| Low-Level Lead Exposure, Metabolic Syndrome, and Heart Rate Variability: The VA Normative Aging Study Sung Kyun Park,1 Joel Schwartz,1,2 Marc Weisskopf,1 David Sparrow,3 Pantel S. Vokonas,3 Robert O. Wright,1,2 Brent Coull,4 Huiling Nie,1,2 and Howard Hu1,2 1Department of Environmental Health, Harvard School of Public Health, Boston, Massachusetts, USA; 2Channing Laboratory, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts, USA; 3VA Normative Aging Study, Veterans Affairs Boston Healthcare System and the Department of Medicine, Boston University School of Medicine, Boston, Massachusetts, USA; 4Department of Biostatistics, Harvard School of Public Health, Boston, Massachusetts, USA Abstract
Background: Altered heart rate variability (HRV) , a marker of poor cardiac autonomic function, has been associated with sudden cardiac death and heart failure. Objective: We examined the association of low-level lead exposure measured in bone by K-X-ray fluorescence with alterations in HRV, and whether metabolic syndrome (MetS) or its individual components modify those associations. Methods: HRV measures [power in high-frequency (HFnorm) and low-frequency (LFnorm) in normalized units, and LF/HF] were taken among 413 elderly men from the Normative Aging Study. MetS was defined as subjects having three or more of the following criteria: abdominal obesity, hypertriglyceridemia, low high-density lipoprotein, high blood pressure, and high fasting glucose. Results: Of the subjects, 32% were identified as having MetS. Inverse but nonstatistically significant associations of both tibia and patella lead levels with HFnorm and nonstatistically significant positive relations with LFnorm and LF/HF were found in the entire cohort. There was a graded, statistically significant reduction in HFnorm and increases in LFnorm and LF/HF in association with an increase in patella lead as the number of metabolic abnormalities increased. We also observed that higher patella lead was consistently associated with lower HFnorm and higher LFnorm and LF/HF among subjects with MetS or its individual components. No statistically significant interaction between MetS and tibia lead was observed. Conclusion: The results suggest that elderly men with MetS were more susceptible to autonomic dysfunction in association with chronic lead exposure as measured in patella. The modification by MetS is consistent with a role for oxidative stress in lead toxicity on the cardiovascular system. Key words: autonomic nervous system, bone lead, heart rate variability, hypertension, metabolic syndrome. Environ Health Perspect 114:1718–1724 (2006) . doi:10.1289/ehp.8992 available via http://dx.doi.org/ [Online 3 August 2006]
Address correspondence to S.K. Park, SPH II-M6240, Department of Environmental Health Sciences, University of Michigan School of Public Health, 109 S. Observatory St., Ann Arbor, MI 48109. Telephone: (734) 936-1719. Fax: (734) 763-8095. E-mail: sungkyun@umich.edu We thank E.R. Dibbs and J.D. Awerbach for their invaluable assistance in conducting the heart rate variability measurements and other contributions to the VA Normative Aging Study. We also thank H. Guan for obtaining bone lead data. This work was supported by National Institute of Environment Health Sciences (NIEHS) grants ES00002, ES05257, P42-ES05947, and ES10798, and U.S. Environmental Protection Agency grant EPAR827353. The VA Normative Aging Study is supported by the Cooperative Studies Program/Epidemiology Research and Information Center of the U.S. Department of Veterans Affairs and is a component of the Massachusetts Veterans Epidemiology Research and Information Center (Boston, MA) . S.K.P. was supported by Training Grant T32 ES07069 from the NIEHS. The contents of this article are solely the responsibility of the authors and do not necessarily represent the official views of the NIEHS. The authors declare they have no competing financial interests.
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