The hippocampus is one of the
most important components of the human brain. Part of the limbic system, it
plays a major role in consolidating the short and long term memory related
information, as well as in space orientation. The two hippocampi of the humans
are located underneath the cerebral cortex, each in its brain hemisphere.
Damages to it bring
about memory losses and disorientation, the main causes of damage being chronic
stress, age, affections like Alzheimer, but also oxygen deprivation, medial
temporal lobe epilepsy or encephalitis.
While research shows
that the effects of chronic stress on the hippocampus’ structure and
functioning are quite similar to age related decline, physical exercise has
been proven to be beneficial for older adults.
The purpose of the
investigation under discussion is to examine the effects of everyday stress on
the volume of the hippocampus and on the human memory, the role played by
stress in age effects and the way exercising influences these effects.
If the hypothesis
that physical exercise is beneficial in lowering the effects of lifetime stress
on the hippocampus, and, implicitly, on the cognitive functions proves true,
based on further studies and assessments, exercise routines meant to fight
stress effects and help old adults prevent memory decline could be developed.
Methods
The study was
performed on 91 adults, 51 recruited as a result of advertising in the St.Louis
media and 40 recruited from the Alzheimer’s Disease Research Center within Washington
University.
The MRI scans of the
91 participants were combined and analyzed. Also, all of them were screened for
conditions that could affect their cognitive functions and ability to perform
physical exercises, like dementia, Parkinson’s, severe head injuries, diabetes,
etc.
Lifetime stress, exercise
engagement, hippocampal volumes (through MRI) and cognitive performances
(memory, vocabulary) were accurately measured for all the participants using
proven and acknowledged methods. Also, all participants were evaluated in order
to determine possible depression signs.
There were, however,
certain limitations that could raise doubts on the relevancy of the research
under discussion, such as:
- The investigation relies on the reports of the participants regarding lifetime stress and physical exercise measurements, and, especially since the participants are older adults, they may not recall everything accurately;
- The preliminary tests were administered by phone, without the opportunity to assess or control the circumstances that an in-person administration could have offered;
- The cognitive status assessment for the Community samples did not cover all time points, so some of the participants could have experienced a decline in the cognitive functions in the time period between the measurements;
- The exercise engagement measurements referred mostly to cardiorespiratory fitness;
- There were some timing differences between the several assessments. The measurements of lifetime stress and exercise engagement focused on experiences and behaviors during the cognitive assessment or MRI scan. For most participants, the exercise engagement measurements focused on the period when the stressful experiences were reported. There is, however, a period of approximately six months in which exercise engagement could have been subsequent to stressful experiences.
Results
The study showed the
following:
- Lifetime stress, as reported by participants, had an obvious and considerable negative influence on the hippocampal volume, without influencing the volume of the primary visual cortex.
- The negative effects of lifetime stress at the level of the hippocampus were moderated by the participants’ exercise engagement, meaning that the decline in hippocampal volume caused by stress was lower for the group with a more consistent exercise routine.
- Lifetime stress had no impact on the vocabulary of the participants, and, although it had a negative effect on their memory performance, the changes were not significant. Memory decline as a result of lifetime stress was only observed in the low exercise group members.
- Although this was not the focus of the study, the observations and measurements confirmed several positive effects of exercise, like improved angiogenesis and neurogenesis, lower stress hormones levels, reversal of the HPA dysregulation induced by corticosterone and lower response in the HPA axis to mild psychological stress factors, which supports the use of exercise as means to prevent the potentially negative effects of stress on the structure of the hippocampus and on the memory functioning.
- No major stress-age interactions were noticed as far as the volume of the hippocampus and the memory performance were concerned. Thus, nothing supports the hypothesis according to which the people experiencing greater stress also experience greater decline with age.
To sum up, the
results of the study clearly show that, while stress has significant negative
effects on the volume of the hippocampus, exercise engagement can decrease or
even completely eliminate such effects.
Otherwise put,
exercise engagement can be a solution to delay the effects of stress and aging
on the cognitive functions of late adults, and even help sufferers of Alzheimer
(considering that Alzheimer was proven to be favored by stress) and other
diseases that involve memory decline and atrophy of the hippocampus.
Discussion
Although the hypothesis
the investigation begins from is sustained by previous studies and would be a
great starting point in preventing cognitive functioning decline in late
adulthood, the actual research seems to have a few weaknesses, admitted by
those who conducted it in the first place.
The choice of the
participants, the way the screening and testing were performed, the timing,
they could have all reached higher standards. However, the tests and
measurements were based on accepted and acknowledged methods and the results
were interpreted taking the potential variables into account, so the
conclusions of the research are unquestionable.
As far as lifespan
development is concerned, the investigation under discussion is just a small
step in proving the beneficial effects of exercising. It takes into account
aspects like the general state of health of the participants, their state of
mind, their ability to interact with the other participants, their ability to
focus on certain activities and to cope with more challenging daily routines
remaining to be investigated.
Conclusions
While stress was
proven to have negative effects on the hippocampus and, implicitly, on the
cognitive functions of old adults, exercise engagement was shown to diminish
these effects. On a larger scale, this means that exercise engagement has
significant positive effects on the cognitive functions in late adulthood and
favors lifespan development.
There was definitely
room for improvement in the way the research was conducted, as the participants
could have been chosen based on better established criteria, tested and
screened in person, at the same time intervals and using the same methods and
equipment, with lifetime stress and exercise engagement measured directly, and
not based on their memories.
The research paper,
on the other hand, is very accurate and well structured, explaining every step
of the procedure, acknowledging all the above mentioned limitations and even
taking them into account as variables when interpreting the results.
Its authors
recommend that further investigations be made regarding:
- The effects of stress and exercise engagement on various regions of the brain at various ages, from childhood to adolescence, adulthood and old age.
- Individual changes in the structure and functioning of the brain according to various stressful experiences and stress – exercise interactions.
In my opinion, the
effects of stress and especially of exercise engagement on the cognitive
functioning in late adulthood could be a lot easier evaluated in nursing
facilities, where the various factors that could affect the response of the
participants could be easily identified and controlled, and the efficiency of
various exercise routines could be tested.
Considering that
exercise was already proven to have beneficial effects on health and cognitive
functions, the residents of the nursing facilities could be easily convinced to
participate in such investigations and bring their contribution to the lifespan
development of the generations following theirs.
All in all, the
current research brings about valuable information and confirmations,
representing a thorough foundation for similar future investigations.
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