Background: Changes in blood pressure and heart rate in smokers have been investigated in previous studies but far less is known about the cardiac autonomic response in smokers and according to best of our knowledge there is insufficient data especially in Northern India on effect of smoking on HRV (Heart Rate Variability). Therefore, we have taken up this study to assess HRV including the non linear HRV indices and HbA1c in non-diabetic, smokers and non-smokers. Methods: A total of sixty-two participants (including 30 male, non-diabetic, smokers of 20 to 40 years and 32 age matched, male, healthy non-smokers) were studied. Anthropometric variables were recorded. HRV was recorded and blood sample was sent for HbA1c and average blood glucose level. Results: We found a significant decrease in SBP (p=0.0001), DBP (p=0.0002), PR (p=0.0072), time domain parameters - mean RR (p=0.0001), SDNN (p=0.0001), RMSSD (p=0.0001) & pNN50 (p=0.0061), frequency domain parameters - TP (p=0.0002), LF (p=0.001) and HF (p=0.0002) and non-linear parameters - SD1 (p=0.0015) & SD2 (p=0.0023) in the study group. Cardiovascular and HRV parameters were negatively correlated with smoking index. Conclusions: Cigarette smoking impairs cardiac autonomic activity. We found a significant decrease in the time and frequency domain parameters of HRV which may be responsible for suppression of vagal tone and increased sympathetic activity. The pack years and smoking index were significantly associated with impaired cardiac autonomic activity and decreased HRV which may predispose to cardiac arrhythmias including sudden cardiac death. |