[Avian2005] Psychoneurobiology of Aging

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Misty L. Trepke

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Wear and Tear of Stress: The Psychoneurobiology of Aging

American Psychological Association

 

" Age may be more related to reactions to stress and the absence of

disease rather than to a person's chronological age. "

 

Age may be more related to reactions to stress and the absence of

disease rather than to a person's chronological age, say leading

researchers in the fields of neurobiology and

psychoneuroendocrinology. And healthy aging is a good bet if stress

can be moderated along with adopting an active, healthy lifestyle.

This finding will be presented at the 114th Annual Convention of the

American Psychological Association (APA).

 

From a review of studies on how stress hormones affect the brain,

psychologist Bruce McEwen, PhD, of the Laboratory of

Neuroendocrinology at The Rockefeller University, finds more

evidence that biological and behavioral stress responses can be

adaptive in the aftermath of stress, but can also cause damage when

they are over- or under-produced and go on for a long time. " 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, " said

Dr. McEwen.

 

Cumulative stress effects, said McEwen, 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.

 

There is also more evidence that the brain is more involved in a

person's stress response than previously thought, said McEwen. The

brain interprets what is threatening, i.e., what is stressful

(whether it be public speaking or perceptions of social status) and

then regulates the behavioral and physiological responses through

the autonomic, immune and neuroendocrine systems. If the brain is

under too much stress for too long, said McEwen, " we can see

structural and functional remodeling changes that affect how it

functions. "

 

" These brain changes, which appear to be reversible, are able to

change by not only pharmaceutical agents but also by lifestyle

changes like exercise, diet and social support, " said McEwen.

 

In another review of the current literature on the interactions of

the brain, stress and the endocrine system, more evidence shows how

cumulative stress and the occurrence of disease may define age more

than chronological aging. According to the review, certain diseases

start to occur when the anabolic hormone levels start to decrease -

when the tissue builders like growth hormones, testosterone,

estrogen and thyroid functions start to drop off and when the

catabolic hormones start to increase. These hormones, the tissue

fuelers, can become too active and actually break the body down.

Cortisol - a stress hormone - can become more reactive when

responding to acute challenges as one gets older.

 

This imbalance between the anabolic and catabolic hormones is likely

to be responsible for many of the psychiatric and medical diseases

associated with aging, said researcher Elissa S. Epel, PhD, of the

University of California, San Francisco. According to a model of

neuroendocrine aging, " subtle yet chronic changes in hormonal

patterns can exert pathological effects on health over time. "

 

It is also known, said Epel, that chronically elevated cortisol

reduces lean mass, bone density and shifts fat distributions that

can precede the onset of many age-related diseases like

osteoporosis, metabolic syndrome, Alzheimer's disease and major

depression. But, she added, certain behavioral factors, like

lifestyle and exercise can modify some of these hormonal effects

that seem to accelerate aging.

 

Compared to healthy older adults under 100 years of age, healthy

centenarians, said Epel, tend to show slower insulin and glucose

rates when fasting, have higher or similar thyroid hormones and have

similar cortisol and growth hormone levels. Even though older adults

are exposed to more chronic stressors (more health problems, fewer

social connections), they do not necessarily experience greater

daily stress. The authors believe that the healthy centenarians are

using coping techniques such as finding meaning in activities and

strengthening meaningful social ties to help moderate chronic stress.

 

Centenarians also report using three coping strategies to deal with

their health problems: acceptance, not worrying and taking things

one day at a time. Those older adults who do not employ these types

of strategies, said Epel, may become more vulnerable to stress over

time.

 

Many of the neuroendocrine changes that occur with aging are not

inevitable, said Epel, and " this is demonstrated by healthy

centenarians. Certain age-related changes can be modified with

physical activity, sufficient sleep and good coping techniques. It

is when chronic stress, inactivity and added body weight take hold

that the neuroendocrine system becomes off balance. This imbalance

between the anabolic and catabolic hormones now appears to be the

most common profile of aging and may be a valuable marker for

biological aging. "