title: Fine particulate air pollution and the progression of carotid intima-medial thickness: a prospective cohort study from the multi-ethnic study of atherosclerosis and air pollution.
abstract: BACKGROUND
  Fine particulate matter (PM2.5) has been linked to cardiovascular disease, possibly via accelerated atherosclerosis. We examined associations between the progression of the intima-medial thickness (IMT) of the common carotid artery, as an indicator of atherosclerosis, and long-term PM2.5 concentrations in participants from the Multi-Ethnic Study of Atherosclerosis (MESA).
  
  
  RESULTS
  MESA, a prospective cohort study, enrolled 6,814 participants at the baseline exam (2000-2002), with 5,660 (83%) of those participants completing two ultrasound examinations between 2000 and 2005 (mean follow-up: 2.5 years). PM2.5 was estimated over the year preceding baseline and between ultrasounds using a spatio-temporal model. Cross-sectional and longitudinal associations were examined using mixed models adjusted for confounders including age, sex, race/ethnicity, smoking, and socio-economic indicators. Among 5,362 participants (5% of participants had missing data) with a mean annual progression of 14 µm/y, 2.5 µg/m(3) higher levels of residential PM2.5 during the follow-up period were associated with 5.0 µm/y (95% CI 2.6 to 7.4 µm/y) greater IMT progressions among persons in the same metropolitan area. Although significant associations were not found with IMT progression without adjustment for metropolitan area (0.4 µm/y [95% CI -0.4 to 1.2 µm/y] per 2.5 µg/m(3)), all of the six areas showed positive associations. Greater reductions in PM2.5 over follow-up for a fixed baseline PM2.5 were also associated with slowed IMT progression (-2.8 µm/y [95% CI -1.6 to -3.9 µm/y] per 1 µg/m(3) reduction). Study limitations include the use of a surrogate measure of atherosclerosis, some loss to follow-up, and the lack of estimates for air pollution concentrations prior to 1999.
  
  
  CONCLUSIONS
  This early analysis from MESA suggests that higher long-term PM2.5 concentrations are associated with increased IMT progression and that greater reductions in PM2.5 are related to slower IMT progression. These findings, even over a relatively short follow-up period, add to the limited literature on air pollution and the progression of atherosclerotic processes in humans. If confirmed by future analyses of the full 10 years of follow-up in this cohort, these findings will help to explain associations between long-term PM2.5 concentrations and clinical cardiovascular events.
authors: Department of Epidemiology, University of Michigan, Ann Arbor, Michigan, USA. sadar@umich.edu
authors: Sara D
authors: SD
authors: Adar
authors: Lianne
authors: L
authors: Sheppard
authors: Sverre
authors: S
authors: Vedal
authors: Joseph F
authors: JF
authors: Polak
authors: Paul D
authors: PD
authors: Sampson
authors: Ana V
authors: AV
authors: Diez Roux
authors: Matthew
authors: M
authors: Budoff
authors: David R
authors: DR
authors: Jacobs
authors: R Graham
authors: RG
authors: Barr
authors: Karol
authors: K
authors: Watson
authors: Joel D
authors: JD
authors: Kaufman
mesh_terms: D000368:Aged; D000397:Air Pollution / Q000009:adverse effects* / Q000032:analysis; D050197:Atherosclerosis / Q000209:etiology / Q000473:pathology*; D059168:Carotid Intima-Media Thickness; D015331:Cohort Studies; D003430:Cross-Sectional Studies; D018450:Disease Progression; D004781:Environmental Exposure / Q000009:adverse effects* / Q000032:analysis; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D052638:Particulate Matter / Q000009:adverse effects* / Q000032:analysis; D013997:Time Factors
chemical_list: D052638:Particulate Matter
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