A Comparative Study of Heart Rate Variability in Smokers and Non Smokers

Smoking is an escalating public health problem especially in developing countries like India. It is a major risk factor for coronary artery diseases, cerebrovascular stroke, peripheral vascular diseases. Studies have shown that smoking increases the risk of myocardial infarction and sudden cardiac death. One of the mechanism by which smoking impairs the cardiovascular function, is its effect on Autonomic Nervous System control. There are several tests to determine the autonomic activity. Recently the most accepted tool is determining Heart Rate Variability. This study intends to evaluate the autonomic functions in cigarette smokers and non smokers. This is a case control study having a total of 100 male subjects -50 cigarette smokers (cases) and 50 non smokers (controls) in the age group of 25-35 years. Electrocardiography (ECG) was recorded in a quiet room with the subject in supine position after 10 minutes of rest. Analog ECG signal was converted to digital. Following parameters were taken -SDNN, RMSSD, pNN50, E: I ratio, LF(nu), HF(nu), LF/HF. Results were compared with the help of Student t test and the level of significance was fixed at p < 0.05. There was significant decrease in SDNN (p< 0.001), RMSSD (< 0.001), pNN50 (< 0.001), E: I ratio (p< 0.001), HF (p< 0.001) and significant increase in LF (p< 0.001), LF/HF (p< 0.001) in cases when compared to controls. This signifies higher sympathetic activity and decreased parasympathetic activity in smokers when compared to non smokers. The present study showed that cigarette smoking in males may affect the cardiac autonomic activity. There was a ift in the sympathovagal balance towards sympathetic predominance among cigarette smokers when compared to non-smokers.