Effects of smoking on heart rate variability in students (545.6)

The purpose of the present study was to investigate cardiac autonomic function in smokers and nonsmoker controls. Methods: Thirty nine light smokers (smoking less than 10 cigarettes a day) and thirty nine nonsmoking students with a mean age of 20.61±0.39 years take part in the study. Subjects were matched by sex, age, menstrual cycle phase and the level of anxiety. They were studied in the morning hours under standardized conditions, in a quiet room at a comfortable temperature. Time domain (SDNN, RMSSD, pNN50) and frequency domain (HF, LF and LF/HF ratio) parameters of HRV were obtained from all participants for 10 minutes while subjects were resting in a supine position. Statistical analysis was performed using Mann‐Whitney test. Results: In this study heart rate was found to be higher in smokers than in nonsmokers (74.08±1.31 vs 64.98±1.12 beat/min, p=0.000007). Time domain parameters were found to be lower in smokers than in nonsmokers (SDNN: 52.54±3.47 vs 72.74±5.35, р=0.0009; RMSSD: 47.68±4.37 vs 71.22±7.72 ms, p=0.009 and pNN50: 26.01±3.21 vs 39.49±3.85, p=0.01). Frequency domain measures were also significantly lower in smokers than non‐smokers (TP: 3498.94±487.42 vs 6527.34±986.47, p=0.005; VLF: 787.28±82.31 vs 1934.20±214.45, p=0.0003; LF: 1147.14±257.82 vs 1895.41±346.76, p=0.007 and HF: 1184.21±245.04 vs 2274.53±487.37, p=0.026). The other HRV parameters including LF/HF ratio, pLF and pHF were not significantly different. Conclusions: These results suggest that smoking has been associated with increased activity of the sympathetic nervous system and decrease in vagal cardiac control. This work was supported by the Ministry of Education and Science of the Russian Federation (grant 4.4904.2011, grant 14.B37.21.0215).