The higher total daily sitting time was found to be associated with a
13% increased risk for type 2 diabetes mellitus.
When I measured how much sitting I was doing at work, and then
at home on the computer and watching television, I was absolutely
shocked! A study published in the Journal of the American Medical
Association (Pandey et al., 2016) reported that sitting 12.5 hours per
day increased risk of heart disease by 14% compared to those that
only sat for 2.5 hours per day. Now I’m no longer wondering why my
colleagues at the university have variable height desks that they can
stand or sit at.
In the late 2000’s a number of physiologists began investigations
into what was called ‘inactive physiology’ or ‘sitting physiology’ and
this began the interest in the deleterious effects of sitting on health.
Recently, Dr Bailey and his colleagues in the UK conducted a review
of the literature involving sitting and its associated development
of chronic diseases. Initially, they reported that the average adult
spends up to 60% of their waking time in sedentary behaviour, which
equated to over 8 hours per day. They conducted an electronic
search of the major databases (PubMed, Web of Science, BASE,
MEDLINE and ScienceDirect) of available research from 1989 to the
present day on studies that followed up on individuals 18 years of
age and older who were initially healthy, and their total sitting time
was measured.
Results: Initially, over 4,000 articles were identified, however only
nine with over 224,000 participants were used in this literature review.
The studies had follow-up times that ranged from 2.7 to 13 years.
The higher total daily sitting time was found to be associated with a
29% increased risk of cardiovascular disease and 13% increased risk
for type 2 diabetes mellitus. The authors explain that this increased
risk is attributed to a number of physiological mechanisms, which
result in higher levels of lipids (i.e. cholesterol), blood glucose and
insulin. They also report that prolonged sitting may result in vascular
dysfunction and hence atherosclerosis.
The thresholds for determining increased risk varied among the
studies, with some studies having the highest sitting threshold at
> 7.1 hours per day up to > 16.0 hours per day. The lowest sitting
group thresholds also varied from < 4 hours per day to < 8 hours
per day.
The authors did include information that these deleterious
effects of prolonged sitting on increased risk for cardiovascular
disease and type 2 diabetes mellitus has been shown to be reduced
in individuals who complete 60 to 75 minutes of moderate-intensity
exercise per day.
Pros: This was a good study, however additional research is
needed in sitting physiology to determine absolute thresholds for
a number of chronic diseases and what amount (and intensity) of
physical activity/exercise is needed to counteract the deleterious
effects of prolonged sitting.
Safe Work Australia recommends a number of strategies for
combatting the deleterious effects of prolonged occupational
sitting, including breaking up prolonged sitting by either standing
or walking, or a combination of standing and walking. Researchers
have recommended standing for 15 to 30 minutes per hour to attain
the health benefits. The diagram below from Safe Work Australia
(Safe Work Australia, 2019) displays examples of how the work day
can be made healthier by interspersing standing and walking in an
otherwise sedentary day.
FIGURE: Ways to reduce occupational sitting
THE QUICK READ
• The average adult spends a high proportion of their day in a
sedentary, seated position
• A comprehensive review of nine extensive studies found that
the more time people spent sitting down, the greater their risk
of heart disease and diabetes
• Exercise was found to reduce the risk of these health conditions
in people who sat for high amounts of time
• Higher blood pressure, higher elevated cholesterol levels, and
back and shoulder pain were also associated with large
amounts of sedentary time.
14 | NETWORK SPRING 2019
Image courtesy Safe Work Australia
Research by Daneshmandi et al., (2017) reported that office
workers sitting for 6.5 hours out of an 8-hour shift demonstrated
6.3% higher blood pressure and 11.2% higher elevated cholesterol,
and that over 50% had low back and shoulder problems. A study
by Suliga and colleagues (2018) reported that sitting for more than
6 hours per day resulted in an average 14% increased risk for
metabolic syndrome.
Cons: It would be beneficial for researchers to conduct a review on
available research for a number of chronic diseases and conditions
and the doses of exercise needed to offset the increased risk.