Table 1.
Baseline characteristics of participants by quartile of pyridoxal 5′-phosphate (PLP) (NHANES 2005–2008).
| Characteristics | Quartiles Plasma Pyridoxal 5′-Phosphate (PLP) (nmol/L) | p-Value | |||
|---|---|---|---|---|---|
| Q1 (<26.4) | Q2 (26.4–43.4) | Q3 (43.4–74.8) | Q4 (≥74.8) | ||
| n = 3804 | n = 3815 | n = 3790 | n = 3797 | ||
| Gender (%) a | |||||
| Male | 1533 (37.63) | 1891 (48.66) | 2209 (57.24) | 2120 (53.65) | <0.001 |
| Female | 2271 (62.37) | 1924 (51.33) | 1581 (42.76) | 1677 (46.35) | |
| Age (%) a | |||||
| 18–39 years | 1125 (31.83) | 1579 (42.66) | 1630 (43.01) | 1351 (37.15) | <0.001 |
| 40–59 years | 1222 (40.39) | 1212 (38.60) | 1157 (37.70) | 1103 (36.62) | |
| ≥60 year | 1457 (27.76) | 1024 (18.74) | 1003 (19.28) | 1343 (26.23) | |
| Race/ethnicity (%) a | |||||
| Mexican American | 610 (7.22) | 828 (10.00) | 836 (9.87) | 598 (6.43) | |
| Other Hispanic | 286 (3.83) | 372 (5.45) | 349 (4.98) | 294 (3.91) | |
| Non-Hispanic White | 1724 (67.54) | 1610 (65.17) | 1723 (69.11) | 2115 (76.13) | <0.001 |
| Non-Hispanic Black | 1058 (16.83) | 817 (12.33) | 683 (9.53) | 602 (7.45) | |
| Other races | 126 (4.58) | 188 (7.05) | 199 (6.51) | 188 (6.08) | |
| Educational level (%) a | |||||
| <high school | 1379 (25.26) | 1254 (22.43) | 1075 (18.57) | 814 (13.05) | <0.001 |
| High school | 1031 (29.87) | 932 (24.94) | 914 (24.18) | 816 (20.76) | |
| >high school | 1386 (44.87) | 1627 (52.63) | 1796 (57.26) | 2163 (66.19) | |
| Ratio of income to poverty (%) a | |||||
| <1 | 959 (18.21) | 808 (14.15) | 695 (11.92) | 503 (7.86) | <0.001 |
| ≥1 | 2845 (81.79) | 3007 (85.84) | 3095 (88.08) | 3294 (92.14) | |
| Marital status (%) a | |||||
| Married/Cohabiting | 1983 (58.91) | 2158 (63.91 | 2218 (66.19) | 2263 (66.23) | <0.001 |
| Windowed/Living alone | 1741 (41.09) | 1514 (36.09) | 1394 (33.81) | 1410 (33.77) | |
| Body mass index (%) a | |||||
| <25 kg/m2 | 971 (26.81) | 1098 (30.02) | 1204 (32.93) | 1371 (38.88) | <0.001 |
| 25 to <30 kg/m2 | 1026 (25.37) | 1218 (31.40) | 1372 (35.88) | 1430 (37.37) | |
| ≥30 kg/m2 | 1807 (47.81) | 1499 (38.58) | 1214 (31.20) | 996 (23.75) | |
| Physical activity (%) a | |||||
| Vigorous | 882 (26.80) | 1284 (37.29) | 1536 (44.33) | 1588 (45.78) | <0.001 |
| Moderate | 1142 (32.22) | 1080 (29.83) | 1086 (30.72) | 1197 (32.61) | |
| Other | 1780 (40.98) | 1450 (32.88) | 1168 (24.95) | 1012 (21.61) | |
| Depressive symptoms (%) a | 397 (10.95) | 279 (6.68) | 201 (4.85) | 179 (3.50) | <0.001 |
| Diabetes (%) a | 861 (18.52) | 616 (11.78) | 505 (10.20) | 492 (9.21) | <0.001 |
| Hypertension (%) a | 2194 (53.96) | 1786 (44.11) | 1726 (44.24) | 1847 (45.17) | <0.001 |
| Caffeine intake (mg/d) b | 103 (212) | 94 (172) | 86 (152) | 96.5 (173) | <0.001 |
| Total energy (kcal/day) b | 1772.5 (180.5) | 1891.5 (166) | 2591 (164) | 1977 (188) | <0.001 |
| Smoke at least 100 cigarettes in life (%) a | 2020 (56.11) | 1677 (48.63) | 1513 (44.21) | 1485 (40.02) | <0.001 |
| Had at least 12 alcohol drinks a year (%) a | 2133 (68.03) | 2261 (75.85) | 2387 (78.23) | 2539 (79.51) | <0.001 |
| Sampling season (%) a | |||||
| November to April | 1825 (42.90) | 1824 (40.04) | 1697 (39.29) | 1595 (37.30) | 0.081 |
| May to October | 1979 (57.10) | 1991 (59.96) | 2093 (60.71) | 2202 (62.70) | |
Data are represented the number of subjects (weighted percentage) or median (interquartile range). a Chi-square test was used to compare the percentages between participants in different quartiles of serum PLP concentrations. b Kruskal–Wallis test were used to compare the medians between participants in different quartiles of serum PLP concentrations.