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

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AX6-138<br />

Table AX6-5.1 (cont’d). Effects <strong>of</strong> <strong>Lead</strong> on Blood Pressure and Hypertension<br />

Reference, Study<br />

Location, and<br />

Period Study Description Pb Measurement Findings, Interpretation<br />

United States (cont’d)<br />

Proctor et al.<br />

(1996)<br />

U.S.-Boston-<br />

Normative Aging<br />

Study (VA)<br />

1992-1993<br />

798 men from 17 to 44 yrs.<br />

Multiple linear regression models<br />

<strong>of</strong> natural log blood Pb on<br />

systolic and diastolic blood<br />

pressure. All covariates <strong>for</strong>ced<br />

into model.<br />

Arithmetic mean (SD,<br />

range) blood Pb:<br />

6.5 µg/dL (4.0, 0.5-35)<br />

Natural log blood Pb, age, age-squared, BMI, adjusted dietary calcium, exercise,<br />

indicator variables <strong>for</strong> current and <strong>for</strong>mer smoker, daily alcohol consumption, sitting<br />

heart rate, and hematocrit were entered into multiple regression models without regard<br />

<strong>for</strong> significance.<br />

Increased diastolic, but not systolic, blood pressure was significantly associated with<br />

increased blood Pb. Each natural log increase in blood Pb was associated with a<br />

1.2 mm Hg (95% CI: 0.1, 2.2) increase in diastolic blood pressure.<br />

Interactions between dietary calcium and blood Pb on blood pressure were not<br />

significant. Further analyses stratified on use <strong>of</strong> antihypertensive medication and<br />

those older than or equal to 74 yrs still revealed significant blood Pb-diastolic blood<br />

pressure relationships.<br />

Blood Pb in over half the study group (n = 410) was determined by analyzing<br />

previously frozen erythrocytes collected several yrs prior to the blood pressure<br />

measurements used in the study and corrected by using hematocrit values also<br />

measured when blood was originally collected. Combining both groups means that<br />

nearly half the group was tested <strong>for</strong> the effects <strong>of</strong> blood Pb on blood pressure<br />

measured at the same time, the other half measured several yrs apart. There was no<br />

correction in models <strong>for</strong> this potential effect. The effect <strong>of</strong> taking antihypertensive<br />

medication could have been assessed in a single model by using an indicator variable.<br />

No statistical testing <strong>for</strong> the effects <strong>of</strong> stratification on the blood Pb-blood pressure<br />

relationship. No model diagnostics.

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