The brain like all other organs is affected by ageing and the ageing process, in any tissue or organ, has two effects. One is a loss of the maximum level of ability you can achieve. For example, even if Bradley Wiggins had continued to train he would not have been able to improve his world records because the maximum rate at which his heart could beat will decrease from about forty on. The second effect is loss of resilience, the ability to bounce back after an injury or the onset of a disease or when there is a change in environmental temperature, is reduced by the normal ageing process.
The activities of the brain and the mind are usually classified as being either to do with emotion (feeling) or cognition (logical thinking) and it is the latter that is of greater concern because as what is called normal ageing occurs the brain loses some of the ability to carry out activities such as learning, problem solving, quick decision making and remembering. Of these remembering is most widely recognised and talked about and many people worry that memory slips are the early signs of dementia. Memory slips are not a sign that dementia will inevitably develop and listed in the box below are common memory slips that occur frequently and normally: -
The other type of change that is common and obvious is the loss of ability to make decisions quickly, for example if competing in a television or pub quiz, and much is made of the superior ability of young people's decision-making speed. However, speed is only one criterion by which the quality of a decision should be judged. You certainly need quick decision making if you are flying a fighter jet. However not many people need these skills, and of course, computers with artificial intelligence - the robots - are taking over many of the tasks that require rapid decision making and hand/eye coordination.
Furthermore, many decisions do not have such time pressure, decisions about work and social life for example, and it is possible to make such decisions too quickly. Oscar Wilde wrote that "experience is the name we give to our mistakes" and the importance of experience is now recognised. Older people have more experience and are certainly no worse at making decisions that matter than young people and may even be better because they don't make decisions so quickly, having made so many wrong decisions before.
And the American College of Physicians, a highly respected and scientific organization, emphasised in their report on ageing that although "some cognitive functions, such as memory and reaction time, decrease others such as wisdom and knowledge, increase with age".
So, dementia is a condition that is different from normal ageing. It may be caused by a number of disorders, one of which, Alzheimer's disease, has no known cause and therefore no means of prevention. The importance of dementia is that it makes it difficult to live on your own and it is, therefore, the single commonest cause of disability.