Something in the Air? Ambient Lead Linked to Alzheimers Deborah Brauser March 18, 2014 ORLANDO, Florida ― Even exposure to very low levels of ambient lead appears to increase the risk for conversion from amnestic mild cognitive impairment (aMCI) to Alzheimers disease (AD), new research suggests. Using data from the Alzheimers Disease Neuroimaging Initiative (ADNI), investigators found that patients with aMCI who converted to AD had significantly greater ambient lead exposure than did nonconverters. Further analysis showed that lead exposure also significantly predicted atrophy of the hippocampus, as well as entorhinal cortex atrophy and thickness reduction. We know about studies showing adverse effects from lead in children. So I wasnt that surprised by our findings, lead author Linda Mah, MD, assistant professor in the Division of Geriatric Psychiatry at the University of Toronto, Ontario, Canada, and a clinician scientist at the Rotman Research Institute at Baycrest, a hospital in Toronto, told Medscape Medical News. However, I was surprised that the average amount of ambient lead exposure did predict size of hippocampal volume at follow-up. Those findings were not robust, but they were significant, added Dr. Mah. The results were presented here at the American Association for Geriatric Psychiatry (AAGP) 2014 Annual Meeting. Neurotoxic Lead is a confirmed neurotoxicant that is associated with neurodevelopmental deficits in children following even very low lead exposure, write the investigators. Air quality has recently been linked to risk of AD, but whether ambient lead exposure increases risk of AD is unknown, they add. The researchers examined data from ADNI, which was originally created as a multisite study of 265 older patients with aMCI between the ages of 55 and 90 years. Criteria for aMCI included subjective and objective memory loss during activities of daily living. For the current analysis, the investigators were able to match air quality measures and lead levels to only 61 of the participants (63% men; mean age, 76 years), using city reports from the US Environmental Protection Agency (EPA). Although ADNI includes patients from all of North America, Canada does not track lead levels as a measure of air quality. As a result, all 61 participants for the current study lived in US cities. In addition to assessing conversion from aMCI to AD in these patients, neuroimaging was used to measure hippocampal and entorhinal cortical volume and entorhinal cortical thickness during a 3- to 5-year follow-up period. Need to Track Lead Levels Results showed that 23 patients (60% men) converted from aMCI to AD during the study period. And these patients had significantly greater ambient lead exposure, as determined on the basis of EPA measures, than patients who did not convert (P = .045). Atrophy of the hippocampus (P = .04) and of the entorhinal cortex (P = .03) and reduction in entorhinal cortical thickness (P = .02) were all significantly predicted by ambient lead exposure. The lead levels for all participants did not exceed the safety threshold set by the EPA, which is currently 0.15 μg/m3. These findings suggest ambient lead exposure is associated with greater risk of AD and AD-related neuroimaging abnormalities in aMCI, and extend the growing body of literature suggesting neurotoxic effects may occur even with very low levels of lead exposure, write the investigators. At a minimum, these findings support the need to include [this] exposure as a standard measure of air quality in order to further investigate its potential link to AD, and the need to re- evaluate the maximum threshold of lead exposure considered safe for humans. The researchers add that lowering the current EPA standard should be considered. I thought it was interesting that size of the particle air did not predict conversion, and neither did other things, such as sulphur or carbon monoxide. But with lead, there seemed to be this relationship, said Dr. Mah. And Im concerned. Air quality is not really something you can get away from. So I would really like to see, at least in Canada, for cities to start tracking their lead levels, she added. Worthy of Further Research Iqbal Ike Ahmed, MD, clinical professor of psychiatry and geriatric medicine at the University of Hawaii at Manoa, told Medscape Medical News that although the study used 2 different datasets, which means you can question some of what they found, the results were worthy of further research Its an interesting stimulus to make us look more at the neurotoxic effects of lead. And it replicates some things that have already been reported, said Dr. Ahmed, who is also a member of the board of directors for the AAGP. I did think it was fascinating that with the association with the hippocampal atrophy and the entorhinal atrophy, we can expect a conversion to Alzheimers. Dr. Ahmed, who was not involved with this research, noted that larger, prospective studies conducted in a systematic fashion are now needed to look into this association. Still, he added that it might be worthwhile for clinicians to check to see whether a patient is from an area known for high levels of lead or other toxins or other risk factors. This may be an association thats reflective of something else, or a marker, rather than a causal thing. On the other hand, the correlation with the higher lead levels is thought provoking, said Dr. Ahmed. Overall, its an interesting approach, but this is really a hypothesis-generating study rather than a hypothesis-confirmatory one. The study authors and Dr. Ahmed report no relevant financial relationships. American Association for Geriatric Psychiatry (AAGP) 2014 Annual Meeting. Abstract NR-13. Presented March 15, 2014. Medscape Medical News © 2014 WebMD, LLC
Posted on: Tue, 18 Mar 2014 16:43:35 +0000
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