The average life expectancy is at its highest ever in history. Brain cells are built to live up to 127 years. However, they do not divide and replicate the same way other cells do, and so their vulnerability to attack by radiation and free radicals is more problematic. Cell loss in the normal ageing brain is patchy. There is a small stock of stem cells from which neuronal regeneration is possible, but scientists are still only just learning of their full functions now. It is believed that the brain shrinks with age. Amongst European populations it can shrink by as much as 15% between the ages of fifty and sixty-five. Much of this reduction is due to brain cells shrinking as they lose water, while the spaces in the brain (called ventricles) and the folds of the cortex (called sulci) enlarge. Blood supply also diminishes slightly with age.
Of greatest importance are the connections between nerve cells. It is these connections that must constantly battle for survival. The gift of prolonged life is not without its anxieties. We worry about losing our memory and about the reduction in our cognitive performance. While there is an increase in the range and complexity of our language, this is accompanied by an increased frequency of mistakes, forgetting words or misnaming objects. We should remind ourselves that with age, there are greater powers of reflection and contemplation. The wonderful gift of experience is to be rejoiced. The aging brain has a greater capacity to deal with complex emotions and to complement decisions with a raft of knowledge. While the ageing brain is slower, it is this slowness in decision-making that allows time for better decisions to be made—this is called wisdom.