There are two, no three, disease or health related lifestyle
factors that I pay the most attention to when scanning research updates:
dietary intake, tobacco use and sedentary behavior. Sedentary behavior is any activity that keeps
the body relatively still, e.g., sitting
and- typing a blog post, watching TV, playing cards, reading a book,
listening to an instructor/speaker, playing video games. Past research has shown that the more a
person sits the worse it is for their health, with health defined as all-cause
mortality, chronic disease, metabolic dysfunction (high blood pressure, blood
sugar, etc.). I have already talked
about the past studies, but to review (and I don’t recall who was in the sample
studied, i.e., men, women, young, old, black, white), sitting for more than an
hour without taking a break -getting up and moving - is associated with poor
health outcomes and this is still true (with a weaker effect) if the person
doing the uninterrupted sitting also exercises for an hour or so a day. So physical activity is good, sedentary behavior
is bad, and sedentary behavior is bad (deleterious) for inactive AND active
people.
So that was old news.
This week I read another study about the benefits of breaking up
sedentary time. The study by Sardinha, Santos, Silva, Baptista, & Owen (2014)
specifically focused on Portuguese adults between the ages of 65 and 94, but it
is likely that the same metabolic processes happen in older adults of other
races/nationalities though the effect may be higher or lower. An example; if sedentary behavior increased
the risk of all-cause mortality by 2% in one group, it would probably increase
the risk in a similar group, but the increase (effect) might be 1% or 5%
instead. Sedentary behavior is still
bad, just more or less so.
The current study was a little different from those that
came before, and that is a good thing, because it makes the evidence stronger. Here the researchers included measures
specific to an older person’s physical activity
level, physical functioning and physical independence. The participants wore accelerometers on their
hips during the day for four days. The
accelerators recorded information on movement that the researchers could turn
into activity levels. The researchers
took several measures of physical functioning,
including, how many times a person could sit and stand from a chair in 30sec,
how many dumbbell curls they could do in 30sec, and how far they could walk in
6 minutes. The researchers measured
physical independence with a 12 item
scale with a total of 0 to 24 points. Items
include questions about one’s ability to do an activity with or without
assistance, e.g., bathe, do laundry, walk, etc.
I found an example of both tests, if you’d like to see them click here
for the physical function test and here
for independence test.
For the outcome of interest, Sardinha et al focused on differences
in persons’ physical functioning abilities (e.g., the dumbbell activity) and a
score that totaled all those physical function abilities. These measures matter
because they are important indicators of successful vs usual aging. Sardinha et al compared the functional
measures, while controlling for persons’ physical activity levels (do they get
the recommend 30 minutes a day of moderate to vigorous physical activity/ yes
or no; based on the accelerometer data), independence test scores (described in
the above paragraph), BMI, sex and some other things. They wanted to see if peoples’ scores were
different based on the amount of time they spent in sedentary behavior (sb) and
whether or not that time is broken up; breaks in sedentary behavior (BST).
And of course, the scores were different. In the analysis of the physical function
components and the overall score, there were higher scores in the dumbbell curl,
the chair test and the overall score, when people took breaks in their
sedentary time. The researchers also looked at the direct and independent
effect of moderate-vigorous physical activity (cycling, aerobics, running),
sedentary time and breaks in sedentary time on the total physical function
score and found that people who engage in at least 30 min of moderate to
vigorous physical activity a day have higher scores, people who spend the most
time in sedentary behavior have the lowest scores and those who take breaks
have higher scores than those who do not.
I leave you with a quote from the authors’ conclusion
section:
Therefore, PA [physical activity]
guidelines for older adults might emphasize more strongly these two distinct
behaviors to be considered together, such that even if a person were to comply
with 30 min/d of MVPA, they should avoid too much sitting for the rest of the
day. Periodic and small interruptions to SB [sedentary behavior] are likely to
be of importance in preventing a decline in physical function.
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