title: Depression and heart rate variability in firefighters.
abstract: BACKGROUND
  Depression has been found to increase the risk of mortality in patients with coronary artery disease through a mechanism of changing cardiac autonomic tone which is reflected by alteration of heart rate variability indices. This study investigated whether such mechanism existed in firefighters who were at high risk of depression and sudden cardiac death.
  
  
  RESULTS
  In total, 107 firefighters were recruited. All completed Beck Depression Inventory and underwent 24-h ambulatory electrocardiographic monitoring. The root-mean-square of successive differences, standard deviation of all normal-to-normal intervals index, and the percentage of differences between adjacent normal-to-normal intervals >50 ms were significantly lower in depressed than in non-depressed firefighters after controlling for hypertension, age, and body mass index (40.1 ± 18.8 vs 62.5 ± 77.4, p < 0.01; 63.0 ± 19.2 vs 72.1 ± 34.8, p < 0.01; 8.4 ± 7.2 vs 12.7 ± 10.9, p < 0.01, respectively).
  
  
  CONCLUSIONS
  Decreased vagal tone is a possible mechanism linking depression and sudden cardiac death in firefighters.
authors.affiliation: School of Medicine, University of Electronic Science and Technology of China, Chengdu, Sichuan, China.
authors.forename: Li-Mei
authors.initials: LM
authors.lastname: Liao
authors.affiliation: Acute andTertiary Care Department at University of Pittsburgh, Pittsburgh, PA, USA.
authors.forename: Salah S
authors.initials: SS
authors.lastname: Al-Zaiti
authors.affiliation: Strong Memorial Hospital, Rochester, NY, USA.
authors.forename: Mary G
authors.initials: MG
authors.lastname: Carey
keywords: Depression; firefighters; heart rate variability