Air Quality Criteria for Lead Volume II of II - (NEPIS)(EPA) - US ...

AX6-141
Table AX6-5.1 (cont’d). Effects of Lead on Blood Pressure and Hypertension
Reference, Study
Location, and
Period Study Description Pb Measurement Findings, Interpretation
United States (cont’d)
Schwartz (1995)
15 prior U.S. and
European studies
published between
1985 and 1993
Schwartz (1991)
NHANES II
U.S.
1976-1980
Total subjects not specified, men and
women ages 18 to 74 yrs. Random
effects meta-analysis with inverse
variance weighting of Pb-blood
pressure coefficients from each study.
Sensitivity analysis performed by
dropping study with largest or smallest
effect.
Under 10,000 subjects (exact number
not reported), males and females, aged
25 to 74 yrs for left ventricular
hypertrophy results with logistic
regression. Linear blood Pb used for
LVH. For blood pressure results,
multiple linear regressions stratified by
sex, with one block of variables
forced, another block of variables
entered with stepwise regression, aged
6 mos to 74 yrs, exact number not
given. Natural log blood Pb used for
linear regression. Both logistic and
linear regressions adjusted for survey
design.
Blood Pb levels not
stated.
No blood Pb
descriptive data
given.
Each doubling of natural log blood Pb level was associated with an increase of 1.25
mm Hg (95% CI: 0.87, 1.63) systolic blood pressure. Sensitivity analysis showed
negligible change in meta-analysis coefficient. Concluded that adding newer studies
would not change calculated coefficient. Noted Pb-blood pressure slope was larger at
lower Pb levels than at higher Pb levels.
The study only analyzed systolic, not diastolic, blood pressure. Superseded by
Nawrot et al. (2002).
Used logistic regression to study Pb effect on left ventricular hypertrophy (LVH)
determined by a combination of electrocardiogram parameters and body habitus,
controlling for age, race, and sex. Every 10 µg/dL blood Pb increase was associated
with increased odds of LVH of 1.33 (95% CI: 1.20, 1.47). Interaction terms for race
by blood Pb and sex by blood Pb were not significant.
Blood pressure models stratified by sex always included BMI, age and age-squared,
race, and natural log blood Pb. Male blood pressure model also included family
history of hypertension, cholesterol, height, cigarette use, serum zinc, and tricep skin
fold. Female model also included serum zinc, family history of hypertension, tricep
skin fold, and cholesterol. Every 1 natural log unit of blood Pb increase was
associated with an increase in diastolic blood pressure of 2.93 mm Hg (95% CI: 0.93,
4.98) in males and 1.64 mm Hg (95% CI: 0.27, 3.01). Used interaction terms for
race-blood Pb and sex-blood Pb in a non-stratified model and found no significant
effect of race or sex on the blood Pb-blood pressure coefficient.
Incomplete reporting of subject size for models and for descriptive statistics for all
variables in models. Tested both linear and log transformed Pb in preliminary testing.
Found log Pb had lower probability values than linear Pb for blood pressure, and
linear Pb had lower probability values than log Pb for LVH. No testing of significant
difference between the two blood Pb specifications. No model diagnostics reported.
Only reported diastolic blood pressure results.