Environmental lead exposure and cognitive function in community-dwelling older adults.
OBJECTIVE
To determine if long-term exposure to high levels of lead in the environment is associated with decrements in cognitive ability in older Americans.


METHODS
We completed a cross-sectional analysis using multiple linear regression to evaluate associations of recent (in blood) and cumulative (in tibia) lead dose with cognitive function in 991 sociodemographically diverse, community-dwelling adults, aged 50 to 70 years, randomly selected from 65 contiguous neighborhoods in Baltimore, MD. Tibia lead was measured with (109)Cd induced K-shell X-ray fluorescence. Seven summary measures of cognitive function were created based on standard tests in these domains: language, processing speed, eye-hand coordination, executive functioning, verbal memory and learning, visual memory, and visuoconstruction.


RESULTS
The mean (SD) blood lead level was 3.5 (2.2) microg/dL and tibia lead level was 18.7 (11.2) microg/g. Higher tibia lead levels were consistently associated with worse cognitive function in all seven domains after adjusting for age, sex, APOE-epsilon4, and testing technician (six domains p <or= 0.01, one domain p <or= 0.05). Blood lead was not associated with any cognitive domain. Associations with tibia lead were attenuated after adjustment for years of education, wealth, and race/ethnicity.


CONCLUSIONS
Independent of recent lead dose, retained cumulative dose resulting from previous environmental exposures may have persistent effects on cognitive function. A portion of age-related decrements in cognitive function in this population may be associated with earlier lead exposure.
Shih
R A
RA
Department of Mental Health, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD 21205, USA.
Glass
T A
TA
Bandeen-Roche
K
K
Carlson
M C
MC
Bolla
K I
KI
Todd
A C
AC
Schwartz
B S
BS
D000367:Age Factors; D000368:Aged; D053327:Apolipoprotein E4 / Q000235:genetics; D001774:Blood Chemical Analysis / Q000592:standards; D001842:Bone and Bones / Q000737:chemistry* / Q000187:drug effects / Q000378:metabolism; D003072:Cognition Disorders / Q000139:chemically induced / Q000175:diagnosis* / Q000523:psychology; D015331:Cohort Studies; D003430:Cross-Sectional Studies; D004522:Educational Status; D004781:Environmental Exposure / Q000009:adverse effects*; D005260:Female; D006801:Humans; D007854:Lead / Q000032:analysis* / Q000097:blood / Q000633:toxicity; D020263:Lead Poisoning, Nervous System / Q000175:diagnosis* / Q000453:epidemiology / Q000378:metabolism; D008297:Male; D008403:Mass Screening / Q000379:methods / Q000592:standards; D008875:Middle Aged; D009483:Neuropsychological Tests; D015588:Observer Variation; D011237:Predictive Value of Tests; D012737:Sex Factors; D012959:Socioeconomic Factors; D013052:Spectrometry, X-Ray Emission / Q000592:standards; D013977:Tibia / Q000737:chemistry / Q000187:drug effects / Q000378:metabolism
D053327:Apolipoprotein E4; D007854:Lead