Association of blood lead concentrations with mortality in older women: a prospective cohort study

Abstract

Background: Blood lead concentrations have been associated with increased risk of cardiovascular, cancer, and all-cause mortality in adults in general population and occupational cohorts. We aimed to determine the association between blood lead, all cause and cause specific mortality in elderly, community residing women.

Methods: Prospective cohort study of 533 women aged 65-87 years enrolled in the Study of Osteoporotic Fractures at 2 US research centers (Baltimore, MD; Monongahela Valley, PA) from 1986-1988. Blood lead concentrations were determined by atomic absorption spectrometry. Using blood lead concentration categorized as < 8 microg/dL (0.384 micromol/L), and > or = 8 microg/dL (0.384 micromol/L), we determined the relative risk of mortality from all cause, and cause-specific mortality, through Cox proportional hazards regression analysis.

Results: Mean blood lead concentration was 5.3 +/- 2.3 microg/dL (range 1-21) [0.25 +/- 0.11 micromol/L (range 0.05-1.008)]. After 12.0 +/- 3 years of > 95% complete follow-up, 123 (23%) women who died had slightly higher mean (+/- SD) blood lead 5.56 (+/- 3) microg/dL [0.27(+/- 0.14) micromol/L] than survivors: 5.17(+/- 2.0) [0.25(+/- 0.1) micromol/L] (p = 0.09). Women with blood lead concentrations > or = 8 microg/dL (0.384 micromol/L), had 59% increased risk of multivariate adjusted all cause mortality (Hazard Ratio [HR], 1.59; 95% confidence interval [CI], 1.02-2.49) (p = 0.041) especially coronary heart disease (CHD) mortality (HR = 3.08 [CI], (1.23-7.70)(p = 0.016), compared to women with blood lead concentrations < 8 microg/dL(< 0.384 mumol/L). There was no association of blood lead with stroke, cancer, or non cardiovascular deaths.

Conclusion: Women with blood lead concentrations of > or = 8 microg/dL (0.384 micromol/L), experienced increased mortality, in particular from CHD as compared to those with lower blood lead concentrations.

Figure 1

Cumulative survival with blood lead concentrations < 8 μg/dL (< 0.384 μmol/L), and ≥ 8 μg/dL (≥ 0.384 μmol/L) in women in SOF. Cumulative survival associated with blood lead concentrations < 8 μg/dL (< 0.384 μmol/L), and ≥ 8 μg/dL (≥ 0.384 μmol/L), in women in SOF lead ancillary study (Log rank test P < 0.007)

Figure 2

Adjusted hazards ratios and 95% confidence interval of mortality in SOF participants with blood lead concentrations ≥ 8 μg/dL (≥ 0.384 μmol/L). Adjusted hazard ratios and 95% confidence interval of all cause mortality and cause specific mortality in SOF lead ancillary study participants with blood lead concentrations ≥ 8 μg/dL (≥ 0.384 μmol/L), compared to referent < 8 μg/dL (< 0.384 μmol/L),