Table 1 Demographics, Socioeconomic Status, and Behavioral Characteristics by Income Levels from NHANES III (1988–1994)
Characteristics | Total (N = 7817) | Low Income (N = 3420) | Middle Income (N = 3014) | High Income (N = 1383) | P-value |
|---|---|---|---|---|---|
Age (years) |  |  |  |  | < 0.001a |
 Median (Range) | 53 (40–89) | 58 (40–89) | 53 (40–89) | 51 (40–89) |  |
 Younger than 55 yrs | 51.6% | 40.7% | 52.0% | 61.0% |  |
 55 yrs. or older | 48.4% | 59.3% | 48.0% | 39.0% |  |
Race/Ethnicity |  |  |  |  | < 0.001a |
 White | 79.0% | 64.1% | 80.5% | 90.5% |  |
 Black | 9.8% | 17.7% | 8.7% | 4.2% |  |
 Hispanics/Other | 11.1% | 18.2% | 10.7% | 5.3% |  |
Gender |  |  |  |  | < 0.001a |
 Male | 47.6% | 42.3% | 47.3% | 52.8% |  |
 Female | 52.4% | 57.7% | 52.7% | 47.2% |  |
Education |  |  |  |  | < 0.001a |
 Below High School | 29.1% | 55.6% | 29.6% | 14.8% |  |
 High School/Equivalent | 32.5% | 27.1% | 36.6% | 26.2% |  |
 Above High School | 38.4% | 7.9% | 29.2% | 62.9% |  |
Occupation |  |  |  |  | < 0.001a |
 Not Working | 2.8% | 5.3% | 2.4% | 1.1% |  |
 White Collar and Professional | 26.7% | 11.7% | 23.5% | 45.0% |  |
 White Collar, Semi-Routine | 22.8% | 15.6% | 23.7% | 27.9% |  |
 Blue Collar, High Skill | 13.3% | 14.3% | 15.1% | 9.6% |  |
 Blue Collar, Semi-Routine | 34.5% | 53.1% | 35.3% | 16.4% |  |
Body Mass Index (kg/m2) | Â | Â | Â | Â | 0.001a |
 Median (Range) | 26.6 (11.7–67.3) | 27.3 (13.3–60.0) | 26.5 (11.7–67.3) | 25.9 (15.9–55.9) |  |
 Underweight | 1.6% | 2.2% | 1.5% | 1.0% |  |
 Normal | 34.5% | 31.3% | 35.0% | 36.6% |  |
 Overweight | 37.1% | 34.3% | 37.2% | 39.5% |  |
 Obese | 26.9% | 32.2% | 26.4% | 22.8% |  |
Smoking |  |  |  |  | < 0.001a |
 Never | 42.2% | 41.8% | 43.2% | 41.0% |  |
 Former | 33.9% | 28.9% | 33.4% | 39.3% |  |
 Current | 23.9% | 29.4% | 23.4% | 19.7% |  |
Physical Activityb |  |  |  |  | < 0.001a |
 More Active | 37.7% | 28.4% | 37.9% | 45.8% |  |
 Less Active | 21.6% | 27.8% | 20.5% | 17.5% |  |
 About Same | 40.7% | 43.8% | 41.6% | 36.7% |  |
C-Reactive Protein |  |  |  |  | < 0.001a |
 Mean (Range) | 0.45 (0.21–9.79) | 0.57 (0.21–9.79) | 0.43 (0.21–8.90) | 0.38 (0.21–9.20) |  |
  < 0.22 mg/dL | 66.1% | 56.0% | 67.9% | 72.8% |  |
 0.22–0.99 mg/dL | 24.7% | 30.7% | 23.7% | 20.7% |  |
  > 0.99 mg/dL | 9.2% | 13.3% | 8.4% | 6.5% |  |
Fibrinogen |  |  |  |  | < 0.001c |
 Mean (Range) | 303 (19–957) | 319 (30–928) | 298 (19–957) | 294 (85–806) |  |