Association between exposure to ambient air pollution and renal function in Korean adults

Table 1 Characteristics of the study subjects (n = 24,407)

Characteristics	Mean ± SD or N (%)	Missing
Age (years)	52.8 ± 14.3	0
Female gender	13,933 (57.1)	0
Education level		299
≤ Elementary school	7425 (30.8)
Middle school	3020 (12.5)
High school	7484 (31.0)
≥ College or graduate school	6179 (25.6)
Smoking		250
Never	14,012 (58.0)
Former-smokers	5023 (20.8)
Current-smokers	5122 (21.2)
Alcohol Consumption (per month)		313
Never	7382 (30.6)
≤ 1	6659 (27.6)
2–3	8108 (33.7)
≥ 4	1945 (8.1)
Daily protein intake (g)	66.0 (36.3)	2725
Residential region		0
Urban	15,881 (65.1)
Rural	8526 (34.9)
WC (cm)	82.1 ± 9.6	132
BMI (kg/m²)	23.8 ± 3.2	128
SBP (mm Hg)	120.5 ± 17.8	19
DBP (mm Hg)	77.1 ± 10.7	19
Hypertension^a	8299 (34.0)
Fasting Glucose (mg/dL)	99.1 ± 24.3	43
Diabetes^b	2635 (10.8)
Total cholesterol (mg/dL)	190.8 ± 36.4	50
Creatinine (mg/dL)	0.9 ± 0.2	0
eGFR mL/min/1.73 m^2c	84.4 ± 17.1
CKD^c	1361 (5.6)

BMI body mass index, WC waist circumference, SBP systolic blood pressure, DBP diastolic blood pressure, eGFR estimated glomerular filtration rate, CKD chronic kidney disease
^aHypertension was defined as a systolic blood pressure ≥ 140 mmHg or a diastolic blood pressure ≥ 90 mmHg or taking hypertension treatment medication more than 20 days a month
^bDiabetes was defined as fasting glucose ≥126 mg/dL or taking diabetes treatment medication or taking insulin by injection or physician diagnose
^ceGFR was calculated by MDRD-4 equation (GFR in mL/min per 1.73 m² = 175 x SerumCr-1.154 x age-0.203 × 1.212 (if patient is black) × 0.742 (if female))
^cCKD was defined as eGFR < 60 mL/min/1.73 m²

ISSN: 2052-4374