TABLE 2.
Study Population Characteristics for Participants at Entry (Baseline) and in Year 2 and Year 7
| Boys |
Girls |
|||||
|---|---|---|---|---|---|---|
| Entry. |
Year 2. |
Year 7. |
Entry. |
Year 2. |
Year 7. |
|
| Characteristic | mean (SD) | mean (SD) | mean (SD) | mean (SD) | mean (SD) | mean (SD) |
| Age | 10.17 (.82) | 12.22 (.84) | 17.15 (.85) | 10.14 (.93) | 12.15 (.96) | 17.06 (1.03) |
| School year | 4.05 (1.05) | 5.78 (1.21) | 9.40 (2.05) | 4.14 (1.07) | 5.91 (1.16) | 9.86 (1.51) |
| Non-Verbal IQ (at entry only) | 85.96 (9.96) | — | — | 85.54 (10.23) | — | — |
| Urinary mercury concentrations | ||||||
| Unadjusted urinary Hga | 1.45 (1.13) | 2.17 (2.14) | 1.86 (5.35) | 1.52 (1.13) | 2.83 (3.02) | 2.37 (2.61) |
| Range | (0.04, 7.70) | (0.03, 11.5) | (.01, 58.3) | (0.16, 7.09) | (0.01, 15.6) | (.01, 15.6) |
| Ln HgU (creatinine corrected)b | 0.89 (0.42) | 1.02 (0.49) | 0.62 (0.48) | 0.94 (0.48) | 1.18 (0.57) | 0.83 (0.56) |
| Range | (0.13, 2.15) | (0.04, 2.53) | (.005, 3.49) | (0.10, 3.20) | (.01, 2.81) | (.01, 2.79) |
| Calculated cumulative Hg measurec | — | — | 2.48 (0.50) | — | — | 2.74 (0.55) |
| Range | — | — | (1.32, 4.03) | — | — | (1.44, 4.13) |
| Distribution | % (n) | % (n) | % (n) | % (n) | % (n) | % (n) |
|---|---|---|---|---|---|---|
| Total subjects (n) | 163 | 159 | 120 | 167 | 152 | 119 |
| Caucasian, % (n) | 74.2% (121) | 74.2% (118) | 71.7% (86) | 71.3% (119) | 69.1% (105) | 69.7% (83) |
| COMT–rs4680 | ||||||
| Wild-type (G/G) | 33% (54) | 33% (53) | 33% (40) | 37% (61) | 37% (56) | 38% (45) |
| Heterozygous (G/A) | 50% (82) | 50% (79) | 48% (57) | 48% (80) | 49% (74) | 49% (58) |
| Homozygous mutant (A/A) | 17% (27) | 17% (27) | 19% (23) | 16% (26) | 14% (22) | 13% (16) |
| COMT–rs4633 | ||||||
| Wild-type (C/C) | 31% (51) | 31% (50) | 32% (38) | 38% (63) | 38% (58) | 39% (46) |
| Heterozygous (C/T) | 53% (87) | 53% (84) | 51% (61) | 47% (78) | 47% (72) | 48% (57) |
| Homozygous mutant (T/T) | 15% (25) | 16% (25) | 18% (21) | 16% (26) | 14% (22) | 13% (16) |
| COMT–rs4818 | ||||||
| Wild-type (C/C) | 36% (59) | 36% (57) | 39% (47) | 37% (61) | 36% (55) | 36% (43) |
| Heterozygous (C/G) | 49% (80) | 50% (79) | 48% (58) | 46% (76) | 46% (70) | 45% (54) |
| Homozygous mutant (G/G) | 15% (24) | 14% (23) | 13% (15) | 18% (30) | 18% (27) | 18% (22) |
| COMT–rs6269 | ||||||
| Wild-type (A/A) | 21% (35) | 21% (34) | 22% (26) | 24% (40) | 24% (36) | 25% (30) |
| Heterozygous (A/G) | 52% (85) | 52% (83) | 50% (60) | 52% (87) | 53% (81) | 51% (61) |
| Homozygous mutant (G/G) | 26% (43) | 26% (42) | 28% (34) | 24% (40) | 23% (35) | 24% (28) |
a
µg Hg/L.
b
ln(µg Hg/g creatinine + 1).
c
ln[Σµg Hg/g creatinine) + 1].