Table 1.
Baseline characteristics of the study population by quintiles of folate intake: the CARDIA study, 1985–2015*†
| Characteristics | Black men and women (n = 2,412) | White men and women (n = 2,291) | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Q1 | Q2 | Q3 | Q4 | Q5 | P value | Q1 | Q2 | Q3 | Q4 | Q5 | P value | |
| n = 620 | n = 528 | n = 467 | n = 427 | n = 370 | n = 320 | n = 413 | n = 474 | n = 514 | n = 570 | |||
| Range (µg/day) | <281.6 | 281.6–393.4 | 393.4–508.4 | 508.4–694.0 | ≥694.0 | NA | <281.6 | 281.6–393.5 | 393.5–508.6 | 508.6–693.5 | ≥693.5 | NA |
| Median level (µg/day) | 212.5 | 336.3 | 449.2 | 584.5 | 877.0 | NA | 221.8 | 341.8 | 451.3 | 595.6 | 889.2 | NA |
| Total energy (kcal/day) | 1,996.6 ± 687.8 |
2,687.4 ± 878.6 |
3,253.9 ± 1,259.1 |
3,512.1 ± 1,400.5 |
3,818.8 ± 1,470.6 |
<0.05 | 1,930.9 ± 613.9 |
2,354.4 ± 711.4 |
2,565.1 ± 841.5 |
2,812.6 ± 1,011.4 |
3,096.6 ± 1,173.7 |
<0.05 |
| A Priori Diet Quality Score | 54.0 ± 7.8 | 55.9 ± 9.0 | 56.2 ± 8.9 | 58.4 ± 9.2 | 60.1 ± 9.6 | <0.05 | 59.7 ± 9.5 | 64.8 ± 9.4 | 66.5 ± 9.9 | 68.1 ± 9.9 | 71.3 ± 9.8 | <0.05 |
| Age at baseline (years) | 24.4 ± 3.9 | 24.3 ± 3.8 | 23.9 ± 3.9 | 24.6 ± 3.8 | 24.6 ± 3.5 | <0.05 | 25.0 ± 3.5 | 25.4 ± 3.4 | 25.5 ± 3.4 | 25.5 ± 3.3 | 25.7 ± 3.3 | <0.05 |
| Female (%) | 70.3 | 57.0 | 45.0 | 46.1 | 45.1 | <0.05 | 66.3 | 50.1 | 46.6 | 44.6 | 48.4 | <0.05 |
| Education (years) | 13.7 ± 2.3 | 13.8 ± 2.3 | 14.0 ± 4.6 | 13.9 ± 2.6 | 14.1 ± 2.4 | 0.21 | 14.6 ± 2.8 | 15.4 ± 2.7 | 15.8 ± 2.6 | 15.8 ± 2.7 | 15.9 ± 2.7 | <0.05 |
| Smokers (%) | 0.44 | <0.05 | ||||||||||
| Never | 58.6 | 56.1 | 61.0 | 55.0 | 57.5 | 44.8 | 57.5 | 60.3 | 59.0 | 61.3 | ||
| Former | 15.1 | 15.7 | 12.2 | 13.2 | 15.3 | 24.1 | 23.0 | 26.7 | 27.2 | 26.8 | ||
| Current | 26.3 | 28.2 | 26.9 | 31.8 | 27.1 | 31.0 | 19.6 | 13.0 | 13.9 | 11.9 | ||
| Alcohol consumption (mL/day) | 2.0 (0, 8.3) | 4.4 (0.3, 15.1) | 4.8 (0.3, 16.2) | 6.2 (0.8, 17.9) | 4.2 (0.5, 16.7) | <0.05 | 4.1 (0.7, 10.9) | 8.2 (2.4, 16.0) | 6.7 (1.3, 16.7) | 8.5 (2.5, 20.2) | 8.5 (2.4, 19.1) | <0.05 |
| Physical activity (EU) | 211.0(125.5,324.2) | 238.9(152.6,425.2) | 335.4(193.5,527.3) | 350.0(215.6,527.6) | 392.9(263.7,606.0) | <0.05 | 276.8(185.8,407.7) | 315.8(211.3,442.4) | 348.2(238.1,514.0) | 383.3(253.0,531.8) | 436.3(304.0,597.7) | <0.05 |
| BMI (kg/m2) | 28.9 ± 7.0 | 28.1 ± 6.7 | 27.7 ± 5.9 | 27.9 ± 6.3 | 27.2 ± 5.7 | <0.05 | 26.2 ± 5.4 | 26.1 ± 4.9 | 26.0 ± 4.9 | 25.8 ± 4.5 | 25.1 ± 4.5 | <0.05 |
| Glucose at baseline (mmol/L) | 4.49 ± 0.46 | 4.50 ± 0.50 | 4.49 ± 0.46 | 4.53 ± 0.46 | 4.50 ± 0.46 | 0.62 | 4.58 ± 0.47 | 4.58 ± 0.46 | 4.57 ± 0.46 | 4.63 ± 0.46 | 4.59 ± 0.41 | 0.32 |
| SBP (pascal) | 0.85 ± 0.08 | 0.85 ± 0.07 | 0.85 ± 0.07 | 0.86 ± 0.08 | 0.85 ± 0.07 | 0.17 | 0.82 ± 0.08 | 0.82 ± 0.07 | 0.82 ± 0.07 | 0.82 ± 0.07 | 0.82 ± 0.07 | 0.92 |
| DBP (pascal) | 0.54 ± 0.07 | 0.54 ± 0.06 | 0.54 ± 0.06 | 0.54 ± 0.06 | 0.54 ± 0.06 | 0.78 | 0.52 ± 0.06 | 0.52 ± 0.06 | 0.52 ± 0.06 | 0.52 ± 0.05 | 0.52 ± 0.05 | 0.24 |
| HDL-c–to–LDL-c ratio | 0.55 ± 0.24 | 0.56 ± 0.29 | 0.55 ± 0.23 | 0.56 ± 0.25 | 0.58 ± 0.28 | 0.23 | 0.51 ± 0.31 | 0.49 ± 0.21 | 0.51 ± 0.25 | 0.51 ± 0.21 | 0.56 ± 0.26 | <0.05 |
| TG (mmol/L) | 0.88 ± 0.46 | 0.90 ± 0.43 | 0.90 ± 0.46 | 0.95 ± 0.47 | 0.92 ± 0.47 | <0.05 | 1.10 ± 0.68 | 1.16 ± 0.73 | 1.12 ± 0.68 | 1.15 ± 0.71 | 1.07 ± 0.68 | <0.05 |
| Family history of diabetes (yes, %) | 20.7 | 16.7 | 17.8 | 15.9 | 11.4 | <0.05 | 12.8 | 12.8 | 9.9 | 9.1 | 9.8 | 0.24 |
| Folic acid supplement use (yes, %) | 28.2 | 47.2 | 52.9 | 62.8 | 74.1 | <0.05 | 31.3 | 49.6 | 69.0 | 75.3 | 87.0 | <0.05 |
DBP, diastolic blood pressure; EU, exercise units; NA, not applicable; Q, quintile; SBP, systolic blood pressure.
*
Results were presented as means ± SDs, medians (interquartile ranges), or proportions. All mean or median values, if not specified, were based on the values of cumulative averages by the time of incident diabetes, last follow-up, death, or data freeze, whichever came first.
†
P values are for any differences across quintiles of folate intake (ANOVA, Kruskal-Wallis test, or χ2 test, as appropriate).