C. Arden Pope III, PhD,
Richard L. Verrier, PhD, Eric G. Lovett, PhD, Andrew C. Larson, BS, Mark
E. Raizenne, BA, BSc, Richard E. Kanner, MD, Joel Schwartz, PhD, G. Martin
Villegas, BS, Diane R. Gold, MD, Douglas W. Dockery, ScD
Brigham Young University,
Provo, Utah; Institute for Prevention of Cardiovascular Disease, Beth
Israel Deaconess Medical Center, Harvard Medical School, Boston, Mass;
Marquette Medical Systems, Milwaukee, Wis; Health Canada, Ottawa, Ontario,
Canada; University of Utah School of Medicine, Salt Lake City, Utah; Channing
Laboratory, Brigham and Women's Hospital, Harvard Medical School, and
Harvard School of Public Health, Boston, Mass.
Am Heart J 138(5):890-899,
1999
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Background:
Epidemiologic studies have linked fine particulate air pollution with
cardiopulmonary mortality, yet underlying biologic mechanisms remain unknown.
Changes in heart rate variability (HRV) may reflect changes in cardiac
autonomic function and risk of sudden cardiac death. This study evaluated
changes in mean heart rate and HRV in human beings associated with changes
in exposure to particulate air pollution.
Methods:
Repeated ambulatory electrocardiographic monitoring was conducted on 7
subjects for a total of 29 person-days before, during, and after episodes
of elevated pollution. Mean HR, the standard deviation of normal-to-normal
(NN) intervals (SDNN), the standard deviation of the averages of NN intervals
in all 5-minute segments of the recording (SDANN), and the square root
of the mean of squared differences between adjacent NN intervals (r-MSSD)
were calculated for 24-hour and 6-hour time segments. Associations of
HRV with particulate pollution levels were evaluated with fixed-effects
regression models.
Results:
After controlling for differences across patients, elevated particulate
levels were associated with (1) increased mean HR, (2) decreased SDNN,
a measure of overall HRV, (3) decreased SDANN, a measure that corresponds
to ultralow frequency variability, and (4) increased r-MSSD, a measure
that corresponds to high-frequency variability. The associations between
HRV and particulates were small but persisted even after controlling for
mean HR.
Conclusions:
This study suggests that changes in cardiac autonomic function reflected
by changes in mean HR and HRV may be part of the pathophysiologic mechanisms
or pathways linking cardiovascular mortality and particulate air pollution.
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