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

Abstract

BackgroundStudies 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. ObjectiveTo assess the impact of mercury on HRV and BP among Nunavik Inuit children. MethodsA 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 2h-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. ResultsMedian cord blood mercury and blood mercury levels at 11 years old were 81.5nmoL/L (IQR: 45.0–140.0) and 14.5nmol/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 5min 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. ConclusionMercury exposure during childhood seems to affect HRV among Nunavik Inuit children at school age.