214
U N I T 2
Integrative Body Functions
reported decline in ANS and cardiovascular responsive-
ness to stress associated with advancing age.
39
Aging is
also associated with impaired activation and proliferation
of T and B lymphocytes, as well as poorer natural killer
cell response to stimulatory cytokines.
40
Gender.
Within the last decade, primarily because females
have been included in basic science and clinical investi-
gations, differences between the sexes in cardiovascular,
respiratory, endocrine, renal, and neurophysiologic func-
tion have been found, and it has been hypothesized that
sex hormones are the basis of these biologic differences.
Technological advances in cellular and molecular biology
have made it clear, however, that there are fundamental
differences in the locale and regulation of individual genes
in the male and female genome that can account at a very
basic level for differences in physiologic function and
disease manifestation.
41
These differences have general
implications for the prevention, diagnosis, and treatment
of disease and specific implications for our understanding
of the sex-based differences in response to life’s stressors.
Given the nature of sex-based differences, it is not sur-
prising that there are differences in the physiologic stress
response in both the HPA axis and the ANS. For example,
the male hypothalamus produces more CRF and more
ACTH than the premenopausal female hypothalamus,
in response to psychological stressors (e.g., public speak-
ing).
42
However, secretion of arginine vasopressin (AVP),
a hormone that has cardiovascular and renal effects and
potentiates the release of ACTH, is greater in the female.
Premenopausal women also tend to have a lower activa-
tion of the SNS than men in response to stressors. The
phase of menstruation (luteal vs. follicular), as well as
menopausal status, can alter these responses and need to
be considered when studying these responses.
42
These sex-
based differences in activation of the stress response may
partially explain differences in susceptibility to diseases
in which the stress response may play a causal role. These
research results are not definitive, but they are intriguing
and may serve as a foundation for further research.
Health Status.
Physical and mental health status deter-
mine physiologic and psychological reserves, and they
are strong determinants of one’s ability to adapt. For
example, persons with heart disease are less able to adjust
to stressors that require recruitment of cardiovascular
responses. Severe emotional stress often produces disrup-
tion of physiologic function and limits the ability to make
appropriate choices related to long-term adaptive needs.
Professionals who have worked with acutely ill persons
have witnessed that the will to live often has a profound
influence on survival during life-threatening illnesses.
Nutrition.
There are 50 to 60 essential nutrients, includ-
ing minerals, lipids, certain fatty acids, vitamins, and spe-
cific amino acids. Deficiencies or excesses of any of these
nutrients can alter a person’s health status and impair
the ability to adapt. The importance of nutrition to
enzyme function, immune response, and wound healing
is well known. On a worldwide basis, malnutrition may
be one of the most common causes of immunodeficiency.
Among problems associated with dietary excess are
obesity and alcohol abuse. Obesity is a common problem.
It predisposes an individual to a number of health prob-
lems, including atherosclerosis and hypertension. Alcohol
is commonly used in excess. It acutely affects brain func-
tion, and with long-term use, can seriously impair func-
tion of the liver, brain, and other vital structures.
Sleep–Wake Cycles.
Sleep is considered to be a restor-
ative function, in which energy is restored and tissues
are regenerated.
43
Sleep occurs in a cyclical manner,
alternating with periods of wakefulness and increased
energy use. Biologic rhythms play an important role
in adaptation to stress, development of illness, and
response to medical treatment. Many rhythms such
as rest and activity, work and leisure, and eating and
drinking oscillate with a frequency similar to that of the
24-hour light–dark solar day. The term
circadian,
from
the Latin
circa
(“about”) and
dies
(“day”), is used to
describe these 24-hour diurnal rhythms.
Sleep disorders and alterations in the sleep–wake cycle
have been shown to alter immune function, the normal
circadian pattern of hormone secretion, and physical
and psychological functioning.
44
The two most com-
mon manifestations of an alteration in the sleep–wake
cycle are insomnia and sleep deprivation or increased
somnolence. In some persons, stress may produce sleep
disorders; in others, sleep disorders may lead to stress.
Acute stress and environmental disturbances, loss of a
loved one, recovery from surgery, and pain are common
causes of transient and short-term insomnia. Air travel
and jet lag constitute additional causes of altered sleep–
wake cycles, as does shift work.
Hardiness.
Studies by social psychologists have focused
on individuals’ emotional reactions to stressful situations
and use of coping mechanisms in order to determine
characteristics that help some people remain healthy
despite being challenged by high levels of stressors. For
example, the concept of
hardiness
describes a personality
characteristic that includes a sense of having control over
the environment, a sense of having a purpose in life, and
an ability to conceptualize stressors as a challenge rather
than a threat.
45
Lower levels of hardiness have been linked
with greater reaction to stress, including suppressed pro-
inflammatory cytokines (IL-12), increased anti-inflamma-
tory cytokines (IL-4, IL-10), and lower neuropeptide-Y
levels. Individuals with higher levels of psychological har-
diness demonstrated more moderate and healthy immune
and neuroendocrine responses to stress.
46
Psychosocial Factors.
Several studies have related
social factors and life events to illness. Scientific inter-
est in the social environment as a cause of stress has
gradually broadened to include the social environment
as a resource that modulates the relationship between
stress and health. Presumably, persons who can mobi-
lize strong supportive resources from within their social
relationships are better able to withstand the negative
effects of stress on their health. Studies suggest that
social support has direct and indirect positive effects on
