Table 1.

Demographic and health characteristics of overall study cohort and according to quartiles of annual average county PM2.5 concentrations

CharacteristicOverall CohortPM2.5 Quartile 1, 5.0–9.1 μg/m3PM2.5 Quartile 2, 9.2–11.0 μg/m3PM2.5 Quartile 3, 11.1–12.6 μg/m3PM2.5 Quartile 4, 12.7–22.1 μg/m3
No. of counties3108791 (25.45)771 (24.81)789 (25.39)757 (24.36)
No. of cohort participants 2,482,737322,251 (12.98)598,370 (24.10)621,155 (25.02)940,961 (37.90)
Median age (IQR)62.46 (54.68–71.78)64.03 (55.81–72.38)62.65 (54.89–71.64)62.42 (54.76–71.74)61.80 (54.06–71.69)
Race
 White2,036,361 (82.02)290,924 (90.28)523,520 (87.49)517,474 (83.31)704,443 (74.86)
 Black362,583 (14.60)11,755 (3.65)50,665 (8.47)90,869 (14.63)209,294 (22.24)
 Other83,793 (3.38)19,572 (6.07)24,185 (4.04)12,812 (2.06)27,224 (2.89)
Men2,363,311 (95.19)307,776 (95.51)567,783 (94.89)592,247 (95.35)895,505 (95.17)
Cancer289,110 (11.64)38,174 (11.85)67,854 (11.34)71,682 (11.54)111,400 (11.84)
Cardiovascular disease741,249 (29.86)94,163 (29.22)173,534 (29.00)189,752 (30.55)283,800 (30.16)
Chronic lung disease483,502 (19.47)65,050 (20.19)121,479 (20.30)122,786 (19.77)174,187 (18.51)
Diabetes mellitus690,144 (27.80)81,115 (25.17)161,374 (26.97)172,679 (27.80)274,976 (29.22)
Hyperlipidemia1,416,616 (57.06)185,645 (57.61)346,339 (57.88)356,589 (57.41)528,043 (56.12)
Hypertension1,669,922 (67.26)208,108 (64.58)390,968 (65.34)422,939 (68.09)647,907 (68.86)
Peripheral artery disease66,596 (2.68)8169 (2.53)16,649 (2.78)16,047 (2.58)25,731 (2.73)
Smoking status
 Current632,049 (25.46)73,416 (22.78)143,482 (23.98)161,417 (25.99)253,734 (26.97)
 Former522,016 (21.03)55,268 (17.15)120,328 (20.11)140,116 (22.56)206,304 (21.92)
 Never1,328,672 (53.52)193,567 (60.07)334,560 (55.91)319,622 (51.46)480,923 (51.11)
BMI
 Underweight25,691 (1.03)2901 (0.90)5738 (0.96)6415 (1.03)10,637 (1.13)
 Normal weight487,974 (19.65)62,600 (19.43)112,829 (18.86)120,285 (19.36)192,260 (20.43)
 Overweight977,236 (39.36)130,877 (40.61)234,486 (39.19)244,086 (39.30)367,787 (39.09)
 Obese911,836 (39.95)125,873 (39.06)245,317 (41.00)250,369 (40.31)370,277 (39.35)
ACEI/ARB use1,165,940 (46.96)146,774 (45.55)280,308 (46.85)295,063 (47.50)443,795 (47.16)
Median county particulate matter 2.5 (IQR), μg/m311.8 (10.1–13.7)8.3 (7.5–8.8)10.1 (9.8–10.6)11.8 (11.3–12.2)14.3 (13.4–15.6)
Median air sodiuma (IQR), μg/m30.05 (0.04–0.8)0.04 (0.03–0.05)0.06 (0.03–0.11)0.06 (0.04–0.11)0.05 (0.04–0.8)
Median follow-up time (IQR), yr8.52 (8.04–8.80)8.54 (8.07–8.80)8.52 (8.05–8.80)8.52 (8.04–8.80)8.52 (8.03–8.79)
Death during follow-up598,728 (24.12)75,821 (23.53)142,130 (23.75)151,109 (24.33)229,668 (24.41)
Average eGFR at T0 (SD), ml/min per 1.73 m276.26 (19.88)73.20 (18.20)76.09 (19.25)76.00 (19.80)77.60 (20.74)
Mean eGFR slope (SD), ml/min per 1.73 m2 per yr−0.79 (3.26)−0.46 (3.08)−0.72 (3.16)−0.74 (3.27)−0.97 (3.37)
eGFR slope category, ml/min per 1.73 m2 per yr
 No decline, ≥0905,033 (36.45)139,925 (43.42)223,319 (37.32)231,448 (37.26)310,341 (32.98)
 Stable decline, <0 to ≥−1632,381 (25.47)80,837 (25.09)157,018 (26.24)158,807 (25.57)235,719 (25.05)
 Moderate decline, <−1 to ≥−5757,720 (30.52)82,208 (25.51)176,639 (29.52)184,731 (29.74)314,142 (33.39)
 Rapid decline, <−5187,603 (7.56)19,281 (5.98)41,394 (6.92)46,169 (7.43)80,759 (8.58)
Median no. of outpatient eGFR measures before T0 (IQR)4 (2–8)5 (2–8)4 (2–8)4 (2–7)4 (2–7)
Median no. of outpatient eGFR measures after T0 (IQR)13 (8–20)13 (8–19)13 (8–20)13 (8–20)13 (7–20)
Median no. of hospitalizations (IQR)0 (0–0)0 (0–0)0 (0–0)0 (0–0)0 (0–0)
One or more hospitalizations411,318 (16.57)49,900 (15.48)96,800 (16.18)101,241 (16.30)163,377 (17.36)
Myocardial infarction90,019 (3.63)10,729 (3.33)20,998 (3.51)22,851 (3.68)35,411 (3.77)
Median county percent in poverty (IQR), %13.0 (10.2–15.6)12.1 (10.1–15.4)12.6 (10.5–15.2)13.1 (10.3–16.6)13.4 (10.5–15.9)
Median population density (IQR) per square mile254.9 (74.4–931.4)39.5 (15.0–224.4)166.1 (50.7–399.1)238.4 (78.0–803.0)529.7 (198.0–1801.2)
  • Data are presented as n (%) unless otherwise indicated. Covariates as measured at T0. IQR, interquartile range; ACEI, angiotensin-converting enzyme inhibitors; ARB, angiotensin receptor blockers.

  • a In a subcohort within 30 miles of an air monitoring station that measures sodium (n=1,368,122).