Cardiac autonomic activity and blood pressure among Inuit children exposed to mercury

doi:10.1016/j.neuro.2012.05.005

NeuroToxicology

Volume 33, Issue 5, October 2012, Pages 1067-1074

https://doi.org/10.1016/j.neuro.2012.05.005 Get rights and content

Abstract

Background

Studies conducted in the Faeroe Islands and Japan suggest a negative impact of mercury on heart rate variability (HRV) among children while the results regarding blood pressure (BP) are less consistent.

Objective

To assess the impact of mercury on HRV and BP among Nunavik Inuit children.

Methods

A cohort of 226 children was followed from birth to 11 years old. Mercury concentration in cord blood and in blood and hair at 11 years old were used as markers of prenatal and childhood exposure, respectively. HRV was measured using ambulatory 2 h-Holter monitoring while BP was measured through a standardized protocol. Simple regression was used to assess the relationship of mercury to BP and HRV parameters. Multiple linear regressions were performed adjusting for covariates such as age, sex, birth weight, body mass index (BMI), height, total n-3 fatty acids, polychlorinated biphenyls (PCB 153), lead, selenium and maternal smoking during pregnancy.

Results

Median cord blood mercury and blood mercury levels at 11 years old were 81.5 nmoL/L (IQR: 45.0–140.0) and 14.5 nmol/L (IQR: 7.5–28.0), respectively. After adjusting for the covariates, child blood mercury was associated with low frequency (LF) (β = −0.21, p = 0.05), the standard deviation of R–R intervals (SDNN) (β = −0.26, p = 0.02), the standard deviation of R–R intervals measured over 5 min periods (SDANN) (β = −0.31, p = 0.01) and the coefficient of variation of R–R intervals (CVRR) (β = −0.06, p = 0.02). No significant association was observed with BP.

Conclusion

Mercury exposure during childhood seems to affect HRV among Nunavik Inuit children at school age.

Highlights

► Mercury was associated with decreased heart rate variability during childhood. ► No association was observed between mercury during childhood and blood pressure. ► Mercury in cord blood was not associated with blood pressure. ► Mercury in cord blood was not associated with heart rate variability.

Section snippets

Background

Mercury exposure is elevated among the Inuit children and the adults from Nunavik (Northern Quebec, Canada) since this contaminant is transformed to methylmercury (MeHg) in the aquatic environment and accumulated in fish and marine mammals (Dewailly et al., 2001, Fontaine et al., 2008, Muckle et al., 2001). Data collected between 1995 and 2001 revealed average mercury concentrations in cord blood (92.5 nmol/L), maternal blood (52 nmol/L) and hair (3.7 μg/g) (Muckle et al., 2001) higher than those

Study population

This study is part of an 11-year-old follow-up assessment of a group of Inuit children from Nunavik (Arctic Québec, Canada) recruited at birth. For most of the participants, umbilical cord blood samples were obtained under the auspices of the Cord Blood Monitoring Program (CBMP) (Muckle et al., 1998). The CBMP included all newborns (n = 491) at the Tullatavik Health Center (Ungava Bay) and the Innulitsivik Health Center (Hudson Bay) between November 1993 and December 1996. Pregnant Inuit women

Results

Descriptives for mercury exposure, other contaminants, nutrients and child characteristics are presented in Table 1. Mean age was 11.3 ± 0.6 years and the sample was composed of 118 girls (52%) and 108 boys (48%). Median cord blood mercury, child blood mercury and child hair mercury concentrations were 81.5 nmol/L (IQR: 45.0–140.0), 14.5 nmol/L (IQR: 7.5–28.0) and 4.75 nmol/g (IQR: 2.5–8.3) respectively, with no significant differences between boys and girls (p > 0.05). At birth examination, boys had

Discussion

In the present study, prenatal mercury exposure was not associated with decreased HRV. However, blood mercury concentration at school age was negatively associated with HRV parameters representing the overall HRV (LF, SDNN, SDANN and CVRR) after adjustment for a set of covariates that could influence the association between mercury and the outcomes. These associations remained statistically significant after adjusting for cord blood mercury as well as fish nutrients (n-3 PUFAs and selenium),

Conclusion

The results of the present study suggest that mercury exposure during childhood decreases HRV. However, further research is needed to better understand the impact of mercury on BP in children.

Conflicts of interest statement

The authors declare that there are no conflicts of interest.

Acknowledgements

We are grateful to the Nunavik population for their participation in this study and to the medical and health care professionals from the health centers and nursing stations for their assistance. This research was funded by annual grants from Indian and Northern Affairs Canada (Northern Contaminants Program) and grants from the NIH/National Institute of Environmental Health and Sciences, Health Canada, March of Dimes Birth Defect Foundation, FRSQ-Hydro-Québec, the Joseph Young, Sr. Fund from

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Cardiac autonomic activity and blood pressure among Inuit children exposed to mercury

Abstract

Background

Objective

Methods

Results

Conclusion

Highlights

Section snippets

Background

Study population

Results

Discussion

Conclusion

Conflicts of interest statement

Acknowledgements

Sci Total Environ

Chest

Neurotoxicology

Environ Res

J Pediatr

Sci Total Environ

Chest

Sci Total Environ

J Am Coll Cardiol

Toxicol Appl Pharmacol

Am J Hypertens

Metabolism

Atherosclerosis

Ecotoxicol Environ Saf

Environ Res

Neurotoxicology

Effects of cigarette smoking on heart rate variability and plasma N-terminal pro-B-type natriuretic peptide in healthy subjects: is there the relationship between both markers?

Ann Noninvasive Electrocardiol

Assessment of pre- and postnatal exposure to polychlorinated biphenyls: lessons from the Inuit Cohort Study

Environ Health Perspect

Heart rate variability in children with idiopathic ventricular tachycardia

Clin Auton Res

Cardiovascular homeostasis in rats chronically exposed to mercuric chloride

Arch Toxicol

Interaction of mercury compounds with muscarinic receptor subtypes in the rat brain

Neurotoxicology

Effect of methylmercury on some neurotransmitters and oxidative damage of rats

J Environ Sci

Methylmercury exposure and adverse cardiovascular effects in Faroese whaling men

Environ Health Perspect

Exposure of the Inuit population of Nunavik (Arctic Quebec) to lead and mercury

Arch Environ Health

Effects of trans- and n-3 unsaturated fatty acids on cardiovascular risk markers in healthy males an 8 weeks dietary intervention study

Eur J Clin Nutr

Sympathetic tone and ventricular tachycardia

J Cardiovasc Med