Table 1.

Baseline characteristics of the study participants in health examinations of the National Health Insurance Service of the Republic of Korea from 2012 to 2016

VariablesMatched Controls, n=408,873Predialysis CKD, n=408,873
Matched and adjusted variables
 Age, yr65 [56–72]65 [56–72]
 Men208,181 (51)208,181 (51)
 Low incomea89,541 (22)89,541 (22)
 Smoking history
  Never266,213 (65)266,213 (65)
  Previous78,438 (19)78,438 (19)
  Current64,222 (16)64,222 (16)
Unmatched but adjusted variables
 Body mass index, kg/m223.8 [21.8–25.8]24.6 [22.5–27.0]
 Place of residence
  Urban175,445 (43)182,642 (45)
  Rural233,428 (57)226,231 (55)
 Previous immunosuppressant usage77,316 (19)78,575 (19)
 Comorbidities
  Hypertension177,336 (43)277,032 (68)
  Diabetes mellitus61,186 (15)135,305 (33)
  Congestive heart failure7780 (2)19,759 (5)
  Dementia11,764 (3)15,346 (4)
  Peripheral vascular disease43,406 (11)59,963 (15)
  Cancer19,562 (5)24,795 (6)
  Liver disease5227 (1)8431 (2)
  Chronic obstructive pulmonary disease78,327 (19)87,427 (21)
Unadjusted variables
 Creatinine, mg/dl0.8 [0.7–1.0]1.2 [1.0–1.4]
 eGFR, ml/min per 1.73 m286 [74–98]55 [48–59]
 Dipstick albuminuria
  None or trace408,873 (100)277,544 (68)
  1+0 (0)69,817 (17)
  ≥2+0 (0)61,512 (15)
  • a Low income was defined as a total income <20th percentile for the nation.