Low-Level Lead Exposure A Risk Factor For Cardiovascular Disease

by | Apr 16, 2018 | 2018, Cardiovascular Health, Environmental Health, Heavy Metals

Written by Angeline A. De Leon, Staff Writer. Study findings suggest that, of the 2-3 million U.S. deaths every year, approximately 400,000 are due to lead exposure and with blood concentrations of lead as low as 5μg/dL. associated with cardiovascular disease.

cardiovascular healthAlthough the prevalence of cardiovascular disease has significantly decreased over the last 50 years, it still remains the leading cause of death in America 1. Various studies have associated environmental lead exposure with hypertension and increased risk of cardiovascular disease, with experimental evidence suggesting that chronic exposure may trigger the development of atherosclerosis, peripheral arterial disease, and other electrocardiographic abnormalities 2-4. In one randomized controlled trial involving patients with myocardial infarction, it was demonstrated that EDTA chelation therapy (a detoxification of heavy metals from the blood stream) was associated with an 18% decrease in cardiovascular events 5. Although several population-based studies have reported that concentrations of lead in either blood or bone may be a risk factor for all-cause mortality and cardiovascular disease mortality 6, the number of deaths actually attributable to lead exposure has not been estimated in a nationally representative cohort. Moreover, studies have not yet tested the effects of low-level lead exposure (that is, lead exposure below the current action level in the U.S., 5 µg/dL) in relation to cardiovascular mortality and all-cause mortality. Scientists at Simon Fraser University in Canada (2018), therefore, sought to evaluate the relative contribution of environmental lead exposure to cardiovascular disease mortality using a population-based cohort 7.

Baseline data was gathered from a nationally representative sample of 14, 289 individuals (aged 20 years and older) enrolled in the Third National Health and Nutrition Examination Survey between 1988 and 1994. Participants completed a household interview and medical examination, during which blood and urine samples were collected. Concentrations of lead in blood and cadmium and creatinine in urine were estimated. Participants were linked to the National Death Index to identify underlying cause of death at follow-up.

At baseline, mean concentration of lead in blood was 2.71 µg/dL. During a median follow-up period of 19.3 years, 38% of recorded deaths were found to be related to cardiovascular disease and 22% to ischemic heart disease. An increase in the concentration of lead in blood from 1.0 µg/dL to 6.7 µg/dL (equivalent to the difference between the 10th to 90th percentile) was associated with significantly increased risk for all-cause mortality (Hazard Ratio = 1.37, 95% Confidence Interval: 1.17-1.60), cardiovascular disease mortality (HR = 1.70, 95% CI: 1.30-2.22), and ischemic heart disease mortality (HR = 2.08, 95% CI: 1.52-2.85). When calculating population attributable fractions, analyses indicated that if recorded concentrations of lead in blood were reduced to 1.0 µg/dL or lower, a proportional reduction of 18% was estimated for all-cause mortality (equivalent to 412,000 annual deaths), 28.7% for cardiovascular disease mortality (equivalent to 256,000 annual deaths), and 37.4% for ischemic heart disease mortality (equivalent to 185,000 annual deaths).

Comparing the relationship between concentration of lead in blood and key characteristics showed that HRs for participants younger than 50 years were significantly larger than those for participants aged 50 years or older, for all-cause mortality (HR 2·24, 95% CI 1·50–3·34 vs 1·53, 1·18–1·98; p=0·003 for interaction), cardiovascular disease mortality (2·93, 1·60–5·36 vs 2·08, 1·35–3·19; p=0·01), and ischaemic heart disease mortality (4·68, 2·42–9·05 vs 2·46, 1·51–4·01; p=0·02). The HR for cardiovascular disease mortality was significantly larger for non-smokers than smokers (HR 2·19, 95% CI 1·47–3·26 vs 1·32, 0·86–2·05; p=0·03 for interaction).

Results of the study confirm previous reports suggesting that concentrations of lead in blood or bone may be important risk factors for both all-cause mortality and cardiovascular disease mortality. Researchers conclude that the contribution of lead exposure to death rates in the U.S. is significant and that chronic environmental exposure to toxic heavy metals, even at low levels, may play a greater role than previously thought in cardiovascular disease-related death.

Source: Lanphear BP, Rach S, Auinger P, et al. Low-level lead exposure and mortality in US adult: a population-based cohort study. Lancet Public Health. 2018; 3(4): e177-e184. DOI: 10.1016/S2468-2667(18)30025-2.

© The Authors. Published by Elsevier Ltd. This is an Open Access article under the CC BY-NC-ND 4.0 license.

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Posted April 16, 2018.

Angeline A. De Leon, MA, graduated from the University of Illinois at Urbana-Champaign in 2010, completing a bachelor’s degree in psychology, with a concentration in neuroscience. She received her master’s degree from The Ohio State University in 2013, where she studied clinical neuroscience within an integrative health program. Her specialized area of research involves the complementary use of neuroimaging and neuropsychology-based methodologies to examine how lifestyle factors, such as physical activity and meditation, can influence brain plasticity and enhance overall connectivity.

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