CUMULATIVE LEAD EXPOSURE AND CHANGE IN COGNITION AMONG ELDERLY MEN: THE VA NORMATIVE AGING STUDY

Abstract

ISEE-361 Introduction: Lead exposure has been found to affect cognitive function in several different populations. Although several cross sectional studies of adults suggest that lead exposure affects cognitive function, only one study, among former organolead workers, was longitudinal, looking at the effect on cognitive function over time. Whether chronic low-level environmental (non-occupational) exposure to lead results in cognitive decline among adults has not been examined. Methods: We assessed the relation between biomarkers of lead exposure (including bone lead measured with K-X-ray fluorescence) and change in Mini-Mental State Examination (MMSE) scores in the VA Normative Aging Study, a cohort of elderly men from the New England area in the United States who are interviewed every 3-5 years. We obtained parameter estimates for the effect of increasing lead biomarkers on change in MMSE score using generalized additive models controlling for potential confounders. Results: There were 466 subjects who took the MMSE at least twice between 1993 and 2001 and had bone lead concentrations measured with K-X-ray fluorescence between 1991 and 1997. The men were 67.4 (sd=6.6) years old at the first MMSE test, and the mean time between the two tests was 3.5 years (sd=1.1). The change in MMSE score over this period associated with an interquartile range increase in patella bone lead concentration (20 microg/g bone mineral) was -0.23 (95% CI: -0.38, -0.08), after adjustment for age, education, smoking, alcohol intake, and time between MMSE tests. This effect is approximately that of 6 extra years of age on baseline MMSE score in our data. For tibia lead the association with an interquartile range increase (14 microg/g bone mineral) was weaker (-0.13; 95% CI: -0.29, 0.04), and for blood lead (interquartile range: 2 microg/dL) there was no association (-0.02; 95% CI: -0.11, 0.08). Conclusions: Higher patella bone lead levels are associated with a steeper decline over time in performance on the MMSE test among non-occupationally exposed elderly men.