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Table 4 Modification of the PM10 association by city characteristics across 34 US cities

From: Particulate air pollution and survival in a COPD cohort

City   HR at the 25% Percentile HR at the 75% Percentile
Characteristics P-value for modifier 1st Quartile HR 95% CI 3rd Quartile HR 95% CI
Percent population aged 65+ in poverty status
  0.56 1.4 1.12 1.06 1.18 2.7 1.10 1.05 1.15
Annual mortality rate for emphysema in 65+
  0.19 29.5 1.09 1.04 1.14 46.9 1.12 1.07 1.17
PM 10 from traffic
  0.27 2.3 1.12 1.07 1.18 5.0 1.09 1.05 1.14
Air Conditioning
  0.77 26.0 1.11 1.06 1.17 67.0 1.10 1.04 1.16
Population density
  0.09 670.0 1.13 1.08 1.18 2344.1 1.11 1.07 1.16
Medium income
  0.26 4.3 1.13 1.07 1.18 5.6 1.10 1.05 1.14
Mean summer app temperature
  0.91 21.6 1.11 1.06 1.16 26.3 1.10 1.05 1.16
Variance of summer temperature
  0.84 11.0 1.10 1.04 1.16 21.4 1.11 1.05 1.17
  1. Results are expressed as Hazard Ratio (HR) and 95% Confidence Interval (CI) for 10 mg/m3 increase in PM10 (distributed lag) estimated at the 25th percentile and the 75th percentile of the effect modifier