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Low Blood Lead Levels Associated With Hypertension In Middle-Aged Women

There is a significant association between low levels of blood lead and both systolic and diastolic hypertension among 40-to-59-year-old women, according to data from the Third United States National Health and Nutritional Examination Survey (NHANES III).

Levels for the association are surprisingly low, say investigators led by Dr. Denis Nash of the University of Maryland in Baltimore and the New York City Department of Health and Mental Hygiene. "From a public health prospective, the most important and troubling implication of these findings is that lead appears to increase blood pressure in women at very small increments above 1.0 (mu)g/dL, well below what is considered deleterious in adults."

"These results demonstrate effects of lead at levels less than the US occupational blood lead exposure limits (40 [mu] g/dL) and even less than the current Centres for Disease Control and Prevention level of concern for preventing lead poisoning in children (10 [mu]g/dL)," they point out.

The researchers say that the relationship between blood lead and hypertension is most pronounced in post-menopausal women. They suggest the results support the need for further studies on the health effects of bone lead mobilisation during the menopausal transition as well as for continued efforts to reduce lead levels, especially among women.

The cross-sectional cohort used included 2,165 women participating in household interviews and physical examinations for NHANES III from 1988 to 1994. Covariates considered were age, race/ethnicity, smoking status, body mass index, alcohol use and kidney function.

Change in blood lead levels from the lowest to highest quartiles was associated with small, statistically significant adjusted changes in systolic and diastolic blood pressures. Women in the highest quartile were at increased risk of diastolic hypertension (adjusted odds ratio [OR], 3.4). They were also at moderately increased risk of general hypertension (adjusted OR, 1.4) and systolic hypertension (adjusted OR, 1.5).

In post-menopausal women, the adjusted OR for diastolic hypertension increased with the increasing quartile of blood lead level. Compared with quartile 1, the adjusted OR for quartile 2 was 4.6. It was 5.9 for quartile 3 and 8.1 for quartile 4.

The researchers say a difference in blood lead levels between the lowest and highest quartiles was associated with a difference of 1.7 mm Hg in systolic blood pressure and 1.4 mm Hg in diastolic blood pressure. They add that blood lead is also among the few predictors of both systolic and diastolic blood pressures in peri- menopausal women.
JAMA, 2003;289:12:1523-1532.

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