Studies of blood lead levels in men suggest that elevated levels increase the risk for hypertension, perhaps through direct effects on the heart, vascular muscle, or central nervous system, or through nephrotoxicity. Blood lead levels appear to increase in women during menopause because of mobilization of skeletal stores from bone. However, this effect has not been thoroughly studied. Nash and colleagues conducted a population-based study to examine the relationship of blood lead levels with hypertension in women.
The study population included perimenopausal and postmenopausal women from the Third National Health and Nutrition Study. Participants were evaluated for blood pressure, blood lead levels, menopause status, and kidney function as indicated by the serum creatinine level. Multiple linear regression models were used to examine the association of blood lead levels with systolic and diastolic blood pressures.
The mean blood lead level for the study population was 2.9 mcg per dL (0.15 mmol per L; range, 1.0 to 6.3 mcg per dL [0.05 to 0.30 mmol per L]). Of the 2,165 women studied, 604 were hypertensive (373 treated and 231 untreated), with a systolic blood pressure of at least 140 mm Hg and a diastolic blood pressure of at least 90 mm Hg. Blood lead quartile was significantly associated with systolic but not diastolic blood pressure. A significant dose response existed between blood lead quartile and general hypertension prevalence, with 19.4 percent of hypertensive women in the lowest lead quartile compared with 28.3 percent in the highest quartile. This association was not specifically related to systolic or diastolic blood pressure.
In multivariate analyses, blood lead levels were significantly associated with systolic and diastolic blood pressure, with a difference of 1.7 mm Hg between the lowest and highest quartiles. The adjusted odds ratios (ORs) for general hypertension were elevated but not significantly (1.3 for quartile 3 and 1.4 for quartile 4). A weak association was found between blood lead levels and untreated systolic hypertension; women in the fourth quartile had the highest OR (1.55). A clear dose response was found for diastolic blood pressure, with ORs of 1.5 for women in the second quartile, 2.1 in the third quartile, and 3.4 in the fourth quartile. Postmenopausal women had significantly elevated ORs of systolic pressures in the second and third quartiles compared with women in the lowest quartile, and a dose-response association was found in diastolic blood pressure in postmenopausal women.
The authors conclude that a significant association was found between blood lead levels and increased systolic and diastolic blood pressures in U.S. women between 40 and 59 years of age, with a risk increase of 3.4-fold for diastolic hypertension in the highest blood lead quartiles compared with the lowest. Elevated blood lead levels were a predictor of increased systolic and diastolic blood pressure. The associations between blood lead levels and blood pressure were much stronger in postmenopausal women than in premenopausal women. The authors emphasize the importance of these findings; the low lead levels of the study population indicate the influence of even small increments in blood lead level.