Table 1.

Baseline characteristics of 282,925 individuals in the primary cohorta

CharacteristiceGFR ml/min per 1.73 m2
≥90 (n=36,816)60–89 (n=168,115)45–59 (n=48,024)30–44 (n=20,240)15–29 (n=5202)Dialysis (n=4528)
Age, yr68.8±3.574.2±6.5b77.5±7.2b79.8±7.5b80.5±7.9b75.7±6.4b
Women, n (%)21,498 (58.4)93,576 (55.7)29,780 (62.0)13,424 (66.3)b3378 (64.9)b2104 (46.5)b
Income, lowest quintile, n (%)6894 (18.7)31,460 (18.7)9662 (20.1)4497 (22.2)1222 (23.5)b1095 (24.2)b
Rural residence,c n (%)3163 (8.6)16,729 (10.0)5499 (11.5)2529 (12.5)b758 (14.6)b593 (13.1)b
eGFR, ml/min per 1.73 m293.6±3.476.3±8.8b53.4±4.2b38.9±4.2b24.7±3.9b
Comorbidities
 Charlson comorbidity indexd0 (0–0)0 (0–0)2 (2–2)b2 (2–2)b2 (2–3)b3 (2–5)b
 Coronary artery disease, n (%)10,296 (28.0)58,468 (34.8)b20,544 (42.8)b10,089 (49.8)b2856 (54.9)b2641 (58.3)b
 Diabetes mellitus, n (%)13,938 (37.9)53,460 (31.8)b15,893 (33.1)7604 (37.6)2272 (43.7)b2474 (54.6)b
 Heart failure, n (%)2060 (5.6)14,513 (8.6)b7524 (15.7)b4987 (24.6)b1810 (34.8)b2128 (47.0)b
 Hypertension, n (%)21,638 (58.8)107,756 (64.1)b35,789 (74.5)b16,400 (81.0)b4342 (83.5)b3768 (83.2)b
 Peripheral vascular disease, n (%)336 (0.9)1933 (1.1)1011 (2.1)672 (3.3)b274 (5.3)b484 (10.7)b
Medications
 Loop diuretics, n (%)1442 (3.9)10,158 (6.0)6038 (12.6)b4645 (22.9)b2045 (39.3)b2526 (55.8)b
 Potassium-sparing diuretics, n (%)979 (2.7)6006 (3.6)3546 (7.4)b2305 (11.4)b610 (11.7)b257 (5.7)b
 Thiazide diuretics, n (%)5703 (15.5)30,034 (17.9)11,043 (23.0)b5262 (26.0)b1257 (24.2)b960 (21.2)b
  • Data are presented as number (%) except for age and eGFR which are presented as mean±SD. The Charlson comorbidity index is presented as a median (interquartile range).

  • a Standardized differences were used to compare baseline characteristics between the referent group (eGFR≥90 ml/min per 1.73 m2) and the other five groups (eGFR 60–89 ml/min per 1.73 m2, 45–59, 30–44, 15–29, and chronic dialysis). Standardized differences are less sensitive to sample size than traditional hypothesis tests. They provide a measure of the difference between groups divided by the pooled SD; a value >10% is interpreted as a meaningful difference between groups.

  • b Denotes a meaningful difference (>10%).

  • c Refers to location of residence with a population size <10,000 persons.

  • d All individuals with an eGFR<60 ml/min per 1.73 m2 with a Charlson comorbidity index of 0 were given a score of 2 and those with a score of 1 were given a score of 3; one of the variables in the Charlson comorbidity index is presence of kidney disease which automatically results in these individuals receiving a score of 2.