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Longer
sleep linked with lower incidence of
Calcification in Coronary Arteries
Newswise — Participants in a study who slept
on average an hour longer per night than
other participants had an associated lower
incidence of coronary artery calcification,
which is thought to be a predictor of future
heart disease, according to a study in the
December 24/31 issue of JAMA.
Risk factors for coronary artery
calcification (the accumulation of calcified
plaques visible by computed tomography [a
method of imaging body organs]) include
established heart disease risk factors such
as male sex, older age, glucose intolerance,
tobacco use, dyslipidemia (disorders of
lipoprotein metabolism, which includes high
cholesterol levels), high blood pressure,
obesity, raised inflammatory markers and
attaining a low educational level.
Recent data suggest that sleep quantity and
quality are connected to several of these
risk factors.
“However, some of these correlations have
only been documented in studies in which
sleep is measured by self-report, which may
be biased or insufficiently accurate,” the
authors write.
Christopher Ryan King, B.S., of the
University of Chicago, and colleagues tested
whether objectively measured sleep duration
predicted the development of calcification
over 5 years of follow-up.
The study included 495 participants from the
Coronary Artery Risk Development in Young
Adults [CARDIA] study, who were black and
white men and women age 35-47 years.
At the start of the study in 2000-2001, the
participants had no evidence of detectable
coronary calcification on computed
tomography scans.
Potential confounders (factors that can
possibly influence the results; age, sex,
race, education, apnea risk, smoking status)
and mediators (lipids, blood pressure, body
mass index, diabetes, inflammatory markers,
alcohol consumption, depression, hostility,
self-reported medical conditions) were
measured at both the start of the study and
at 5-year follow-up.
Sleep metrics (wrist actigraphy [monitors
rest and activity] measured sleep duration
and sleep fragmentation, daytime sleepiness,
overall sleep quality, self-reported sleep
duration) were examined for association with
new calcification, based on computed
tomography performed in 2005-2006.
The incidence of calcification at 5 years
was 12.3 percent (n = 61 participants).
After adjusting for age, sex, race,
education, smoking and apnea risk, the
researchers found that one hour more of
sleep per night decreased the estimated odds
of calcification by 33 percent.
The magnitude of the observed association
was similar to sizable differences in
established coronary risk factors (e.g., 1
additional hour of sleep reduced risk
similarly to a reduction of 16.5 mm Hg in
systolic blood pressure).
No potential mediators appreciably altered
the magnitude or significance of sleep.
Alternative sleep metrics were not
significantly associated with calcification.
“We have found a robust and novel
association between objectively measured
sleep duration and 5-year incidence of
coronary artery calcification,” the authors
write.
“This study further demonstrates the utility
of a simple objective measure of sleep that
can be used at home. Future studies will be
needed for crucial extensions to these
results.
"First,
these results need confirmation in other
cohorts.
"Second,
does sleep moderate the rate at which
calcification accumulates?
"Third,
will objective sleep tie to coronary disease
event outcomes over the long term?
"While calcification predicts such outcomes,
it is difficult to know how and if the
predictors of calcification themselves will
determine outcomes, or if their impact will
be purely mediated by their effect on
calcification.
"Finally, if this association is born out,
interventional studies will be needed to
guide clinical advice.”
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