ENVIRONMENTAL EXPOSURE

Association between short term exposure to fine particulate matter and heart rate variability in older subjects with and without heart disease

J H Sullivan, A B Schreuder, C A Trenga, S L-J Liu, T V Larson, J Q Koenig, J D Kaufman

Departments of Environmental and Occupational Health Sciences, Civil and Environmental Engineering, Biostatistics, and Medicine, University of Washington, Seattle, USA

Correspondence to:
Correspondence to:
Dr J H Sullivan
Northwest Particulate Matter Center, Suite 355, 1107 NE 45th Street, Seattle 98105, USA; sulljh{at}u.washington.edu

Background: Short term increases in exposure to particulate matter (PM) air pollution are associated with increased cardiovascular morbidity and mortality. The mechanism behind this effect is unclear, although changes in autonomic control have been observed. It was hypothesised that increases in fine PM measured at the subjects’ home in the preceding hour would be associated with decreased high frequency heart rate variability (HF-HRV) in individuals with pre-existing cardiac disease.

Methods: Two hundred and eighty five daily 20 minute measures of HRV (including a paced breathing protocol) were made in the homes of 34 elderly individuals with (n = 21) and without (n = 13) cardiovascular disease (CVD) over a 10 day period in Seattle between February 2000 and March 2002. Fine PM was continuously measured by nephelometry at the individuals’ homes.

Results: The median age of the study population was 77 years (range 57–87) and 44% were male. Models that adjusted for health status, relative humidity, temperature, mean heart rate, and medication use did not find a significant association between a 10 µg/m³ increase in 1 hour mean outdoor PM_2.5 before the HRV measurement and a change in HF-HRV power in individuals with CVD (3% increase in median HF-HRV (95% CI –19 to 32)) or without CVD (5% decrease in median HF-HRV (95% CI –34 to 36)). Similarly, no association was evident using 4 hour and 24 hour mean outdoor PM_2.5 exposures before the HRV measurement.

Conclusion: No association was found between increased residence levels of fine PM and frequency domain measures of HRV in elderly individuals.

Abbreviations: AICD, automatic implantable cardioverter defribillator; CVD, cardiovascular disease; HRV, heart rate variability; MI, myocardial infarction; PM, particulate matter

Keywords: air pollution; heart rate variability; cardiovascular disease; elderly

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