Assessment of autonomic neurotoxicity in occupational and environmental health as determined by ECG R‐R interval variability: A review

Measurement of heart rate variability (coefficient of variation of ECG R-R intervals, CVRR) provides a useful approach for the objective assessment of the autonomic nervous function. It is noninvasive and clinically practical, although it tends to be distorted by confounding factors such as age, alcohol, and tobacco. Specifically, two component coefficients of variation of the respiratory sinus arrhythmia (RSA) and Mayer wave-related sinus arrhythmia (MWSA) in the CVRR (i.e., C-CVRSA and C-CVMWSA), computed from component spectral powers by autoregressive spectral and component analyses, are expected to reflect parasympathetic and sympathetic functions, respectively. This article is intended to present an overview of research, utilizing the CVRR method including the C-CVRSA and C-CVMWSA, in occupational and environmental health. The available literature, addressing the impact of some chemicals and work-related factors on human autonomic nervous system, indicates that parasympathetic activity appears to be more vulnerable to these factors than does sympathetic activity. Since decreased cardiac vagal tone is associated with an increased risk of sudden cardiac death or coronary artery disease, attention should be directed to further discovery of hazardous factors in the environment and work place, which are likely to affect the autonomic nervous system.