Aging is a process that can affect almost all the systems in the body. With increasing age, physically and mentally healthy adults gradually become less fit and become more vulnerable to illness and death. However, these changes happen at different rates in different people.

Scientists are looking for a more complete understanding of the mechanisms of aging, to answer questions about the biological processes that account for an inevitable decline in physical vitality. For example, is there an underlying process that accounts for grey hair, wrinkled skin, decreased muscle strength, increased susceptibility to disease, and all the other consequences of aging?

In other words, is aging a single process with several different results or are separate processes going on in different body systems, such as the immune system, the bones, the muscles, etc. Some researchers have suggested that oxidative damage may be an underlying cause of aging. Over the course of a lifetime, free radicals in the body may do damage to tissues in different parts of the body that eventually causes the effects of aging. This is still only a theory, among several.

More and more research is being conducted into the process of aging and ways in which the process can be slowed. In order to test new interventions (whether they be drugs, vitamins, or other techniques), there has to be a way to determine if the intervention is having an impact on the underlying process of aging. This means not just whether it has an effect on one of the body's systems, for example, affecting blood pressure or cholesterol levels, but whether it slows down the actual aging process.

Currently, the only way to test interventions that are aimed at extending life is to try them in a study and then follow the people involved until the end of their lives to see if there was any impact on extending life span. What's needed are biomarkers of the aging process that could be used to determine a person's life expectancy, making it unnecessary to wait for many years for the results of studies.

Ideally, there would be a set of these biomarkers that would identify biological age. These could be used to test whether a drug or dietary additive slowed down the aging process.

If a set of biomarkers of aging were identified, it would also have the effect of demonstrating that there actually is an underlying mechanism of aging that coordinates changes across the body's systems. It would show that there is something coordinating the changes.