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. Author manuscript; available in PMC: 2017 Jun 14.
Published in final edited form as: Am J Ind Med. 2008 May;51(5):336–343. doi: 10.1002/ajim.20573

TABLE IV.

Linear regression modelsa of effect modification by VDR and ALAD genotypes on associations between lead dose and systolic blood pressure among 652 Korean lead workers

Independent variable β coefficient SE β p-value Model r2
Model 1
 ALAD12 −0.2437 1.9578 0.90 0.18
 Patella lead, μg/g 0.0063 0.0085 0.46
 Patella* ALAD12 −0.0127 0.0304 0.68
Model 2
 VDR Bb or BB −0.1503 1.7816 0.93 0.18
 Patella lead, μg/g 0.0030 0.0083 0.72
 Patella* VDR Bb or BB −0.0041 0.0160 0.80
Model 3
 ALAD12 −0. 2323 1.9355 0.90 0.19
 Blood lead, μg/dL 0.1030 0.0415 0.01
 Blood* ALAD12 −0.0447 0.1176 0.70
Model 4
 VDR Bb or BB −0.7937 1.8222 0.66 0.19
 Blood lead, μg/dL 0.0972 0.0426 0.02
 Blood* VDR Bb or BB −0.0068 0.0935 0.94
a

The models also controlled for age (linear and quadratic terms), gender, body mass index, lead job duration, antihypertensive medication use, and cumulative lifetime drinks in current alcohol users (divided into quartiles).

b

The common gene allele is the reference group (italized); the beta coefficient for this term is therefore the slope for the association between the lead variable and systolic blood pressure in workers with the common genotype. The slope in workers with the variant allele is obtained by adding the beta coefficient of the cross-product term (below the reference category) to the beta coefficient of the reference category (i.e., the slope for the association between patella lead and systolic blood pressure in workers with the variant ALAD2 allele is −0.0064 [0.0063 + −0.0127]). P-values for the cross-product terms of gene and lead dose reflect the statistical significance of the difference between the slopes of the regression lines in participants with the variant gene and those with the common gene.