One of the greatest current challenges in medical science is to understand the ageing process in sufficient detail to allow us to open new paths to improving the quality of the later years of life. It is important to be clear that the goal is to improve the quality of life in old age rather than to extend the length of life regardless of its quality. All of us, if we live long enough, will experience aspects of ageing that will increase our frailty and limit our independence but we do not all age in the same way. Some will remain free from disease for a very long time, whereas others will develop one or more of a range of age-related diseases.

What is normal ageing and how is it related to the diseases of old age? Do different diseases share common causative mechanisms?

Can these diseases be slowed or prevented by changes in nutrition or lifestyle, as well as by medical drugs?

What is ageing and why does it occur?

In one sense we all know what ageing is, although scientifically the mechanisms have been very hard to pin down. We used to think that ageing was programmed into us by some kind of death clock, but this view is no longer widely held. We now think that ageing happens because during our lifetime the cells and tissues of our bodies accumulate many microscopic faults that eventually get in the way of normal functions. The good news is that if we can find ways to reduce this damage, or to increase the effectiveness of our natural repair systems, we might delay the onset of disease.

Cell ageing.

Human cells from normal tissue can be propagated in the test tube, but eventually they stop growing, age and die. Cells grown from old donors divide less than cells from young donors, so there is good reason to believe that the study of cell ageing can throw light on the ageing of the body as a whole. Research is identifying some of the factors that appear to control cell ageing. The cells that make up the organs of the body (e.g. brain, skin, bone) age in different ways and at different rates. However, all cells have to cope with similar kinds of damage, and common factors may affect their ageing. Understanding the role of common factors in the development of different age-related diseases is a unique benefit that comes from studying the cellular basis of ageing. Work funded by Research into Ageing is examining how cells age. The kinds of damage most likely to cause ageing are in the genetic material (DNA) of cells and the accumulation of altered cellular components. Altered proteins are important in diseases as diverse as Alzheimer's disease and cataracts, while mutations play a part in cancers (many of which become commoner with age), and in muscle weakness. Much of the damage arises as a by-product of normal living. For example, 1-2% of the oxygen we breathe gives rise to highly reactive molecules called free radicals which can damage DNA and proteins. Our bodies have excellent natural protection against mutations and free radicals, which is why we live as long as we do, but some faults slip through.

The role of genetics

Genetic research is providing valuable clues to ageing and age-related diseases. The fruit fly and soil nematode worm are helping to identify genes that affect life span. Many of these turn out to be genes that control maintenance and repair systems. In humans, genes are being found that affect the risk of age-related diseases such as Alzheimer's disease and osteoarthritis.

Nutrition and lifestyle

Current understanding of the ageing process places a priority on good nutrition, because food fuels the natural repair systems and provides the raw materials for healthy cell turnover. Low calorie intake in some animals has been shown to improve health in old age, but it is not known whether calorie restriction has the same effect in humans. Exercise has clear benefits for health, as long as precautions are taken to avoid injury. Recent work has shown that regular exercise can slow the development of age-related decline in muscle.

The need for further research

Although much is known about the ageing process, we lack a detailed knowledge of the precise mechanisms and how these contribute to age-associated disease. Basic ageing research is a relatively new field. Not only do we still need answers to these fundamental questions, but we also need to train dedicated young researchers. Our goal is a deeper understanding of the mechanisms responsible for infirmity and disease in old age, which can be used to enhance and extend quality of life. The scale of the task is immense.