According to the WHO, the tobacco epidemic is one of the greatest public health threats the world has ever faced. The death rate in the world is more than 8 million per year. More than 7 million of these deaths are due to direct tobacco use, and approximately 1.2 million are due to nonsmokers exposed to indirect smoking. Tobacco smoking is the most common form of tobacco consumption in the world. Other tobacco products include water pipe tobacco, various smokeless tobacco products, cigars, cigarillos, pipe tobacco, bidis etc. 1 Natives began using tobacco for pipes, cigars, and snuffs when Columbus and his successors recorded tobacco in other countries. As a result, Portuguese and Spanish sailors helped spread different types of tobacco for use around the world.4 Smoking is a major risk factor in the development of COPD and COPD-related peripheral neuropathy. 9 Grünberg Schaefer hypothesized the mechanism of why stress is associated with increased smoking. (a) Smoking reduces stress levels due to nicotine or other chemicals in tobacco reduces some aspects of stress.  (b)  Stress reduces the effects of nicotine, thereby Increasing the self- administration of nicotine, Stress-free situation; (c) Stress reduces the availability of nicotine, which leads to failure Withdrawal and consequent increase in tobacco consumption. (d) Smoking cigarettes (and Nicotine) Improves cognitive function affected by the harmful effects of stress Understanding. 13 Brainstem hypoxia, associated with COPD leads to the brainstem auditory evoked potential (BAEP) abnormalities, the functions of the eighth cranial nerve and brainstem were highly impaired in severe COPD.21 Smoking not only produces reactive oxygen radicals in smoke, but can also increase oxidative stress by weakening antioxidant defense systems. 28 Chronic smoking not only slows down the conduction velocity of sensory nerves, but also leads to oxidative stress in smokers. This effect is due to the reduction of total antioxidants in plasma volume. Oxidative stress can occur in smokers with impaired tobacco nerve conduction. 2

This study aims to observe the effect of oxidative stress on Brainstem Auditory Evoked Potential (BAEP) & to determine the status of oxidative stress in smokers and non-smokers.

The study was conducted in the Department of Physiology with collaboration department of Biochemistry of Career Institute of Medical Sciences & Hospital, Lucknow, Uttar Pradesh with intellectual assistance from Nims University Rajasthan, Jaipur. after obtaining ethical approval from the National Institute of Medical Sciences and Research, Nims University Rajasthan, Jaipur and also from Institutional Ethical Committee Career Institute of Medical Sciences and Hospital, Lucknow

This was a cross-sectional study. In this study, we recruited 100 adult males, who have been smoking tobacco for the last 5 years (≥2 pack years)133 with the age group of 25-55 years as Cases and age-matched 100 nonsmokers were also recruited after explaining the aim,

objectives and significance of the study, written informed consent is also taken. Anthropometric data, including age, height, weight, and BMI, were measured.

The Brainstem Auditory Evoked Potential (BAEP) testing was conducted in the Research Laboratory of the Department of Physiology at CIMS&H, utilizing the NEURO-STIM software (Medicaid system, Chandigarh, India), with default settings. Patients were positioned lying down, ensuring a relaxed and comfortable state, crucial for accurately detecting hearing thresholds during BAEP assessment. A cushion or pillow was placed beneath the neck to enhance patient comfort. The testing environment was maintained in a quiet condition, minimizing extraneous noise to facilitate optimal concentration on the test stimuli and masking noise. Electrode placement adhered to the International 10/20 System, utilizing a single-channel configuration. Electrode sites were cleansed with an abrasive cleanser or spirit before application. Conductive paste was then applied to the surface electrodes, positioned over the mastoid or ear (A1, A2) bilaterally, as well as on the forehead (Fz) and vertex (Cz). Monaural delivery of alternate (condensation and rarefaction) clicks through headphones occurred at a repetition rate of 11.1 clicks per second, with a stimulus intensity set at 80 dB (decibels). Both ipsilateral (Ai) and contralateral (Ac) ears of each subject were tested, with at least two recording trials conducted for each ear. A total of 2000 responses were averaged for each recording. Subsequently, brainstem auditory evoked potentials were recorded and analyzed. The identification of waves, including waves I, II, III, IV, and V was performed based on their standard characteristics.

Serum Malondialdehyde (MDA) was estimated from serum was done by a sensitive spectrophotometric method described by Buege et al. in 1978143. MDA in the catabolite of lipid peroxide can react with thiobarbituric acid (TBA) and produce red compound, which has a maximum absorption peak at 532 nm.

Serum Superoxide Dismutase (SOD) was estimated by using the Superoxide Dismutase Activity kit. All samples should be read off of the standard curve, which was created using a bovine erythrocyte SOD standard that was provided. In our uniquely coloured sample diluent, samples are diluted before being added to the wells.

The Xanthine Oxidase Reagent

is added after the substrate, and the mixture is then left to sit at room temperature for 20 minutes. In the presence of oxygen, the enzyme xanthine oxidase produces superoxide, which changes a colourless substrate in the detection reagent into a yellow-coloured product. At 450 nm, the coloured product is read. Superoxide levels drop and the amount of yellow product decreases as SOD levels rise in the samples.

Results were analyzed by using SPSS 29 Software.

Unpaired T-test was applied to analyze the statistical significance of changes in the BAEP and biochemical parameters. Pearson correlation was used to show the correction of oxidative stress with BAEP waves. p value <0.05 was taken as statistically significant.

Observation Table 1

The two-tailed P value is more than 0.05 in the ages of case and control groups. By conventional criteria, this difference is considered to be (p-value =0.11) and (t-value =1.59).

Total of 200 subjects were included in this study of which 100 cases (tobacco smokers) and 100 controls (non-smokers) Average age for the cases was 37.96 ±8.70 years and an average age of the control were 36.16 ±7.81 years and found statistically significant (p<0.05) Body Mass Index of cases (22.63±4.09) and of control subjects (25.12±3.60) was not found statistically significant (p<0.05)

Table 2

Descriptive Statistics for components of Blood Pressure and Arterial Pulse were described in Table 3. Systolic Blood pressure was observed to be significantly more (p<0.001) in cases (133.76±5.58 mm Hg) than control subjects (126.39±10.89 mmHg). Diastolic Blood pressure was observed to be significantly more (p<0.001) in cases (81.52±5.00mm Hg) than control subjects (77.10±6.13mmHg). No significant difference observed for the Arterial Pulse of cases (79.44±9.26) and control (80.19±9.03beats/min) with a p = 0.273.

Brainstem Auditory Evoked Potential (BAEP)

Brainstem Auditory Evoked Potential (BAEP) was observed in the control & case

groups with a sound intensity between 80 dB, and a comparison of the right and left ear was done separately.

Table 3. Right Ear Latencies and interpeak latencies between study groups

Latencies (msec.) of BAEP (Right Ear) wave I (1.66±0.07), II (2.84±0.11), III (3.87±0.13) and wave V (5.83±0.13) was significantly higher in tobacco smokers as compared to non-smokers wave I (1.54±0.02), II (2.66±0.07), III (3.64±0.08) and wave V (5.66±0.09). While wave IV (4.98±0.19) of BAEP of the case when compared with control (wave IV 4.92±0.20) did not show any statistically significance. Interpeak latencies (msec.) of Brainstem Auditory Evoked Potential (Right ear) IPL IIII (2.21±0.16), I IPL III-V (1.96±0.20), IPL I-V (4.17±0.14) was significantly higher in tobacco smokers as compared to Interpeak latencies of non-smokers IPL I-III (2.10±0.08), I IPL III-V (2.03±0.12), IPL I-V (4.14±0.09).

Table 4 Left Ear Latencies and interpeak latencies between study groups