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PARTICULATE MATTER AND HEART RATE VARIABILITY AMONG ELDERLY RETIREES: THE BALTIMORE 1998 PM STUDY
Citation:
Creason, J P., L M. Neas, D B. Walsh, R Williams, L S. Sheldon, D. Liao, AND C. M. Shy. PARTICULATE MATTER AND HEART RATE VARIABILITY AMONG ELDERLY RETIREES: THE BALTIMORE 1998 PM STUDY. JOURNAL OF EXPOSURE ANALYSIS AND ENVIRONMENTAL EPIDEMIOLOGY 11:116-122, (2001).
Description:
This study investigates the reported relationship between ambient fine particle pollution and impaired cardiac autonomic control in the elderly. Heart rate variability (HRV) among 56 elderly (mean age 82) nonsmoking residents of a retirement center in Baltimore County, Maryland, was monitored for four weeks, from July 27 through August 22, 1998. The weather was seasonally mild (63 - 84 EF mean daily temperature) with low to moderate levels of fine particles (PM2.5 < 50 :g/m3). Two groups of approximately 30 subjects were examined on alternate days. A spline mixed-effects model revealed a negative relationship between outdoor 24-hour average fine particulate matter (PM2.5) and high-frequency HRV that was consistent with our earlier study for all but two days (study days four and five). The back-trajectory of the air mass on study days four and five was distinctly different from those on the other study days. Mixed-effects analysis for all 24 study days showed a small negative association of outdoor PM2.5 with high-frequency HRV (-0.03 change in log[hf HRV] for a 10 :g/m3 increment in PM2.5) after adjustment for age, sex, cardiovascular status, trend, maximum temperature, average dew point temperature, random subject intercepts, and autocorrelated residuals. After excluding study days four and five, this association was strengthened (-0.07 change in log[hf HRV] for 10 :g/m3 PM2.5, 95% CI -0.13 to -0.02) and was similar to that obtained in an earlier study (-0.12 change in log[hf HRV] for a 10 :g/m3 increment in outdoor PM2.5, 95% CI -0.24 to -0.00) (Liao et al. 1999). Acute (1 to 4 hour) previous PM2.5 exposure did not have a stronger impact than the 24-hour measure. A distributed lag model incorporating the six preceding 4-hour means also did not indicate any effect greater than that observed in the 24-hour measure. This study is supportive of other findings that exposures to PM2.5 are associated with decreased HRV in the elderly.