Table 1.
Characteristics of the study population by quartiles of toenail Cd concentrations: the CARDIA study
| Characteristics | Quartiles of toenail Cd concentrations | Total | P value | |||
|---|---|---|---|---|---|---|
| Q1 (lowest) | Q2 | Q3 | Q4 (highest) | |||
| n | 613 | 613 | 609 | 611 | 2446 | – |
| Median Cd level (ppb) | 2.9 (2.3–3.6) | 6.0 (5.1–7.1) | 11.7 (9.9–14.4) | 41.0 (25.9–87.2) | 8.2 (4.3–18.6) | – |
| Age at Y25 (year) | 50.5 ± 3.5 | 50.3 ± 3.6 | 49.9 ± 3.7 | 49.7 ± 3.7 | 50.1 ± 3.6 | < 0.01 |
| Female (%) | 51.1 | 61.3 | 59.1 | 58.9 | 57.6 | < 0.01 |
| Black (%) | 40.5 | 45.0 | 52.6 | 51.6 | 47.4 | < 0.01 |
| Education levels at Y25 (year) | 15.5 ± 2.6 | 15.4 ± 2.7 | 14.9 ± 2.6 | 14.8 ± 2.7 | 15.1 ± 2.7 | < 0.01 |
| Smoking status at Y2 (%) | 0.36 | |||||
| Never smoker | 62.3 | 62.8 | 63.2 | 59.7 | 62.0 | |
| Former smoker | 15.7 | 13.5 | 12.2 | 13.5 | 13.7 | |
| Current smoker | 22.0 | 23.7 | 24.6 | 26.8 | 24.3 | |
| Alcohol consumption (mL/day) | 7.2 ± 9.6 | 8.2 ± 12.0 | 8.4 ± 11.3 | 8.0 ± 11.0 | 7.9 ± 11.0 | 0.59 |
| Physical activity (exercise unit) | 361 ± 218 | 347 ± 217 | 344 ± 229 | 347 ± 214 | 350 ± 220 | 0.29 |
| BMI at Y2 (kg/m2) | 25.0 ± 5.3 | 25.4 ± 5.3 | 25.4 ± 5.5 | 25.4 ± 5.2 | 25.3 ± 5.3 | 0.49 |
| Systolic blood pressure at Y2 (mmHg) | 107.17 ± 10.27 | 107.01 ± 10.77 | 107.47 ± 10.38 | 107.42 ± 9.97 | 107.27 ± 10.35 | 0.85 |
| Diastolic blood pressure at Y2 (mmHg) | 67.8 ± 9.1 | 67.4 ± 9.7 | 67.1 ± 9.1 | 66.7 ± 9.5 | 67.3 ± 9.3 | 0.25 |
| Total cholesterol at Y2 (mg/dL) | 183.5 ± 33.1 | 185.0 ± 36.8 | 184.1 ± 34.7 | 184.6 ± 36.1 | 184.3 ± 35.2 | 0.89 |
| HDL-cholesterol at Y2 (mg/dL) | 53.6 ± 13.3 | 55.1 ± 14.1 | 55.2 ± 13.9 | 55.5 ± 15.0 | 54.9 ± 14.1 | 0.10 |
| LDL-cholesterol at Y2 (mg/dL) | 114.3 ± 31.7 | 114.2 ± 34.1 | 113.8 ± 32.8 | 114.2 ± 33.7 | 114.1 ± 33.1 | 0.993 |
| Triglycerides at Y2 (mg/dL) | 78.4 ± 50.6 | 79.2 ± 56.2 | 78.0 ± 65.1 | 75.6 ± 44.9 | 77.8 ± 54.7 | 0.82 |
| Glucose at Y0 (mg/dL) | 82.3 ± 13.8 | 82.1 ± 9.7 | 82.1 ± 13.0 | 81.2 ± 7.8 | 81.9 ± 11.3 | 0.34 |
| Insulin at Y0 (uU/mL) | 7.83 ± 3.47 | 8.15 ± 3.78 | 7.96 ± 3.54 | 8.12 ± 3.72 | 8.02 ± 3.63 | 0.49 |
The results are presented by means ± standard deviations, medians (inter-quarter ranges), or proportions
P values are for any difference across quartiles of toenail Cd levels by using analysis of variance, Kruskal–Wallis test, or chi-squared test, as appropriate
BMI Body mass index, CARDIA coronary artery risk development in young adults, Cd cadmium HDL high-density lipoproteins, LDL low-density lipoproteins Q, quartile, Y CARDIA exam year