We
all understand that acute, brief increases in stress levels will
manifest themselves physiologically in elevated heart rate, breathing
and blood pressure as well as increased production of cortisol.
Short-term, the body can deal with these momentary surges. On the other
hand, long-term, chronic stress can lead directly to disease states and
increased mortality. While most people are resilient and can deal with a
major stress event or two each year, long-term, even moderate stress
over time can have devastating effects, many of which affect unseen or
hidden aspects of our physiology.
A new study concludes, for example, that men who experience
persistently moderate to high levels of stressful life events over a
number of years have a 50 percent higher mortality rate.
In this study, those in the low stress group experienced an average of
two or fewer major life events in a year, compared with an average of 3
for the moderate group and up to 6 for the high stress group. One of the
study's most surprising findings was that the mortality risk was
similar for the moderate versus high stress group. Life-affecting events
include divorce, death and major illness for instance.
Stress and epigenetics
While the above may not seem earth-shattering, perhaps the prospect
of the stress you experience possibly affecting future generations may.
While I have blogged about epigenetics in the past, stress can now be
considered as an epigenetic factor. To redefine, epigenetics mean
changes in genetic expression that are not caused by actual changes in
DNA sequencing. In other words, genes are very active and respond to
many environmental factors including toxins, stress and diet for
example. These environmental forces can cause genes to “switch on and
off,” regulating gene expression and consequently having phenotypic
effects.
In a fascinating new study, researchers found that the progeny of
mice, primarily the males, exposed to chronic stress were astoundingly
affected phenotypically and hormonally with dysmasculinization characteristics very apparent.
The results suggest exposure to stress during early pregnancy can lead
to long-term changes in offspring that can be passed across generations.
In a similar study, researchers investigated paternal effects and found that male mice exposed to chronic stress pass those stress behaviors along to their offspring.
Both their male and female progeny showed increased depression and
anxiety-like behaviors, although the effects were again stronger in
males.
The link to hypertension
While this result is alarming enough, stress manifests itself
physiologically in a number of ways. For example, a recent study
elaborated on possible mechanisms that contribute to progression of
hypertension. The study detailed how stress-induced T-cell activation increased hypertension, suggesting a relation between a stress-induced inflammatory response and the immune system.
Stress and the brain
Additionally, another study has shown that repeated stress triggers the production and accumulation of insoluble tau protein aggregates
inside the brain cells of mice. These aggregates are similar to
neurofibrillary tangles, the modified protein structures that are one of
the physiological hallmarks of Alzheimer's disease. Additionally, the
chronic production of cortisol will also impact those with a genetic predisposition to Alzheimer’s to a greater degree than those genetically predisposed who experience low levels of stress.
Another
unseen effect of stress is shortening of telomeres. Telomeres are
protective caps on the ends of chromosomes and are now considered
indicators of aging, as they naturally shorten over time. Both stress
and depression have repeatedly been linked with premature telomere shortening and consequently premature aging.
Finally, breast tumor aggressiveness has also been associated with high levels of stress,
although there is a racial bias with black and Hispanics demonstrating
higher levels of stress and more aggressive breast tumors.
While it’s well known how impactful chronic stress can be on human
physiology, the levels to which it can negatively alter so many aspects
of our biochemistry, morphology and cellular physiology are truly
astounding and insightful.
by Michael Fuhrman D.C.
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