enhance its health throughout life. The brain is precisely responsive to activities and its structure is changed by learning. It is also uniquely sensitive to damage and has a limited capacity for repair, compared to other body parts. What we do changes the brain, and the nature of our mental activities modifies the ability of the brain to resist declines with aging and disease. Cognitive involvement in educational, occupational, and recreational tasks throughout life, as well as physical activities, helps to enhance resistance to decline with age and diseases such as Alzheimer’s. This chapter examines how the four reserves (cognitive, physical, psychological, and social) help to maintain brain function with age. Recent research has uncovered the influence of our partner microbes in the gut on learning, memory, and age-related diseases of the brain. These developments beautifully illustrate how there are things we can all do to maintain brain function with age.

A critical component of the theory of the multiple reserves is that the health of the body is good for the health of the brain. The brain is dependent on all other body parts for maintenance of its functions. This dependence upon other bodily functions is especially prominent in older persons, because of their lower reserve capacities. Research has shown that intensive blood pressure control is more effective than standard blood pressure control in reducing the risk of cognitive impairment. It is certainly true that "what is good for the heart is good for the brain.” It is valuable to have the best possible heart, lung, kidney, liver, and endocrine function. Diabetes increases the risk of Alzheimer’s disease as well as small and large strokes. Avoidance of obesity and physical exercise can lower the risk of diabetes. A high-fiber diet can improve insulin responsiveness and diminish the severity of diabetes. The recommendations in this book are good for the health of the heart, lungs and other organs as well as directly beneficial to the nervous system. Good systemic health means good physical reserve. Good physical reserve helps to maintain healthy brain function throughout life.