Sitting for many hours per day is
associated with increased coronary artery calcification, a marker of
subclinical heart disease that can increase the risk of a heart attack,
according to research scheduled for presentation at the American College of
Cardiology's 64th Annual Scientific Session in San Diego. Coronary artery
disease is the most common type of heart disease and the leading cause of death
in the United States.
The study found no association
between coronary artery calcification and the amount of exercise a person gets,
suggesting that too much sitting might have a greater impact than exercise on
this particular measure of heart health. The results suggest that exercise may
not entirely counteract the negative effects of a mostly sedentary lifestyle on
coronary artery calcium.
"It's clear that exercise is
important to reduce your cardiovascular risk and improve your fitness
level," said Jacquelyn Kulinski, M.D., assistant professor of
cardiovascular medicine at the Medical College of Wisconsin and the study's
lead author. "But this study suggests that reducing how much you sit every
day may represent a more novel, companion strategy (in addition to exercise) to
help reduce your cardiovascular risk."
The research comes on the heels of
recent studies linking excess sitting with an increased risk for cardiovascular
disease, diabetes, cancer and early death. The phenomenon has been dubbed
"sitting disease," though it is a lifestyle risk factor and not a
true medical condition.
This study offers a unique
perspective on the effects of sedentary behavior because it links sitting with
an early marker for heart disease risk, laying the foundation for future
studies that could investigate whether changing your habits could potentially
reverse the damage before you develop full-blown heart disease.
Coronary artery calcification,
measured through a non-invasive CT heart scan, indicates the amount of calcium
contained in plaques within the heart's arteries. Coronary artery disease
occurs when such plaques accumulate over time, causing the arteries to narrow.
Analyzing heart scans and physical
activity records of more than 2,000 adults living in Dallas, the researchers
found each hour of sedentary time per day on average was associated with a 14
percent increase in coronary artery calcification burden. The association was
independent of exercise activity and other traditional heart disease risk
factors.
"I think the study offers a
promising message. Reducing the amount of time you sit by even an hour or two a
day could have a significant and positive impact on your future cardiovascular
health," Kulinski said.
A particular strength of the study is
that the researchers used a motion-tracking device called an accelerometer to
measure how long participants were sedentary and how much they exercised,
whereas most previous studies have relied on surveys.
"With surveys, there's more
subjectivity," Kulinski said. "With this device, we're able to log
activity levels minute-by-minute."
The results revealed participants sat
for a little more than five hours per day on average, with a range of two to 12
hours. More sedentary participants were more likely to be older, have a higher
body mass index, and have diabetes or hypertension. The analysis accounted for
these factors, as well as for income, marital status, smoking, cholesterol, and
other demographic and health-related factors. People with known cardiovascular
disease, such as a previous stroke or heart attack, were excluded from the
analysis.
"The lesson here is that it's really important to try
to move as much as possible in your daily life; for example, take a walk during
lunch, pace while talking on the phone, take the stairs instead of the elevator
and use a pedometer to track your daily steps," Kulinski said. "And
if you do have a very sedentary job, don't go home at night and sit in front of
the TV for hours on end."
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