{'fraction_non_alphanumeric': 0.030050323508267432, 'fraction_numerical': 0.024083393242271746, 'mean_word_length': 4.7817955112219455, 'pattern_counts': {'":': 0, '<': 5, '<?xml version=': 0, '>': 3, 'https://': 0, 'lorem ipsum': 0, 'www.': 3, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Association between smoking and hearing status: a comparative study between smokers and non – smokers

Background: Smoking, age, gender, socioeconomic class and education may contribute to the hearing loss. In this study hearing loss between smokers (current and ex) and non smokers was compared. 
Materials and Methods: 145 smokers [79 current (68 males, 11 females) and 66 ex smokers (60 males, 6 females)] and 145 non smokers (69 males, 76 females) were studied. Modified Kuppuswamy scale and smoking index were used. Hearing loss was assessed by Audiometry. P value of<0.05(unpaired t test and chi square test) was taken as statistically significant. 
Result: Statistically significant and non significant differences were found between the mean age and educational status of current -ex smokers and smokers-non smokers respectively. Statistically significant and non significant differences were found between the socioeconomic status of smokers-non smokers and current -ex smokers respectively. Difference was significant between smoking index of current and ex smokers (p=0.003). 70.05% males had hearing loss as compared to females (49.46%). About 59.24% and 26.09% hearing loss cases belonged to low education and upper and upper middle social class respectively. 68% and 24.24% of moderate and severe smoking index were of professional to graduate educational status. 36.17% and 30.30% of moderate to severe smoking index belonged to upper and upper middle socioeconomic class. 73.91% were from low social classes. 47.59% non smokers and 25.51% smokers had no hearing loss. The severity of hearing loss was more in heavy smokers. 
Conclusion: Hearing loss associated with smoking was found to be more in male gender, advancing age, low socioeconomic and educational classes.


Introduction
There is a possible link between smoking and hearing impairment/ loss [1]. As per Meta Analysis conducted in Japan, 9 out of 15 observational studies have shown positive association between smoking and hearing loss [2]. Prevalence of smoking in the age group of 18-64 years is around 26.5% and 21.2% in males and females of same between age groups 15-49 years, overall smoking increases with advancing age. As per a survey in India, it was found that prevalence of smoking was more in low socioeconomic groups as compared to middle and high income groups. Similarly smoking was more prevalent amongst low education/ illiterate/ primary/ informal education groups [8].
A study conducted in 2002 showed that the smokers between 20-35 years of age were at higher risk of hearing loss than those above 35 years of age. In the same study it was found that the prevalence of conductive deafness was more between age group 20-68 years who smoked. Conductive deafness was reported in 6.1% of current and past smokers, moreover smokers were twice more likely to suffer from mild sensorineural deafness as compared to non smokers. With increasing pack years of smoking and age the risk of hearing impairment increases [9]. In contrast to studies which have reported association between smoking and hearing loss there are studies which have reported no correlation between smoking and hearing loss [10].
Further there are studies which have shown that women who are current smokers are likely to have hearing loss than men who are current smokers [11]. Thus, there are conflicting reports on association of hearing loss with smoking. The possible mechanisms of smoking induced hearing loss may be attributed to multiple factors like hypoxia induced by reduction in blood supply to cochlea and spiral ganglion due to vasospasm and atherosclerotic damage; nicotine induced damage of neurotransmitter receptors ;smoking induced oxidative stress and changes in vascularity of auditory system [12][13][14][15][16][17][18][19]. Smoking is influenced by socioeconomic factors and education [20]. Study has shown positive association of demographic variables like smoking status, gender, education with diseases including hearing impairment [21]. The present study was undertaken to find association between smoking and hearing loss. It also assessed the hearing loss in various socioeconomic and education class and also in male and female gender.

Materials and Methods
Subjects were grouped into smokers (current smokers and ex smokers) and non smokers (who have / had never smoked) categories after taking proper history. A smoker was defined as an individual smoking at least one cigarette per day. An ex smoker was one who had quitted smoking for at least 6 months prior to study. Non smoker was one who had never smoked. Both males and females were recruited in the present study. On the basis of smoking index the subjects were classified into never smokers, mild/light (1-100), moderate (101-300) and heavy (≥301) smokers.
The hearing tests were done in a sound proof room in OPD of ENT by Trained Audiologist and Speech Pathologist. The subjects were asked about smoking history, hearing problems. Using the audiometric data, subjects with hearing loss were classified as with mild (>25 decibel-≤ 40 decibel), moderate (>40 decibel -≤60 decibel) and severe (>60 decibel). Subjects were asked about their educational, socioeconomic status and residence (rural and urban). Socioeconomic and education class was analyzed using Modified Kuppuswamy Scale [22]. Smoking index was calculated by multiplying the duration of smoking (years) with average number of sticks smoked per day [23]. The external ear problem was assessed using Diagnostic Otoscope by Welch Allyn. Tympanometry was performed to assess middle ear problem. Audiometry was performed using Hughson Westlake Method. The audiometer used was of MAICO Company (Model MAY2).

International Journal of Medical Research and Review
Available online at: www.ijmrr.in 578 | P a g e

Study Bias: Referral bias
Study Size: Total 290 subjects participated in the study. Study included 145 smokers (79 current and 66 ex smokers) and 145 non smokers.

Statistical Methods:
The data was presented as mean ± SD. Data was analysed using SPSS 21.0. Unpaired t test and chi square tests were used to analyze the data. P value <0.05 was taken as statistically significant.

Results
As per Table 1 out of 145 smokers, 79 were current smokers and 66 were ex smokers. In current smokers 68 were males and 11 were females. Out of 66 ex smokers 60 were males and 6 were females. In145 non smokers, 69 were male and 76 were females. Statistically significant difference (p=0.008) was found between the mean age of current ( analysis of socioeconomic status found no significant difference between current and ex smokers (p 0.967) and significant difference between smokers and non smokers (p 0.001). In current and ex smokers subjects having rural and urban residence were 24, 55 and 45, 21 respectively (p significant at <0.001). In non smokers subjects belonging to rural and urban areas were 82 and 63 respectively. Statistically significant difference was found when smoking index of current and ex smokers were compared (p=0.003).  Table 5 shows that 69/145 non smokers i.e. 47.59% suffered from no hearing loss. But on other hand 25.51% (37/145) smokers reported no hearing loss. Statistically significant differences were found when hearing loss were compared between smokers and non smokers (p=0.001) and current and ex smokers (p<0.0010). Table 6 shows that severity of hearing loss measured in decibel in each category of smoking index. The difference was statistically significant (p<0.001). The percentage of subjects with no loss of hearing was more in non smoker category.

Discussion
Tobacco use has now reached the scales of epidemic. It is estimated that there are 1.1 billion consumers of smoked tobacco worldwide. The use of tobacco and tobacco related products is increasing worldwide specially in developing countries. 80% of smokers belong to low and middle income group. Owing to tobacco smoke environmental pollution and menace of second hand smoking is on rise [24]. Cigarette smoke contains more than 6000 Chemical Compounds, and both Free Radicals and Oxidants are present in abundance [25]. Direct and indirect inhalation of tobacco smoke has deleterious effects on heath. The prevalence of hearing loss is reportedly more in smokers as compared to non smokers [26]. Noxious stimuli lead to excess production of free

International Journal of Medical Research and Review
Available online at: www.ijmrr.in 581 | P a g e radicals in cochlea, which, in turn, affects hearing. In fact, cochlea is highly sensitive to nicotine, which disrupts auditory function pathway by interfering with cholinergic transmission and processing of auditory impulses [27,28].
Male gender and increasing age have been identified as risk factors for hearing impairment [29]. In our study we have found that number of male subjects with hearing loss was more as compared to females. The results may be attributed to multiple reasons. It has been observed that Men are more exposed to noise at work place, are more prone to smoking and other risk factors implicated in hearing impairment like hypertension [30].
In the present study we have found that mean age of the smokers was more than the non smokers. On the other hand hearing loss in smokers was more than that in non smokers. We also found that severity of hearing loss was more in smokers with higher smoking index. The results can be explained on the basis of earlier studies. Prasad BK et al found that with increase in smoking severity and pack years hearing impairment was more [31]. Paschoal CP et al studied the deleterious effects of smoking on hearing and concluded that harmful effects of smoking have direct relation with number of cigarettes smoked and indirect relation with age of the commencement of smoking [32]. Interestingly in our study we have found that non smokers were also having varying degree of hearing loss. It may be attributed to various reasons. Smokers are twice at risk of hearing loss as compared to non smokers. Although we have not studied the other causes of hearing loss but studies have shown that people exposed to second hand smoke are 1.94 times more likely to suffer from hearing loss [33]. Second Hand Smoke or environmental tobacco smoke impairs hearing by affecting outer hair cells [34]. Lalwani AK et al gave an interesting observation that hearing loss in adults may commence at an early age and also effects those who are exposed passively to smoking [35]. Age related hearing loss can be attributed to multiple factors like hypoxia, atherosclerosis, oxidative stress, dysfunction of mitochondrion and programmed suicidal death of inner ear cell [36].
In our study we have found that in ex smokers 60 subjects were having hearing loss as compared to 45 in current smokers. This means that ex smokers were having more hearing loss. This is in contrast with the study done earlier which have shown that current smokers are 1.73 times more likely to have hearing loss as non-smokers [37]. In our study also we have found higher number of smoker subjects with hearing loss than non smokers. But the possible explanation of ex smokers having more hearing loss than current smokers in our study could be attributed to the fact that in our study mean age of ex smokers was more than current smokers. Fabry DA et al found that in never and former smokers advancing age was a risk factor for hearing loss [38]. Interestingly, as written earlier that higher percentage of subjects with hearing loss belonged to low education and social class. Thus, it is inferred indirectly that hearing loss is more prevalent in low education and income class. The possible explanation could be that people with higher education are expected to be less exposed to occupational noise and thus are relatively protected from hearing impairment [40]. Pampel FC found that socioeconomic status and education have relation with smoking and its harmful effects. Income and education influence the smoking habits of individual. The people with low education usually have difference in awareness and perception of harmful effects of smoking as compared to those with higher education. Similarly, smoking in low socio economic class is often influenced by buying capacity and use of smoking as de stressor [41]. Studies have shown that low education, low income, male gender, urban residence are risk factors for hearing impairment [42][43][44].

International Journal of Medical Research and Review
Available online at: www.ijmrr.in 582 | P a g e

Conclusion
The subjects with more severity of smoking index have more hearing loss as compared to non smokers. There are various factors like gender, residence, socioeconomic and education which influence the harmful effects of smoking on auditory mechanism and effect hearing. The overall results can be attributed to knowledge, awareness and attitude towards the harmful effects of smoking on health. The results of study show that smoking does influence the hearing. There is a need to make the public aware about the harmful effects of smoking. Awareness campaigns are need of the hour. The results are showing that there is widespread distribution of smoking (current or ex) across every socioeconomic and education class. Lesser percentage of smoking in females may not be indicative of lesser problem of smoking in females. It may be due to low acceptance of smoking by females.

Limitations:
The present study was not done to identify the conductive /sensorineural or mixed hearing loss in smokers and non smokers. But identification of pattern of hearing loss will yield better results. The study if done on large scale will yield a better result. The identification of risk factors, estimating hearing loss in both smoked and smokeless tobacco users, considering occupational/ workplace exposure to noise and blood chemistry will yield better results.