More evidence is showing how cumulative stress and the occurrence of disease may define age more than chronological aging.
Science Blog’s “Wear and tear of stress: the psychoneurobiology of aging” summarizes research from leading researchers in the fields of neurobiology and psychoneuroendocrinology [wiki].
“Acute stress seems to enhance immune function and improves memory but chronic stress has the opposite effect and can lead to disorders like depression, diabetes and cognitive impairment in aging.”
Cumulative stress effects are showing up in people who are under constant stress, like those in caregiver situations or those who suffer from obesity and/or diabetes. These people are more likely to have decreased telomerase activity.
Telomeres are enzymes that regulate how many times an individual cell can divide.
Telomeric sequences shorten each time the DNA replicates, which is a process that happens prior to cells dividing. When at least some of the telomeres reach a critically short length, the cell stops dividing and ages (senesces) which may cause or contribute to some age-related diseases.