TABLE 1.
1988–1994 |
1999–2010 |
1988–1994 |
1999–2010 |
|||||
n | Serum folate | n | Serum folate | n | RBC folate | n | RBC folate | |
nmol/L | nmol/L | nmol/L | nmol/L | |||||
Total | 23,359 | 16.7 ± 0.5 | 46,873 | 41.0 ± 0.3 | 22,846 | 747 ± 10 | 46,759 | 1120 ± 7 |
Age group | ||||||||
4–11 y | 4627 | 29.6 ± 0.7 | 7379 | 56.1 ± 0.4 | 4498 | 851 ± 16 | 7380 | 1130 ± 7 |
12–19 y | 2956 | 15.5 ± 0.6 | 10,614 | 39.5 ± 0.4 | 2888 | 642 ± 12 | 10,574 | 971 ± 8 |
20–39 y | 6467 | 13.0 ± 0.4 | 10,044 | 35.1 ± 0.3 | 6335 | 674 ± 9 | 10,017 | 1020 ± 7 |
40–59 y | 4258 | 15.5 ± 0.5 | 8966 | 38.9 ± 0.4 | 4180 | 763 ± 13 | 8945 | 1150 ± 10 |
60–79 y | 3882 | 22.0 ± 0.6 | 7739 | 49.0 ± 0.5 | 3796 | 898 ± 15 | 7718 | 1350 ± 11 |
≥80 y | 1169 | 26.2 ± 1.0 | 2131 | 57.8 ± 1.0 | 1149 | 965 ± 22 | 2125 | 1490 ± 19 |
P2 | <0.001 | <0.001 | <0.001 | <0.001 | ||||
P-model 12,3 | <0.001 | <0.001 | <0.001 | <0.001 | ||||
P-model 22,4 | <0.001 | <0.001 | <0.001 | <0.001 | ||||
Gender | ||||||||
Male | 11,130 | 15.8 ± 0.5 | 23,021 | 38.9 ± 0.3 | 10,877 | 734 ± 9 | 22,966 | 1090 ± 8 |
Female | 12,229 | 17.7 ± 0.5 | 23,852 | 43.2 ± 0.3 | 11,969 | 759 ± 12 | 23,793 | 1150 ± 8 |
Age 15–44 y | 5254 | 14.0 ± 0.5 | 9994 | 37.6 ± 0.3 | 5153 | 686 ± 12 | 9968 | 1060 ± 9 |
P5 | <0.001 | <0.001 | 0.001 | <0.001 | ||||
P-model 13,5 | <0.001 | <0.001 | 0.001 | <0.001 | ||||
P-model 24,5 | 0.008 | <0.001 | 0.982 | <0.001 | ||||
Race/ethnicity | ||||||||
MA | 7017 | 15.0 ± 0.5 | 11,822 | 37.4 ± 0.4 | 6820 | 696 ± 15 | 11,801 | 1020 ± 10 |
NHW | 8533 | 17.5 ± 0.6 | 19,241 | 43.1 ± 0.4 | 8344 | 786 ± 12 | 19,171 | 1190 ± 10 |
NHB | 6813 | 13.1 ± 0.3 | 10,722 | 34.3 ± 0.3 | 6695 | 573 ± 6 | 10,703 | 900 ± 5 |
P6 | <0.001 | <0.001 | <0.001 | <0.001 | ||||
P-model 13,6 | <0.001 | <0.001 | <0.001 | <0.001 | ||||
P-model 24,6 | <0.001 | <0.001 | <0.001 | <0.001 | ||||
PIR | ||||||||
<1.0 | 6154 | 15.6 ± 0.6 | 10,772 | 37.7 ± 0.4 | 6009 | 687 ± 14 | 10,753 | 1020 ± 10 |
1.0–1.9 | 5909 | 15.8 ± 0.5 | 11,690 | 39.6 ± 0.3 | 5785 | 703 ± 12 | 11,656 | 1080 ± 9 |
2.0–3.9 | 6462 | 16.8 ± 0.5 | 11,318 | 41.4 ± 0.4 | 6299 | 758 ± 11 | 11,290 | 1130 ± 9 |
≥4.0 | 2756 | 19.0 ± 0.8 | 9520 | 43.3 ± 0.5 | 2707 | 830 ± 13 | 9488 | 1190 ± 10 |
P7 | <0.001 | <0.001 | <0.001 | <0.001 | ||||
P-model 13,7 | <0.001 | <0.001 | <0.001 | <0.001 | ||||
P-model 24,7 | 0.004 | <0.001 | 0.001 | <0.001 | ||||
Supplement use8 | ||||||||
Yes | 7949 | 24.3 ± 0.7 | 15,294 | 49.9 ± 0.4 | 7776 | 923 ± 14 | 15,211 | 1320 ± 10 |
No | 15,376 | 13.1 ± 0.3 | 23,356 | 35.4 ± 0.3 | 15,038 | 649 ± 7 | 23,287 | 994 ± 7 |
P9 | <0.001 | <0.001 | <0.001 | <0.001 | ||||
P-model 13,9 | NA | NA | NA | NA | ||||
P-model 24,9 | <0.001 | <0.001 | <0.001 | <0.001 | ||||
Survey period | ||||||||
1999–2000 | NA | 7411 | 45.8 ± 1.0 | NA | 7393 | 1180 ± 24 | ||
2001–2002 | NA | 8242 | 42.7 ± 0.6 | NA | 8220 | 1160 ± 17 | ||
2003–2004 | NA | 7692 | 40.3 ± 0.7 | NA | 7618 | 1080 ± 16 | ||
2005–2006 | NA | 7639 | 41.1 ± 0.7 | NA | 7578 | 1140 ± 11 | ||
2007–2008 | NA | 7705 | 39.2 ± 0.9 | NA | 7728 | 1120 ± 23 | ||
2009–2010 | NA | 8184 | 37.9 ± 0.5 | NA | 8222 | 1040 ± 14 | ||
P10 | NA | <0.001 | NA | <0.001 | ||||
P-model 13,10 | NA | <0.001 | NA | <0.001 | ||||
P-model 24,10 | NA | <0.001 | NA | <0.001 |
Values are geometric means ± SE. Serum and RBC folate concentrations were measured from 1988–2006 by the Bio-Rad radioassay and assay-adjusted to be comparable to the microbiologic assay that was used from 2007–2010 (13, 16, 17). MA, Mexican American; NHB, non-Hispanic black; NHW, non-Hispanic white; NA, not applicable; PIR, poverty-to-income ratio.
Test comparing group means across age categories.
-value for multiple linear regression model 1 including age, gender, race/ethnicity, and PIR for prefortification data and age, gender, race/ethnicity, PIR, and survey period for postfortification data (1999–2010).
value for multiple linear regression model 2 including age, gender, race/ethnicity, PIR, and supplement use for prefortification data and age, gender, race/ethnicity, PIR, supplement use, and survey period for postfortification data (1999–2008).
Test comparing males and females.
Test comparing group means across race/ethnicity categories.
Test of linear trend across PIR categories.
Geometric means by dietary supplement use were limited to data from 1999–2008 for the postfortification period.
Test comparing group means across supplement use categories.
Test of linear trend across survey periods.