Blood lead, blood pressure, and hypertension in perimenopausal and postmenopausal women

A possible association between low-level lead exposure and elevated blood pressure has been recognized for some time. Such a connection is plausible in view of findings in animal studies that lead directly affects cardiaccontractility and excitability, alters the compliance of vascular smooth muscle, and acts on central nervous system areas involved in regulating blood pressure. Lead also might influence blood pressure through the renin-angiotensin syndrome. This study examined the relation between lead exposure and blood pressure in a population-based sample of 2165 perimenopausal and postmenopausal women who participated in the Third National Health and Nutrition Examination Survey (NHANES) from 1988 to 1994. Hypertension was defined as a systolic blood pressure of 140 mm Hg or higher, a diastolic pressure of at least 90 mm Hg, or current antihypertensive medication. Blood lead levels were estimated, by spectrophotometry. The overall mean blood lead level in women 40 to 59 years of age was 2.9 μg/dL. Women with higher levels tended to be older, to smoke and drink regularly, and to be poorer and less educated than the rest of the sample. Hypertension was found in 604 women. Blood lead levels correlated with systolic, but not with diastolic, blood pressure. In addition, there was a significant dose-response relationship, with the prevalence of hypertension ranging from 19% of women in the lowest quartile of blood level to 28% in the highest quartile. Multivariate analyses showed blood lead levels to be significantly related to both systolic and diastolic blood pressure. After adjusting for age, race/ethnicity, smoking, body mass index, alcohol intake, and kidney function, a difference in blood lead levels between the lowest and highest quartiles correlated with a difference of 1.7 mm Hg systolic and 1.4 mm Hg diastolic blood pressure. The relationship between lead levels and systolic hypertension was significant in postmenopausal women but not in the premenopausal group. Diastolic hypertension as well was most closely related to blood lead quartile in postmenopausal women. These findings suggest that small increments in blood lead levels above 1 μg/dL increase blood pressure in women. This level is well below that considered to be harmful to adults. Continued efforts are needed to limit lead exposure, especially in women.