Table 1.

Baseline characteristics

CharacteristicUrban (n=163,592)Micropolitan (n=20,811)Rural (n=20,060)P Value
Demographic
 age (yr)63.0±15.463.7±14.963.9±14.6<0.001
 men (%)55.95555.40.03
 body mass index (kg/m2)27.0 (23.1–32.3)27.8 (23.7–33.3)27.9 (23.9–33.4)<0.001
 race (%)<0.001
  white62.974.773.9
  black31.621.920.8
  other5.63.55.4
 any insurance coverage (%)92.193.393.0<0.001
 employment (%)<0.001
  unemployed44.544.945.8
  employed15.413.112.5
  retired40.142.041.7
 distance to dialysis unit (miles)
  hemodialysis4.2 (<2.0–7.7)4.7 (<2.0–14)18.4 (10.1–29.0)<0.001
  peritoneal dialysis7.3 (3.8–13.1)22.1 (8.3–37.1)36.0 (23.8–54.0)<0.001
Kidney disease
 primary disease causing ESRD (%)<0.001
  diabetes mellitus45.447.648.0
  hypertension28.827.727.2
  GN6.86.35.9
  cystic disease2.12.22.1
  other16.916.216.8
 modality as peritoneal dialysis (%)
  at initiation5.76.37.9<0.001
  at 90 d5.96.88.4<0.001
 estimated GFR (ml/min per 1.73 m2)9.9 (7.2–13.2)10.2 (7.5–13.5)10.1 (7.4–13.3)<0.001
Medical comorbid conditions (%)
 congestive heart failure33.236.135.2<0.001
 heart disease (includes valvular)32.237.937.9<0.001
 stroke9.510.611.1<0.001
 hypertension84.285.485.2<0.001
 diabetes mellitus52.556.556.6<0.001
 chronic obstructive pulmonary disease8.411.912.0<0.001
 cancer7.27.88.3<0.001
 assistance with activities of daily living13.015.215.0<0.001
 institutionalized (nursing home)6.87.87.7<0.001
 tobacco use5.97.98.5<0.001
 alcohol use1.51.61.50.45
 illicit drug use1.51.00.8<0.001
ZIP code–based measures of community socioeconomic status
 household income ($ thousands)40.2 (31.8–51.4)33.0 (29.3–37.9)30.6 (26.8–35.3)<0.001
 high school diploma (% of residents)77.3±13.375.4±9.972.5±10.5<0.001
  • Statistical testing performed by Pearson chi-squared test for categorical variables and Kruskal-Wallis test for continuous variables. Values expressed with a plus/minus sign are means ± SDs. Values expressed with a range are medians (25th–75th percentile interquartile ranges). Percentages may not add to 100% because of rounding. Estimates of ZIP code income and education are based on calculations from the U.S. Census, 2000.