As anyone that has read my blogs knows, I’m very interested
in exercise and training, with a particular interest in geriatrics—I guess
that’s because I am one!
I’ve written before that the amount of literature reporting
on exercise and old folks is dwarfed by that reported on in the young; however,
there have been several very interesting, recent reports regarding older adults.
The need for studies on the effect of exercise on older
adults is urgent. 34% of US adults over
the age of 70 have walking limitations; those reporting such limitations have a
four times higher risk of needing nursing
home placement and are three times more likely to die than those with no
walking difficulty.
That exercise lowers medical costs has been shown. Studies have demonstrated that ON AVERAGE
exercise improves physical function.
However, there are some niggling little facts associated with studies on
older adults that are not generally known: not
all participants in studies show improvement from exercise. What??
For example, in a small 2005 study of adults over the age of
60 who were overweight had knee osteoarthritis, and who participated in
exercise training for 6 months (aerobic and resistance exercise), 7.5% showed
no increase in walking distance and 58% showed no increase in muscle
strength. Ouch.
What’s going on here? Exercise is hard enough,
let alone if you get no benefit out of it.
A study published in 2012 came up with related similar results
looking at changes in insulin as well as high density cholesterol: an analysis
of 1,687 adults over six studies concluded that 8.3% of participants had worse
insulin numbers, and 13.3% had worse cholesterol results.
The point being that a portion of the population does not
respond to exercise. Or they may even get
worse.
So, what accounts for this variation from individual to
individual? Well, there are of course environmental reasons—but there are
potentially genetic reasons, too.
The exercise literature has been examining one particular
gene for more than a decade—the ACE gene (“angiotensin-converting
enzyme”). Everyone has an ACE gene, and
there are two different types (alleles), called the “I” gene and the “D”
gene.
Therefore, people can be either II, ID, or DD for the ACE
gene.
There have been many many studies on the ACE gene and
athletic performance in young athletes.
IN GENERAL the I gene is found in elite endurance athletes—long distance
runners, cyclists, rowers, and mountaineers.
The D gene is associated with “power” athletes such as sprinters or those
that excel in strength related events. I
should add that there are studies that show the opposite results—however, the preponderance
of the evidence is as I state above.
This seems to be an emerging pattern with respect to the genetics of
athletic ability.
It may not be surprising, therefore, that ACE genotypes have
been looked at with respect to how old folks respond to exercise—the question
being, “is some of the variability in older adults responses
to exercise dependent on their ACE genes?”
There are at least two long-term studies involving oldsters
and exercise. One is the Health ABC
study and the other is the Lifestyle Intervention and Independence for
Elders Pilot (LIFE-P).
The Health ABC study started in 1997 and 1998. It enrolled about 3,000 people, males and
females, whites and blacks, ages 70-79.
They had to be “normal,” with no limitation in their ability to walk a
quarter mile or go up 10 steps without resting.
In 2005 a study analyzed these folks. They found that at the initial start of the
study there was NO difference between II, ID, and DD genotypes for a wide
variety of characteristics such as weight, diabetes, hypertension, physical activity,
etc. (Further, as points of reference, the frequency of the II type was 19.2%,
33.6% were DD, and 47.2% were ID).
However, after 4 years they classified the people according
to their level of physical activity, genotype, AND degree of “mobility limitation”
(difficulty in walking a quarter mile or going up 10 steps without resting). What they found was 1) the group that was
most active had 18% less mobility limitation than the inactive group (providing
more evidence that activity is good); 2)
that within the group that had very
low physical activity over the 4 years there was no difference between the
genotypes; and 3) in the most active group the II, ID, and DD genotypes
differed.
So, of interest here is point 3 above: in the most active
group the II, ID, and DD genotypes differed in their response to exercise. The II having the most mobility limitation
and the ID and DD having the least; the difference between the II and ID OR DD
being 45%.
Wow. A 45% difference
in mobility limitation. The II genotype
had HALF of the benefit of exercise compared with either ID or DD genotypes,
and those that did weight lifting the greatest benefit. Also, the II genotype had a higher percentage
of body fat.
So, although exercise reduced mobility limitation, the II
genotype had the poorest response. And remember they represent 19% of the
population.
The LIFE-P study is smaller than the Health ABC study, and started
in in 2004. It enrolled around 400 men
and women who were 70-85 years old, who were able to walk 400 meters within 15
minutes, had a sedentary life style (spent less than 20 minutes per week on
regular physical activity), and scored less than 10 on the SPPB test
(discussed below). Persons with physical infirmaries, cardiac
issues, and diseases of various types were excluded.
The SPPB test (Short Physical Performance Battery) has
become a kind of gold standard for quickly assessing physical capability for
old folks. The test includes determining
how long it takes to get up and down out of a chair 5 times, how long one
balances one’s self with the feet side by side or positioned heel to toe, and
how long it takes to walk EIGHT (8) FEET, with a maximum score being less than 3.1 seconds. (Just reading these requirements almost makes
me cry!).
An SPPB score of 10 or less (maximum of 12), means that
there were “some” strength and balance issues
So in other words, these are older people who were pretty
“normal” without major health issues.
There are around 400 people enrolled in the LIFE-P
study. Since 2006 there have been
several studies published on this group of people. A very early study, conducted after the
program had been started for a little more than a year, showed that indeed, and
unsurprisingly, individuals subjected to a combination of strength, aerobic,
balance, and flexibility exercises performed better on SPPB test one year later
than another group that only received exercise instruction.
A study published in 2014 on 283 individuals enrolled in the
LIFE-P study looked at those that were subjected to exercise vs. no exercise,
and who were further classified into II, ID, and DD genotypes. Exercise consisted of walking, strength,
flexibility, and balance training. The strength exercises consisted of standing
chair squats, toe stands, leg curls, knee extensions, and side hip rises with
ankle weights.
So, first they found that those enrolled in the exercise
group (E), maintained their SPPB score, while those that did not exercise (NE)
significantly declined in their score.
Once again showing that exercise maintains performance. But, of importance to this blog, in the E
group there was a wide variation in SPPB score, with 33% experiencing a DECLINE
in performance compared to 37% who showed a 2-point improvement in their
score.
So, with exercise, as with the Health ABC, a significant
percentage of those had NO BENEFIT. I suppose
you can guess what comes next: they also looked at II, ID, and DD genotypes.
And what they found was, you guessed it (!), the II genotype
had no or decreased performance—again like the Health ABC study.
If this is borne out by future studies, then this
is huge, in my opinion. It may totally
change how older adults are counseled with respect to exercise. It is possible that some genotypes benefit
most by, for example, walking, while others benefit most by doing strength
exercises.
Helpful Resources:
http://jama.jamanetwork.com/article.aspx?articleid=201372
http://link.springer.com/article/10.2165/00007256-200838120-00008/fulltext.html
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2657174/
https://www.google.com/webhp?sourceid=chrome-instant&ion=1&espv=2&ie=UTF-8#q=effects%20of%20a%20physical%20activity%20intervention%20on%20measures%20of%20physical%20performance
