A combination of lagged Poincaré plots and spectral characteristics were used to investigate the effect of
cigarette smoking on the autonomic nervous system (ANS). Heart rate variability (HRV) was determined
from pulse-to-pulse intervals (PPI) of ear photoplethysmography (PPG) waveforms. Spectral power analysis
of the pulse rate variability (PRV)was performed to determine lowfrequency (LF) and high frequency
(HF) components, and a lagged Poincaré plot was introduced to evaluate the nonlinear characteristics of
PRV. The correlations between lagged Poincaré plot and spectral power indices were studied in a group
of apparently healthy habitual cigarette smokers and compared to non-smokers. The width (SD1m) and
the length (SD2m) of lagged Poincaré plots significantly shrunk in the smokers for all lags (p < 0.05) except
SD14 and SD15. The results of this pilot study indicated that habitual smoking is associated with parasympathetic
withdrawal and augments sympathetic nerve activity. The results also demonstrated that the
combination of lagged Poincaré plots and spectral characteristics could show promise as a method for
distinguishing between different cardiovascular disease groups
