Reduced vagal cardiac control variancein exhausted and high strain job subjects

Abstract

Objectives: This paper has two primary objectives. First, the paper proposes methodological strategies for analyzing multiscale vagal cardiac control based on the Stress Disequilibrium Theory (SDT) using high frequency power of heart rate variability (HFP) and short term variance of HFP. Second, the paper provides evidence of reduced vagal cardiac control range and variability in high strain job and exhausted subjects. Materials and Methods: Job Strain was measured using the Job Content Questionnaire, 8/day diary reports, and a nationally standardized occupational code linkage in 36 healthy midaged males with varying strain jobs. Subjects were Holter-monitored for 48 hours, including a work and rest day. Subjects responded to questions on a daily diary as well as on the Job Content Questionnaire to test for exhaustion as a dichotomous state variable. Vagal cardiac control was measured by components of electrocardiograph: heart rate variability based measures of high frequency power (HFP). We assessed range of vagal cardiac control using extreme value analysis (data in upper tail); and short term vagal variability using Poincaré plots of HFP. Comparisons were made between high (N = 10) and low job strain (N = 22) jobs. Furthermore, subjects categorized as exhausted (N = 4) were separately analyzed. Results: Exhausted subjects displayed a reduced range of vagal cardiac control on the workday; and both high strain and exhausted stubjects displayed reduced short-term variance in vagal cardiac control. A repeated measures ANOVA controlling for age confirms reductions in variance of cardiac vagal activity in high job strain subjects (0.01), with further reductions in subjects reporting exhaustion (p = 0.001). Conclusion: This analysis supports the hypothesis that (a) job strain is associated with reductions in cardiac vagal -or system level -variance; and (b) that reduced system variability may be a characteristic of exhaustion.

QTc interval and electrocardiographic changes by type of shift work

“…Moreover, they are consistent with previous reports showing the contribution of low job control (decision latitude) to the pathophysiological deregulation, that can results in a significant contribution of autonomic nervous system to increase CVD risk [Collins et al, 2005;Collins and Karasek, 2010;Karasek et al, 2010].…”

Description of a large-scale study design to assess work-stress-disease associations for cardiovascular disease

“…Assessment of "exhausted response" in multiple-linked levels of physiological regulationwith clear physiological interpretation -poses a major challenge in data reduction, for which strategies are discussed below. The SDT provides potential insight into the meaning of variability of response in a self-regulatory context (i.e., it represents the variability of system-regulation intervention episodes), which can lead to new data analytic approaches for assessing variability, and even the "variability of the variability" [55]. …”

Can the job content questionnaire be used to assess structural and organizational properties of the work environment?

“…However, with respect to the present intentions and the normal usage of the JCQ, it is clear that the environmental circumstances that entailed machine-paced repetitive work were sufficiently homogenous as to be called identical work. The fact that it was possible to conduct the analyses in two highly homogenous study samples is a strength, and given that the JCQ is sometimes applied in study samples with far fewer participants (Collins and Karasek 2010;Collins et al 2005), the present study samples also appear sufficiently large.…”