Heart rate variability and peripheral nerve conduction velocity in relation to blood lead in newly hired lead workers

Abstract

ObjectivesPrevious studies relating nervous activity to blood lead (BL) levels have limited relevance, because over time environmental and occupational exposure substantially dropped. We investigated the association of heart rate variability (HRV) and median nerve conduction velocity (NCV) with BL using the baseline measurements collected in the Study for Promotion of Health in Recycling Lead (NCT02243904).MethodsIn 328 newly hired men (mean age 28.3 years; participation rate 82.7%), we derived HRV measures (power expressed in normalised units (nu) in the high-frequency (HF) and low-frequency (LF) domains, and LF/HF) prior to long-term occupational lead exposure. Five-minute ECG recordings, obtained in the supine and standing positions, were analysed by Fourier transform or autoregressive modelling, using Cardiax software. Motor NCV was measured at the median nerve by a handheld device (Brevio Nerve Conduction Monitoring System, NeuMed, West Trenton, NJ, USA). BL was determined by inductively coupled plasma mass spectrometry.ResultsMean BL was 4.54 µg/dL (IQR 2.60–8.90 µg/dL). Mean supine and standing values of LF, HF and LF/HF were 50.5 and 21.1 nu and 2.63, and 59.7 and 10.9 nu and 6.31, respectively. Orthostatic stress decreased HF and increased LF (p<0.001). NCV averaged 3.74 m/s. Analyses across thirds of the BL distribution and multivariable-adjusted regression analyses failed to demonstrate any association of HRV or NCV with BL.ConclusionsAt the exposure levels observed in our study, autonomous nervous activity and NCV were not associated with BL.Trial registration numberNCT02243904

Toxicological profile for lead

“…A small (n=179) prospective study in adults with a mean PbB of 4.18 µg/dL showed an inverse association between PbB and left ventricular systolic function, but not left ventricular diastolic function or left ventricular structure (Yang et al 2017). Results of a small (n=328) cross-sectional study in newly hired male Pb workers did not observe an association between PbB (mean 4.54 µg/dL) and heart rate variability (Yu et al 2019a). A large (n=7,179) study of NHANES III participants showed that PbB was associated 2.…”

“…≥6.25 µg/dL) (Chen et al 2017). Other studies have evaluated left ventricular function and structure, heart rate variability, and QRS-T wave angle (Jing et al 2019l Yang et al 2017Yu et al 2019a). A small (n=179) prospective study in adults with a mean PbB of 4.18 µg/dL showed an inverse association between PbB and left ventricular systolic function, but not left ventricular diastolic function or left ventricular structure (Yang et al 2017).…”

The impact of chronic co-exposure to different heavy metals on small fibers of peripheral nerves. A study of metal industry workers

“…Cadmium intoxication can lead to olfactory, neurobehavioral, and memory problems, and may underlie neurodegeneration [ 4 , 13 , 45 – 47 ]. Little is known about the influence of cadmium on the peripheral nervous system [ 15 , 48 ]. The adverse effects of cadmium on the auditory system have been described in some studies [ 18 ].…”

Impacts of Environmental Stressors on Autonomic Nervous System

“…Decreased heart rate variability implies a high heart rate. Yu et al, [32] intended to examine the association between blood lead and autonomic nervous activity (heart rate variability and median nerve conduction velocity in 328 adult males aged 28 years. The authors found no association between blood level concentration and autonomic nervous activity.…”