Figure 2.

Underlying the ageing process is a progressive, gradual accumulation of molecular damage. Such damage is intrinsically random in nature but its rate of accumulation is regulated by genetic mechanisms for maintenance and repair. As cell defects accumulate, the effects on the body as a whole are eventually revealed as age-related frailty, disability and disease. This model accommodates the observed effects on length of life through environmental factors such as stress, nutrition, and exercise, which—in the case of adverse factors—can exacerbate the exposure to damage, and which—in the case of beneficial factors—can assist the body's maintenance and repair functions. The model therefore accommodates genetic, environmental and intrinsic chance effects on the ageing process.