Air pollution and ST-segment depression in elderly subjects.
Increased levels of daily ambient particle pollution have been associated with increased risk of cardiovascular morbidity. Black carbon (BC) is a measure of the traffic-related component of particles. We investigated associations between ambient pollution and ST-segment levels in a repeated-measures study including 269 observations on 24 active Boston residents 61-88 years of age, each observed up to 12 times from June through September 1999. The protocol involved continuous Holter electrocardiogram monitoring including 5 min of rest, 5 min of standing, 5 min of exercise outdoors, 5 min of recovery, and 20 cycles of paced breathing. Pollution-associated ST-depression was estimated for a 10th- to 90th-percentile change in BC. We calculated the average ST-segment level, referenced to the P-R isoelectric values, for each portion of the protocol. The mean BC level in the previous 12 hr, and the BC level 5 hr before testing, predicted ST-segment depression in most portions of the protocol, but the effect was strongest in the postexercise periods. During postexercise rest, an elevated BC level was associated with -0.1 mm ST-segment depression (p = 0.02 for 12-hr mean BC; p = 0.001 for 5-hr BC) in continuous models. Elevated BC also predicted increased risk of ST-segment depression > or = 0.5 mm among those with at least one episode of that level of ST-segment depression. Carbon monoxide was not a confounder of this association. ST-segment depression, possibly representing myocardial ischemia or inflammation, is associated with increased exposure to particles whose predominant source is traffic.
Gold
Diane R
DR
Channing Laboratory, Brigham and Women's Hospital, Department of Medicine, Harvard Medical School, Boston, Massachusetts 02215, USA. diane.gold@channing.harvard.edu
Litonjua
Augusto A
AA
Zanobetti
Antonella
A
Coull
Brent A
BA
Schwartz
Joel
J
MacCallum
Gail
G
Verrier
Richard L
RL
Nearing
Bruce D
BD
Canner
Marina J
MJ
Suh
Helen
H
Stone
Peter H
PH
D000368:Aged; D000369:Aged, 80 and over; D000393:Air Pollutants / Q000009:adverse effects / Q000032:analysis; D000397:Air Pollution / Q000009:adverse effects*; D002244:Carbon / Q000009:adverse effects* / Q000032:analysis; D002248:Carbon Monoxide / Q000009:adverse effects / Q000032:analysis; D004391:Dust / Q000032:analysis; D015716:Electrocardiography, Ambulatory; D004784:Environmental Monitoring; D005080:Exercise Test; D005260:Female; D006339:Heart Rate; D006801:Humans; D008297:Male; D001335:Vehicle Emissions / Q000009:adverse effects*
D000393:Air Pollutants; D004391:Dust; D001335:Vehicle Emissions; D002244:Carbon; D002248:Carbon Monoxide