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. 2015 Mar 1;181(6):385–396. doi: 10.1093/aje/kwu316

Table 1.

Baseline Characteristics of the Study Population According to Socioeconomic Status, National Health and Nutrition Examination Survey, 2007–2008 and 2009–2010a

Characteristic Total (n = 9,823)
Socioeconomic Statusb
P Value
Low (n = 3,289)
Medium (n = 3,262)
High (n = 3,272)
% Median (IQR) % Median (IQR) % Median (IQR) % Median (IQR)
Age, years 49 (35–64) 44 (31–61) 51 (36–68) 51 (38–63) <0.001
Male sex 49.0 44.5 49.9 52.7 <0.001
Race/ethnicity <0.001
 Non-Hispanic white 50.1 39.9 46.7 63.5
 Non-Hispanic black 18.0 17.9 20.2 15.9
 Mexican-American 17.2 24.2 18.8 8.5
 Otherc 14.7 17.9 14.3 12.1
Less than high school education 35.1 55.1 34.2 10.8 <0.001
Current smokingd 22.1 32.9 19.1 14.3 <0.001
High alcohol intakee 20.4 26.3 21.1 14.7 <0.001
Physical inactivityf 53.4 67.3 57.8 41.2 <0.001
Unhealthy dietg 76.7 82.5 79.3 72.4 <0.001
Sedentary time ≥4 hours/day 32 41 33 24 <0.001
Obesityh 40.6 46.9 41.5 35.8 <0.001
Abdominal obesityi 51 58.7 51.9 40.5 <0.001
Hypertension 21.2 23.3 23.1 18.4 <0.001
Diabetes mellitus 14.6 17.4 15.1 11.5 <0.001
Hypercholesterolemia, ≥6.2 mmol/L 14.3 14.4 14.8 13.6 0.04
Health insurance 23.5 39.3 23.9 7.3 <0.001
No health-care visits in last year 15.9 21.5 16.2 9.2 <0.001
Serum creatinine level, mg/dL 0.84 (0.72–1.01) 0.82 (0.69–0.96) 0.83 (0.72–1.02) 0.88 (0.74–1.02) 0.006
eGFR, mL/minute/1.73 m2 95.7 (78.4–111.1) 92.6 (77.1–106.4) 95.3 (75.5–111.6) 101.5 (83.9–115.9 <0.001
Low eGFR, <60 mL/minute/1.73 m2 9.2 8.7 7.7 <0.001
Albumin:creatinine ratio, mg/g 7.0 (4.5–13.6) 7.7 (4.7–6.1) 7.2 (4.5–14.4) 6.3 (4.2–10.9) <0.001
Moderate albuminuria, ≥30 mg/g 12.1 13.1 9.2 <0.001
Chronic kidney disease 18.4 17.5 14.8 <0.001

Abbreviations: eGFR, estimated glomerular filtration rate; IQR, interquartile range.

a There was no significant difference in age and sex between the participants who were excluded because of missing income information and the final study participants.

b Socioeconomic status was defined as tertile of poverty income ratio (≤1.36 (low), 1.37–3.29 (middle), or 3.30–5.00 (high)). The poverty income ratio is calculated by dividing household income by the US federal poverty threshold.

c “Other” included other Hispanics as well as persons of other ethnicities, including multiracial individuals.

d Having smoked ≥100 cigarettes in one's lifetime and smoking every day or on some days of the week at the time of the interview.

e Having consumed ≥20 alcoholic drinks per month in the previous 12 months.

f Engaging in moderate-to-vigorous recreational physical activity less than 3 times per week.

g Consuming fruits or vegetables fewer than 5 times per week or reporting that fruits or vegetables were never or rarely available at home.

h Body mass index (weight (kg)/height (m)2) ≥30.

i Waist circumference ≥88 cm in women and ≥102 cm in men.