title: Effects of high occupational physical activity, aging, and exercise on heart rate variability among male workers.
abstract: OBJECTIVE
  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.
authors.affiliation: Department of Occupational and Environmental Medicine, Pusan National University Yangsan Hospital, Yangsan, Korea ; Environmental Health Center of Asbestos, Pusan National University Yangsan Hospital, Yangsan, Korea ; Medical Research Institute, Pusan National University Hospital, Busan, Korea ; Department of Preventive & Occupational Medicine, Pusan National University School of Medicine, Yangsan, Korea.
authors.forename: Dongmug
authors.initials: D
authors.lastname: Kang
authors.affiliation: Department of Occupational and Environmental Medicine, Pusan National University Yangsan Hospital, Yangsan, Korea ; Medical Research Institute, Pusan National University Hospital, Busan, Korea ; Department of Preventive & Occupational Medicine, Pusan National University School of Medicine, Yangsan, Korea.
authors.forename: Youngki
authors.initials: Y
authors.lastname: Kim
authors.affiliation: Department of Occupational and Environmental Medicine, Pusan National University Yangsan Hospital, Yangsan, Korea.
authors.forename: Jongeun
authors.initials: J
authors.lastname: Kim
authors.affiliation: Environmental Health Center of Asbestos, Pusan National University Yangsan Hospital, Yangsan, Korea.
authors.forename: Yongsik
authors.initials: Y
authors.lastname: Hwang
authors.affiliation: Department of Preventive & Occupational Medicine, Pusan National University School of Medicine, Yangsan, Korea.
authors.forename: Byungmann
authors.initials: B
authors.lastname: Cho
authors.affiliation: Department of Cardiology, Pusan National University Hospital, Busan, Korea.
authors.forename: Taekjong
authors.initials: T
authors.lastname: Hong
authors.affiliation: Department of Preventive Medicine, Kosin University Graduate School, Busan, Korea.
authors.forename: Byungmok
authors.initials: B
authors.lastname: Sung
authors.affiliation: Department of Preventive Medicine, Kosin University Graduate School, Busan, Korea.
authors.forename: Yonghwan
authors.initials: Y
authors.lastname: Lee
keywords: Cardiovascular disease; Exhaustion; Parasympathetic; Relative heart rate ratio; Social support; Vagal; Work limit; Workload