Effects of high occupational physical activity, aging, and exercise on heart rate variability among male workers

OBJECTIVES: Effects of aging and leisure time physical activity (LPA) might influence the effect of occupational physical activity (OPA) on risk for cardiovascular disease (CVD). This study was conducted to determine whether OPA affects CVD after controlling the effects of LPA and other risk factors for CVD such as job stress. METHODS: Participants were 131 male Korean manual workers. Tests for heart rate variability (HRV) were conducted for five minutes in the morning at work. We defined OPA as the combined concept of relative heart rate ratio (RHR), evaluated using a heart rate monitor. RESULTS: Whereas high OPA was not related to any HRV items in the younger age group, high OPA was associated with an increased number of low-value cases among all HRV items in older workers. Exercise had beneficial effects only in the younger group. After controlling for exercise and other risk factors, the odds ratios of the root-mean square of the difference of successive normal R-R intervals (rMSSD) and high frequency band power (HF) among the older age and high OPA group compared with the younger age and low OPA group were 64.0 and 18.5, respectively. Social support and shift work were independent risk factors in HRV. CONCLUSIONS: OPA in aging workers increases CVD risks. This study provides support for the need for protection of aging workers from physical work overload, and indicates the need for further study of optimal limits of OPA.

Chronic and Acute Effects of Work-related Factors on Heart Rate Variability / 대한산업의학회지

OBJECTIVES: 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. METHODS: 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. RESULTS: 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. CONCLUSION: The physical and chemical environment, psychosocial stress and a physical workload may affect the autonomic nerve system.