Skip to main content
. Author manuscript; available in PMC: 2012 Dec 17.
Published in final edited form as: Epidemiology. 2009 Nov;20(6):831–839. doi: 10.1097/EDE.0b013e3181b5f100

Table 2.

Tests of changing effect hypotheses from fully-adjusted models, Baltimore Memory Study, 2001-2005. The p-value evaluates whether there is evidence of a progressive or reversible effect.

Domain Low-lead linear1 Beta (95% CI) High-lead linear spline1 Beta (95% CI) Test statistic2 (2 df) P-value
All study subjects, N = 9643
Language -0.015 (-0.050, 0.020) 0.014 (-0.028, 0.056) 1.0 0.60
Processing speed -0.011 (-0.084, 0.061) 0.008 (-0.084, 0.100) 0.26 0.88
Eye-hand coordination -0.036 (-0.075, 0.004) 0.020 (-0.027, 0.068) 11 0.0035
Executive functioning -0.001 (-0.041, 0.039) -0.008 (-0.062, 0.047) 0.59 0.74
Verbal memory & learning 0.033 (-0.017, 0.083) -0.053 (-0.116, 0.009) 3.2 0.20
Visual memory 0.017 (-0.038, 0.071) -0.022 (-0.091, 0.048) 0.38 0.83
African-Americans subjects only, N = 394
Language -0.010 (-0.082, 0.062) 0.006 (-0.078, 0.091) 0.46 0.79
Processing speed -0.020 (-0.175, 0.134) 0.023 (-0.161, 0.207) 0.07 0.97
Eye-hand coordination -0.055 (-0.142, 0.033) 0.028 (-0.069, 0.125) 10 0.0062
Executive functioning 0.065 (-0.025, 0.154) -0.091 (-0.203, 0.021) 2.7 0.27
Verbal memory & learning -0.010 (-0.097, 0.077) 0.003 (-0.109, 0.115) 0.41 0.82
Visual memory 0.013 (-0.094, 0.120) -0.011 (-0.138, 0.116) 0.11 0.94
White subjects only, N = 517
Language -0.025 (-0.068, 0.017) 0.022 (-0.033, 0.076) 2.2 0.34
Processing speed -0.015 (-0.097, 0.067) 0.011 (-0.101, 0.123) 0.33 0.85
Eye-hand coordination -0.030 (-0.075, 0.014) 0.029 (-0.028, 0.086) 2.3 0.32
Executive functioning -0.041 (-0.083, 0.002) 0.052 (-0.003, 0.107) 3.5 0.17
Verbal memory & learning 0.056 (-0.004, 0.116) -0.086 (-0.166, -0.007) 5.9 0.051
Visual memory 0.034 (-0.038, 0.106) -0.053 (-0.145, 0.039) 1.4 0.49
1

Low-lead linear term estimates the yearly change in the adjusted lead relation over lead values between 0 and 15 μg/g; high-lead linear spline term estimates the difference between the yearly change in the adjusted lead relation over lead values greater, and less than, 15 μg/g. Lead relation is given as units of domain score per 12.7 μg/g (IQR) of tibia lead.

2

Bivariate Wald test for the null hypothesis that both lead coefficients equal 0, with chi-square reference distribution

3

The stratified total does not add up to this grand total because 53 subjects of mixed race/ethnicity or other race/ethnicity were not included in the two strata.