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

AX6-137
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)
Nash et al. (2003)
U.S.-NHANES III
1988-1994
1084 premenopausal and 633
postmenopausal women, from 40
to 59 yrs. Multiple linear
regression models with
covariates, including linear blood
Pb, entered as a block for systolic
and diastolic blood pressure.
Logistic regression models with
same covariates and Pb quartile
added last for hypertension.
Mean (range) blood Pb by
Pb quartile:
1st quartile 1.0 µg/dL
(0.5-1.6)
2nd quartile 2.1 µg/dL
(1.7-2.5)
3rd quartile 3.2 µg/dL
(2.6-3.9)
4th quartile 6.4 µg/dL
(4.0-31.1)
Linear blood Pb was entered last after forcing in age, race/ethnicity, alcohol use,
cigarette smoking, BMI, and kidney function (serum creatinine) in multiple regression
models for all women and women stratified by menopause status for systolic and
diastolic blood pressure. Pb quartile was added to logistic regression models of
hypertension (systolic ∃140 mm Hg, diastolic ∃90 mm Hg or taking antihypertensive
medication with the same covariates as the blood pressure models, in all women and
stratified by menopausal status. Tested additional models in which women treated for
hypertension were excluded from models. All models were adjusted for sample
design and weighting.
Each increase of 1 µg/dL of blood Pb was significantly associated with a 0.32 mm Hg
(95% CI: 0.01, 0.63) increase of systolic blood pressure and a 0.25 mm Hg (95% CI:
0.07, 0.43) increase of diastolic blood pressure in all women without respect to
menopausal status. In analyses stratified by menopausal status, only postmenopausal
women showed a significant blood Pb effect. For each 1 µg/dL increase of blood Pb
was associated with significantly increased diastolic blood pressure of 0.14 (95% CI:
−0.11, 0.39 sic.) only in postmenopausal women.
Referenced to the 1st blood Pb quartile, no other quartile showed significantly
increased odds for hypertension in all subjects or in subjects stratified by menopausal
status. With further analyses stratified by systolic and diastolic hypertension without
women taking antihypertensive medications, in the combined group of pre and
postmenopausal women the odds of diastolic hypertension were significant when the
4th Pb quartile was compared to the 1st quartile (OR = 3.4 [95% CI: 1.3, 8.7]). In a
model of only postmenopausal women untreated for hypertension, odds of diastolic
hypertension were significantly increased in the higher three quartiles of blood Pb
(OR = 4.6 [95% CI: 1.1, 19.2], OR = 5.9 [95% CI: 1.5, 23.1], OR = 8.1 [95% CI:
2.6, 24.7], respectively) and odds of systolic hypertension were significant only for the
two middle Pb quartiles (OR = 3.0 [95% CI: 1.3, 6.9], OR = 2.7 [95% CI: 1.2, 6.2],
respectively).
Linear blood Pb is suspect in linear regression models of blood pressure as it is
usually associated with biased and inefficient estimation of Pb coefficients due to
probable heteroscedasticity and non-normal distribution of residuals. No model
diagnostics were reported. No statistical testing for differences in Pb coefficients
according to strata. Nine stratified models overall. Not all stated significance levels
and standard errors in the blood pressure model table corresponded for certain
variables.