Longevity and aging: beneficial effects of exposure to mild stress.

Every organism has to deal with exposure to stresses. Animals have developed various strategies to cope with stress. It appears that the developed resistance to stress is often related to longevity. Some scientists have advanced the hypothesis that the stress response may also counteract the negative effects of aging, and that exposing organisms to a mild, sublethal stress, inducing a stress response, may help them to live longer. Several mild stresses have been reported to increase longevity (irradiation, heat and cold shock, hypergravity, exercise, etc.), and one of them, hypergravity, to decrease the rate of behavioral aging. The mechanisms whereby these stresses increase longevity have not yet been elucidated. However, the studies conducted so far show that they may involve metabolic regulation and stress protein (hsps) induction.