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

AX6-133
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)
Glenn et al. (2003)
U.S.-New Jersey
1994-1998
496 males, mean (SD, range) age
55.8 (7.4, 40-71) yrs, working or
formerly working at a plant
producing tetraethyl or tetramethyl
Pb until 1991, were followed from
10 mos to 3.5 yrs during which
blood pressure was repeatedly
tested. Blood Pb was tested only at
baseline. Tibia Pb was tested in
1991 (at the end of organic Pb
production at the plant) and called
“peak tibia Pb” and again during
1997 (yr 3). Generalized estimating
equations with an exchangeable
correlation structure for repeated
measurements were used for systolic
and diastolic blood pressure. One
group of covariates was forced into
the model as a block (age at
baseline, race, BMI, indicator
variable for technician, Pb variable
(linear blood Pb, peak tibia Pb, and
tibia Pb each tested separately),
duration of follow up, and the
interaction between the Pb variable
and the duration term. Potential
confounding variables were entered
stepwise and retained in the model if
significant. Alternate models not
using linear time were constructed,
using quartile of follow up time to
avoid assuming a linear relationship
of change in blood pressure with
time.
Arithmetic mean (SD, range)
blood Pb at baseline:
4.6 µg/dL (2.6, !1 to 20)
Tibia Pb at yr 3:
14.7 µg/g (9.4, !1.6 to 52)
Peak tibia Pb:
24.3 µg/g (18.1, !2.2 to
118.8)
Controlling for baseline age, BMI, antihypertensive medication use, smoking,
education, technician and number of yrs to each blood pressure measurement,
each 1 µg/dL increase in linear baseline blood Pb was associated with avg
systolic blood pressure increase of 0.64 mm Hg/yr (95% CI: 0.14, 1.14),
each 10 µg/g increase in yr 3 tibia Pb with an avg increase of 0.73 mm Hg/yr
(95% CI: 0.23, 1.23), and each increase of 10 µg/g of peak tibia Pb with an
avg increase of 0.61 mm Hg/yr (95% CI: 0.09, 1.13). Similar results were
obtained using the follow up time quartile designation for systolic blood
pressure with all subjects and with subjects not taking antihypertensive
medications.
This was one of the few studies using a prospective design and that used a
statistical technique accounting for repeated measures. No justification given
for using an exchangeable correlation structure instead of an alternate one.
Only examined cortical bone Pb (tibia) and not trabecular bone Pb (patella or
calcaneus). Linear blood Pb may not be indicated for use in blood Pb-blood
pressure models. Stepwise modeling involves multiple testing of the same
data set with no control for altered probabilities. No model diagnostics
presented.