Reduced heart rate variability (HRV) is one of the serious risk factors for heart diseases. We evaluated the acute and chronic effects of work-related factors on HRV.

The five-minute HRV of 85 male workers from an automobile assembly factory were measured at 9 A.M. (before-work) and at 5 P.M. (after-work). The workplace noise, temperature and physical workload levels were measured as work-related factors. We postulated that the HRV measured at beforework represents the chronic effects and the HRV measured at after-work represents the acute effects of work-related factors. We used generalized linear regression analysis with adjusting for the general characteristics and/or the morning HRV.

The subjects exposed to noise or a hot environment showed increased HRV in the afternoon and decreased HRV in the morning. Machine oil and interpersonal conflict decreased the HRV in the morning, but other chemicals did not show any effect on the HRV. A physical workload decreased the HRV in both the morning and afternoon.

The physical and chemical environment, psychosocial stress and a physical workload may affect the autonomic nerve system.