Blood lead levels and longitudinal language outcomes in children from 4 to 12 years.
Barbara A Lewis, Sonia Minnes, Meeyoung O Min and 5 others
PMID 29373108WHAT IT FOUND
Higher blood lead levels in early childhood were linked to poorer total, receptive and expressive language scores, and the difference was more visible later in childhood than in early childhood.
Key findings
01Blood lead samples were obtained from 278 children, and 260 completed all four language assessments.
02Each 10 μg/dL increase in blood lead level was associated with an estimated 5.25 point loss in standard total language score across ages 4, 6, 10 and 12.
03At the 5 μg/dL cutoff, the overall total language model was not significant. At the 7 μg/dL cutoff, children with higher levels had significantly poorer total, expressive and receptive language at ages 10 and 12, but not at 4 and 6.
STILL TO COME
How it was doneWhat they foundWhat it means for SLPs
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What it does not show
Blood lead level was measured only at a single childhood visit, so later changes in exposure were not captured. Blood samples were not obtained for some children, and foster parents consented less often than biological parents. The sample was urban, low-SES and predominantly African American, so results may not generalize to rural or other populations. Very high blood lead levels were not represented. Prenatal lead exposure was not measured. The original cohort was designed to study prenatal cocaine exposure, not lead exposure. Standardized language tests may carry cultural or racial bias, though scores were internally standardized.
Declared interests
The supplied text does not report funding or conflicts of interest.
The easy way to misread this
Do not read this as proof that blood lead level caused the language decline. This was an observational cohort, and blood lead level was measured at a single childhood visit, so changes in exposure and other unmeasured risks cannot be ruled out.