Claim: Higher blood lead level means slower walking pace for women

This is junk science because:

While walking speed may be a reliable measure of overall motor function in the elderly, the many potential explanations for variations in walking speed are many and are not examined adequately (or even really at all) in this study.

There is, in fact, no credible evidence in existence showing that the levels of heavy metals measured in this study are in way associated any changes in motor skills of any kind, let alone walking.

The abstract is below.

Click here for the study.

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Association between Blood Lead and Walking Speed in the National Health and Nutrition Examination Survey (NHANES 1999–2002)

Abstract

Background: Walking speed is a simple and reliable measure of motor function that is negatively associated with adverse health events in older people, including falls, disability, hospital admissions, and mortality. Lead has adverse affects on human health, particularly on the vascular and neurological systems.

Objective: We explored the hypothesis that lead is associated with slower walking speed.

Methods: We used U.S. National Health and Nutrition Examination Survey (NHANES) cross-sectional data from 1999–2002. The time to walk 20 ft (walking speed) was measured among 1,795 men and 1,798 women ≥ 50 years of age. The association between walking speed and quintiles of blood lead concentration was estimated separately in men and women using linear regression models adjusted for age, education, ethnicity, alcohol use, smoking status, height, and waist circumference.

Results: Mean blood lead concentrations and walking speeds were 2.17 μg/dL and 3.31 ft/sec in women, and 3.18 μg/dL and 3.47 ft/sec in men, respectively. Among women, walking speed decreased with increasing quintiles of blood lead, resulting in an estimated mean value that was 0.11 ft/sec slower (95% CI: –0.19, –0.04; p-trend = 0.005) for women with blood lead concentrations in the highest versus lowest quintile. In contrast, lead was not associated with walking speed in men.

Conclusion: Blood lead concentration was associated with decreased walking speed in women, but not in men. Our results contribute to the growing evidence that lead exposure, even at low levels, is detrimental to public health.

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8 responses to “Claim: Higher blood lead level means slower walking pace for women

  1. “Linear regression models”. Immediate cause for skepticism. I’ll bet there might also be an association with thinning hair<

  2. My town dates from the 5th century AD, most piping is still lead.Mine is. So far no retarded children clusters since 1845 when the first waterlines were put in, but i must admit elderly ladies tend to walk pretty slow but that’s mostly due to the fact they get really really old down here.

  3. Plumbumbphobia.

    “Lead has adverse affects on human health, particularly on the vascular and neurological systems.”

    Toxicity is in the dose. 3.18 μg/dL in adults is essentially trace. Medical concern doesn’t start till 25 μg/dL.

    I couldn’t find an explanation in the study of how lead could differentially affect men and women. Without some plausible explanation of a physiological difference between the sexes to explain the different outcomes, I say the study invalidates itself.

    “Our results contribute to the growing evidence that lead exposure, even at low levels, is detrimental to public health.”

    “Growing evidence” is scientific study speak meaning they’ve got nothing, but they’ll continue their crusade.

  4. Looks like an act of random correlation. There are a large number of physical conditions that could contribute to walking slowly. Are all of them connected to lead? My guess is the major effect is multiple birthday syndrome.

    • Ah yes, the carrots and car accidents paradox.

      90% of folks in car accidents have had carrots within 24 hours of the accident, therefore carrots cause car accidents.

  5. What gets me more than all the junk science “this is junk science because ..” is that someone – usually a government is paying for this junk with our tax money. And then there is the desire to add political spin. Governments like to control, so if you can give them some data that allows them to control, so much the better.

    Government funding is grossly biasing the sciences, producing junk science, and is largely wasted. Government should probably stick to funding research in which it has a direct interest – new munitions for a tank, for instance.

  6. DOA at the first word: “Association”.
    Correlation is not causation.

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