Figure 1
Interactions between blood lead levels and micronutrients (A, folate; B, vitamin B6; and C, vitamin B12) on hyperhomocysteinemia. Odds ratios were adjusted for age, sex, race/ethnicity, poverty income ratio, BMI, smoking, alcohol, and physical activity. Subjects with the lowest quartile of blood lead and each micronutrient (A, folate; B, vitamin B6; and C, vitamin B12) less than the median were used as a reference.
Q1: first quartile; Q2: second quartile; Q3: third quartile; Q4: fourth quartile.
Table 1.General characteristics of the all study subjects according to the categories of blood lead
Characteristics |
Quartiles of blood lead levels
|
p-trend |
Total (n = 4089) |
Q1 (n = 971) |
Q2 (n = 1100) |
Q3 (n = 1001) |
Q4
|
Q4-1 (n = 252) |
Q4-2 (n = 242) |
Q4-3 (n = 270) |
Q4-4 (n = 253) |
Mean±standard deviation |
|
|
|
|
|
|
|
|
|
Blood lead (μg/dL) |
2.1±1.8 (0.2-33.0) |
0.8±0.2 (0.2-1.0) |
1.3±0.2 (1.1-1.6) |
2.1±0.3 (1.7-2.5) |
2.7±0.1 (2.6-2.9) |
3.2±0.1 (3.0-3.4) |
3.9±0.3 (3.5-4.5) |
7.2±3.7 (4.6-33.0) |
|
Age (y) |
50.4±19.3 |
38.7±16.9 |
48.1±18.4 |
55.3±17.7 |
56.4±17.3 |
61.3±17.0 |
59.5±18.0 |
59.7±18.5 |
<0.001 |
Body mass index (kg/m2) |
28.4±6.2 |
29.1±7.6 |
28.5±5.9 |
28.7±5.8 |
27.8±5.6 |
27.5±4.6 |
27.2±5.2 |
27.4±5.3 |
<0.001 |
Poverty income ratio |
2.6±1.6 |
2.7±1.6 |
2.7±1.6 |
2.6±1.6 |
2.5±1.6 |
2.4±1.5 |
2.1±1.5 |
2.0±1.4 |
<0.001 |
Serum folate (ng/mL) |
14.2±15.1 |
14.5±10.5 |
14.5±23.2 |
14.2±12.4 |
14.2±8.9 |
14.1±8.0 |
13.4±8.6 |
12.2±9.3 |
0.03 |
Vitamin B6 (nmol/L) |
67.4±82.4 |
60.7±80.5 |
69.3±78.2 |
75.3±95.2 |
61.1±53.3 |
73.0±91.8 |
62.8±68.7 |
59.5±78.5 |
0.98 |
Vitamin B12 (pg/mL) |
555.2±846.6 |
511.9±429.8 |
522.4±281.7 |
569.4±688.3 |
721.4±2244.2 |
517.9±293.1 |
636.8±1605.9 |
591.7±887.5 |
0.009 |
Proportion (%) |
|
|
|
|
|
|
|
|
|
Male |
48.7 |
24.8 |
46.6 |
55.0 |
62.7 |
66.5 |
65.6 |
75.5 |
<0.001 |
Non-Hispanic white |
53.8 |
60.8 |
54.5 |
51.5 |
52.8 |
53.3 |
49.6 |
39.5 |
<0.001 |
Current smokers |
18.5 |
10.9 |
16.9 |
19.0 |
25.4 |
23.1 |
26.7 |
33.2 |
<0.001 |
Current drinkers |
71.4 |
67.0 |
67.3 |
73.8 |
79.4 |
74.8 |
73.7 |
82.2 |
<0.001 |
Physically inactive |
41.4 |
31.9 |
38.0 |
43.1 |
48.4 |
47.5 |
52.2 |
60.9 |
<0.001 |
Folate deficiency1
|
0.4 |
0.1 |
0.5 |
0.3 |
1.6 |
0.4 |
0.4 |
1.2 |
0.03 |
Vitamin B6 deficiency2
|
22.0 |
30.5 |
20.0 |
17.6 |
17.9 |
19.4 |
20.4 |
23.7 |
<0.001 |
Vitamin B12 deficiency3
|
2.2 |
2.1 |
2.2 |
2.2 |
0.8 |
1.7 |
3.7 |
3.6 |
0.17 |
Table 2.Mean homocysteine level1 (mean±standard error, μmol/L) and odds ratios1 (95% confidence intervals) for hyperhomocysteinemia depending on the categories of blood lead level among study subjects
|
Quartiles of blood lead levels
|
p-trend |
|
Q1 |
Q2 |
Q3 |
Q4
|
|
Q4-1 |
Q4-2 |
Q4-3 |
Q4-4 |
Outcome: homocysteine (μmol/L) |
|
|
|
|
|
|
|
Model 1 |
7.5±0.2 |
9.1±0.1 |
10.0±0.1 |
10.1±0.3 |
11.0±0.3 |
11.2±0.3 |
12.2±0.3 |
<0.001 |
Model 2 |
9.0±0.2 |
9.5±0.2 |
9.6±0.2 |
9.5±0.3 |
10.0±0.3 |
10.3±0.3 |
11.1±0.3 |
<0.001 |
Model 3 |
9.2±0.2 |
9.7±0.2 |
9.8±0.2 |
9.6±0.3 |
10.1±0.3 |
10.3±0.3 |
11.2±0.3 |
<0.001 |
Model 4 |
9.2±0.2 |
9.7±0.2 |
9.8±0.2 |
9.6±0.3 |
10.0±0.3 |
10.3±0.3 |
11.1±0.3 |
<0.001 |
Outcome: hyperhomocysteinemia (>15 μmol/L) |
|
|
|
|
|
|
Cases/no. |
21/971 |
49/1100 |
68/1001 |
22/252 |
20/242 |
42/270 |
50/253 |
|
Model 1 |
1.0 (reference) |
2.1 (1.3, 3.5) |
3.3 (2.0, 5.4) |
4.3 (2.3, 8.0) |
4.1 (2.2, 7.7) |
8.3 (4.8, 14.4) |
11.1 (6.6, 19.0) |
<0.001 |
Model 2 |
1.0 (reference) |
1.3 (0.7, 2.2) |
1.4 (0.8, 2.4) |
1.8 (0.9, 3.4) |
1.3 (0.7, 2.6) |
2.9 (1.6, 5.3) |
3.9 (2.2, 7.0) |
<0.001 |
Model 3 |
1.0 (reference) |
1.2 (0.7, 2.1) |
1.3 (0.8, 2.3) |
1.6 (0.8, 3.1) |
1.3 (0.6, 2.5) |
2.7 (1.5, 4.9) |
3.3 (1.8, 6.0) |
<0.001 |
Model 4 |
1.0 (reference) |
1.2 (0.7, 2.0) |
1.3 (0.8, 2.3) |
1.6 (0.8, 3.1) |
1.2 (0.6, 2.4) |
2.6 (1.4, 4.8) |
3.2 (1.7, 5.9) |
<0.001 |
Table 3.Adjusted1 homocysteine level (mean±standard error, μmol/L) and ORs (95% CIs) for hyperhomocysteinemia depending on the categories of blood lead level after stratifying by the median2 value of folate, vitamin B6, or vitamin B12
|
|
Quartiles of blood lead levels
|
|
|
Q1 |
Q2 |
Q3 |
Q4 |
p-trend |
p-interaction |
Folate |
|
|
|
|
|
|
|
<Median |
|
9.6±0.3 |
10.0±0.2 |
10.2±0.2 |
10.9±0.2 |
<0.001 |
0.06 |
≥Median |
|
9.0±0.3 |
9.3±0.2 |
9.1±0.2 |
9.3±0.2 |
0.515 |
|
Vitamin B6 |
|
|
|
|
|
|
|
<Median |
|
9.3±0.3 |
9.9±0.3 |
10.2±0.3 |
10.7±0.3 |
<0.001 |
0.002 |
≥Median |
|
9.2±0.2 |
9.5±0.2 |
9.5±0.2 |
9.8±0.2 |
0.087 |
|
Vitamin B12 |
|
|
|
|
|
|
|
<Median |
|
10.4±0.3 |
10.9±0.3 |
10.9±0.3 |
11.2±0.3 |
0.081 |
0.01 |
≥Median |
|
8.0±0.2 |
8.5±0.1 |
8.7±0.1 |
9.3±0.1 |
<0.001 |
|
ORs for hyperhomocysteinemia |
|
|
|
|
|
|
Folate |
|
|
|
|
|
|
|
<Median |
Cases/no. |
11/440 |
29/557 |
45/503 |
88/552 |
|
|
|
OR (95% CI) |
1.0 (reference) |
1.2 (0.6, 2.5) |
1.5 (0.7, 3.2) |
2.3 (1.1, 4.7) |
0.003 |
0.74 |
≥Median |
Cases/no. |
10/531 |
20/543 |
23/498 |
46/465 |
|
|
|
OR (95% CI) |
1.0 (reference) |
1.1 (0.5, 2.4) |
0.8 (0.4, 1.8) |
1.5 (0.7, 3.2) |
0.237 |
|
Vitamin B6 |
|
|
|
|
|
|
|
<Median |
Cases/no. |
7/552 |
23/505 |
43/467 |
82/520 |
|
|
|
OR (95% CI) |
1.0 (reference) |
1.9 (0.8, 4.5) |
2.7 (1.2, 6.4) |
3.8 (1.6, 9.0) |
<0.001 |
0.06 |
≥Median |
Cases/no. |
14/419 |
26/595 |
25/534 |
52/497 |
|
|
|
OR (95% CI) |
1.0 (reference) |
0.9 (0.5, 1.8) |
0.7 (0.3, 1.3) |
1.3 (0.7, 2.5) |
0.305 |
|
Vitamin B12 |
|
|
|
|
|
|
|
<Median |
Cases/no. |
15/509 |
39/541 |
50/481 |
98/513 |
|
|
|
OR (95% CI) |
1.0 (reference) |
1.3 (0.7, 2.5) |
1.3 (0.7, 2.5) |
2.0 (1.1, 3.9) |
0.012 |
0.64 |
≥Median |
Cases/no. |
6/462 |
10/559 |
18/520 |
36/504 |
|
|
|
OR (95% CI) |
1.0 (reference) |
1.0 (0.3, 2.8) |
1.4 (0.5, 3.7) |
2.7 (1.0, 7.1) |
0.005 |
|