title: Acute effects of cigarette smoking on the heart rate variability of taxi drivers during work.
abstract: OBJECTIVE
  This study attempted to clarify the acute effects of cigarette smoking on autonomic nervous function among taxi drivers under ordinary work conditions.
  
  
  METHODS
  Holter electrocardiographic recordings from 20 healthy middle-aged taxi drivers were analyzed for the time from 0800 in the morning to 0159 at night. The amplitudes (milliseconds) of the high-frequency (HF) component and the ratio of the low-frequency component to HF (LF/HF) were calculated as changes in the R-R interval, and time-course changes were investigated by a complex demodulation method. The exact starting time of smoking was identified with the use of a specially designed cigarette lighter. The mean LF/HF and HF for 5 minutes immediately prior to smoking were calculated as the baseline, and the means for every 5 minutes up to 15 minutes were calculated. The average values of these parameters for all of the cigarette smoking within the same time span of 0800-1659 and 1700-0159 were also determined.
  
  
  RESULTS
  The LF/HF significantly increased (P<0.05) within 5 minutes from the baseline immediately after smoking. This significant change in LF/HF was observed only at night. Although the interactive effect of the time of day on time course changes was not significant for the LF/HF or HF, the reactivity to increase LF/HF and decrease HF was more prominent at night.
  
  
  CONCLUSIONS
  Cigarette smoking significantly increased LF/HF within 5 minutes during ordinary taxi driving. Nighttime smoking seemed to have a more potent acute effect on the cardiac modulation of taxi drivers than in the daytime. The sympathomimetic and parasympatho-withdrawal response of smoking may play an additional role in increasing cardiac risk among taxi drivers.
authors.affiliation: Department of Health and Psychosocial Medicine, Aichi Medical University School of Medicine, Aichi, Japan. fumio@aichi-med-u.ac.jp
authors.forename: Fumio
authors.initials: F
authors.lastname: Kobayashi
authors.forename: Takemasa
authors.initials: T
authors.lastname: Watanabe
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Akamatsu
authors.forename: Hikari
authors.initials: H
authors.lastname: Furui
authors.forename: Teruyuki
authors.initials: T
authors.lastname: Tomita
authors.forename: Rumi
authors.initials: R
authors.lastname: Ohashi
authors.forename: Junichiro
authors.initials: J
authors.lastname: Hayano
mesh_terms: D000328:Adult; D001334:Automobile Driving; D015716:Electrocardiography, Ambulatory; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D016272:Occupational Health / Q000706:statistics & numerical data; D012907:Smoking / Q000503:physiopathology*; D013997:Time Factors; D017132:Workplace