Table 5.

Associations between neuropsychological test scores and urinary mercury concentration [adjusted coefficient ± SE (n)].

Test score	Urinary mercury	p-Valuea
WISC-III
Factor
Verbal Comprehension	0.40 ± 0.58 (433)b	0.50
Perceptual Organization	0.65 ± 0.64 (432)	0.31
Freedom from Distractibility	−0.37 ± 0.69 (432)	0.60
Processing Speed	0.01 ± 0.80 (430)	0.99
Subtest
Verbal
Information	0.02 ± 0.16 (433)	0.89
Similarities	−0.02 ± 0.13 (433)	0.91
Vocabulary	0.17 ± 0.13 (433)	0.19
Comprehension	−0.00 ± 0.18 (433)	0.99
Digit Span	0.04 ± 0.15 (432)	0.80
Performance
Picture Completion	0.01 ± 0.18 (433)	0.94
Coding	−0.01 ± 0.19 (432)	0.97
Picture Arrangement	−0.01 ± 0.18 (432)	0.97
Block Design	0.07 ± 0.16 (433)	0.66
Object Assembly	0.29 ± 0.17 (432)	0.08
Symbol Search	0.04 ± 0.19 (430)	0.83
Mazes	−0.11 ± 0.19 (432)	0.55
WIAT
Composite
Reading	0.17 ± 0.63 (429)	0.79
Mathematics	0.57 ± 0.70 (420)	0.42
Scale
Basic Reading	0.23 ± 0.58 (432)	0.69
Reading Comprehension	0.32 ± 0.66 (429)	0.63
Numerical Operations	0.20 ± 0.78 (420)	0.79
Math Reasoning	0.58 ± 0.67 (432)	0.39
Spelling	0.38 ± 0.63 (431)	0.54
Listening Comprehension	−0.52 ± 0.62 (414)	0.40
WRAML
Index
Verbal Memory	0.31 ± 0.53 (400)	0.56
Visual Memory	0.79 ± 0.65 (402)	0.23
Learning	0.57 ± 0.68 (401)	0.40
Scale
Picture Memory	0.08 ± 0.13 (402)	0.52
Design Memory	0.01 ± 0.16 (402)	0.96
Story Memory	0.10 ± 0.15 (401)	0.52
Verbal Learning	0.11 ± 0.15 (401)	0.49
Finger Windows	0.18 ± 0.14 (402)	0.21
Sound Symbol	0.05 ± 0.15 (401)	0.74
Sentence Memory	0.04 ± 0.12 (402)	0.77
Visual Learning	0.06 ± 0.15 (401)	0.67
Number–Letter Memory	−0.03 ± 0.12 (401)	0.82
WRAVMA
Drawing	0.33 ± 0.76 (400)	0.66
Matching	−0.25 ± 0.68 (400)	0.71
Pegboard	0.23 ± 0.79 (400)	0.77
Trail-Making Test
Part A: time to complete	0.07 ± 0.30 (390)	0.83
Part A: no. of errors	−0.03 ± 0.03 (390)	0.37
Part B: time to complete	−0.26 ± 0.94 (382)	0.78
Part B: no. of errors	0.03 ± 0.05 (382)	0.51
Finger Tapping
Right hand (mean of 5 trials)	−0.42 ± 0.31 (396)	0.17
Left hand (mean of 5 trials)	−0.22 ± 0.27 (396)	0.41
Verbal Cancellation
Ordered trial: no. of errors	0.01 ± 0.19 (387)	0.98
Unordered trial: no. of errors	−0.08 ± 0.13 (387)	0.52
Verbal Fluency
Category fluency (sum of 4 trials)	−0.17 ± 0.36 (398)	0.63
Letter fluency (sum of 3 trials)	0.12 ± 0.45 (398)	0.80
Reaction Time
Mean response time (msec)	0.00 ± 0.00 (352)	0.27
Response time SD	−0.00 ± 0.01 (352)	0.91
Stroop Color–Word Interference Test
Color	−0.90 ± 0.62 (318)	0.14
Word	−0.82 ± 0.72 (317)	0.26
Color–Word	−0.04 ± 0.50 (318)	0.94
Wisconsin Card Sorting Test
No. of categories achieved	−0.07 ± 0.05 (383)	0.15
No. of trials to first category	−0.02 ± 0.26 (383)	0.93
Total errorsc	−0.63 ± 0.77 (379)	0.41
Total perseverative errorsc	−0.16 ± 0.76 (379)	0.84
Percent conceptual level responses	−0.45 ± 0.81 (379)	0.58

^aAdjusted for baseline score, randomization stratum, baseline age, sex, baseline family socioeconomic status, baseline hair mercury concentration, and baseline blood lead concentration.

^bCoefficient represents the change in test score for each unit increase in urinary mercury concentration.

^cStandard score.