Effect of noise stress on autonomic function tests

Abstract

The study was carried out in 200 male volunteers. They were divided into two groups. The study group was exposed to noise levels of more than 80 dB(A) for more than 8 hours a day for a period of 6 months, working in the steel and hammer industry, whereas the control group was working under normal conditions. The mean age of subjects was 33.33 + 0.867 years and the mean noise level to which they were exposed was 90.34 + 0.781 dB(A). Various autonomic function tests were carried out in both the groups and results were analyzed using Z test. Heart rate was recorded on cardiofax ECG machine and blood pressure (BP) was recorded using sphygmomanometer. The tests depicted significant increase in the mean resting heart rate and the heart rate response to standing (P=0.000), 30:15 ratio (P=0.002), the valsalva ratio (P=0.017), the % change in diastolic BP response to standing (P=0.000) and valsalva maneuver (P=0.000), the systolic BP and diastolic BP after cold pressor test (P=0.000) in study group as compared to the control group. The significant higher results in study group may be attributed to increased sympathetic activity. Thus, noise presents as a significant health hazard. It is recommended that maximum allowable duration of exposure should be reviewed and strictly followed.