Introduction

Halitosis is a common oral condition characterized by an unpleasant or offensive odor originating from the oral cavity. It is also commonly known as ‘bad breath’. Halitosis can occur in individuals of any age and sex, irrespective of their social status [1] and may cause profound societal shame and psychological impact [2]. Globally, many people suffer from halitosis. An estimated 31.8% of the general population (95% CI 24.6–39.0%) were found to suffer from halitosis in 2017 [3]. However, due to the lack of an accepted definition of halitosis, the subjective nature of reporting, and the different methodologies used, there is much heterogeneity in the reporting of its prevalence across the globe. In Bangladesh, the only study exploring halitosis was among women in Dhaka city, where the prevalence of halitosis was found to be 75% [4].

Halitosis may occur for various physiological and pathologic reasons [1, 5]. The foul-smelling morning breath of physiologic halitosis is caused by desquamated epithelial cells, stagnant saliva, and putrefaction of trapped food particles through the accumulation of bacteria. The pathological reasons involve local or systemic infections, chronic diseases, genetic problems, and metabolic failures [5]. However, some individuals may have halitosis but deny the same, while others have an exaggerated fear of halitosis (halitophobia) or may believe they have halitosis despite absence of such (pseudo-halitosis) [6]. Irrespective of the cause of halitosis, it should be diagnosed and treated by a dentist or physician as it is associated with significant personal discomfort and social embarrassment. [6] and decrease the oral health-related quality of life of the sufferers [7].

To differentiate between genuine halitosis from pseudo-halitosis and halitophobia, doctors often employ techniques like organoleptic measurement, gas chromatography, sulfide monitoring, and several other ways of chemical sensing [8]. People may present to the physician with complaints of halitosis when they develop a self-awareness of bad breath or when other complaints of bad odor coming out of their mouth. Consequently, self-perceived halitosis could impact a patient’s quality of life and lead to anxiety, reduced levels of self-esteem, and misinterpretation of other people’s attitudes [9].

Only a few research have investigated self-perceived halitosis among university students [10, 11] around the world. In Bangladesh, very few research explored self-perceived halitosis and fewer to none had been conducted among university students. Hence, although many studies have explored halitosis prevalence, little is known about halitosis perception among students in Dhaka, which this study aims to elucidate.

Methodology

Study design and population

This cross-sectional study was conducted among university students in Dhaka city using a convenience sampling method. The study included students from eight universities: North South University, Independent University, American International University Bangladesh, Dhaka University, Khilgaon Model College and University, Ahsanullah University of Science and Technology, State University of Bangladesh, and Jahangirnagar University. Data collection took place from November 1, 2021, to April 30, 2022. The study recruited participants who were permanent residents of Bangladesh with valid student ID cards from their respective institutions. Foreign nationals and individuals affected by mental illness were excluded from the study. The sample size was calculated using the formula for an unknown population: n = z2 × p × (1 − p)/d2; where: z = 1.96 for a confidence level of 95%, p = proportion (from Nazir et al.(2017) [12] = 75.1%), d = margin of error = 0.05. Considering the 10% non-response, the final adjusted sample size was 318 participants, who met the inclusion criteria.

Data collection tools

A semi-structured questionnaire was used to gather data from the study participants. This questionnaire was developed and modified during the initial one month period of the study by the researchers from the ones used in previous studies [11, 13, 14]. Initially, it was created in English and then translated into Bengali by different translators using a forward-backward translation process. The Bengali version was then face-validated by experts and pre-tested, with a Cronbach’s alpha score of 0.73. The questionnaire covered five domains: sociodemographic factors, lifestyle and behavioral factors, oral hygiene habits, dental problems, and parameters related to self-reported halitosis, with a total of 35 questions. The full questionnaire was designed to be completed in approximately 10–12 min.

Data collection procedure

Data was collected online using the Google Forms platform. The questionnaire was distributed digitally through various social media channels. One of the authors was responsible for sharing a secure link to the survey and reaching out to study participants who voluntarily agreed to take part by completing the consent form. Once all responses from the expected number of respondents were collected, the survey link was deactivated. The response rate for this study was 100% as all participants who were approached and met the eligibility criteria agreed to participate in the study and completed the questionnaire.

Variables of interest

The independent variables in this study included sociodemographic factors such as age, gender, height (in meters), weight (in kilograms), BMI, and marital status. Lifestyle and behavioral factors encompassed self-reported responses on smoking, alcohol consumption, sleep patterns, exercise, food habits, stress levels, tea/coffee intake, depression, mouth breathing, and anxiety.

For smoking status, ‘yes’ was defined as current daily smokers, ‘occasionally’ as current smokers who do not smoke daily, and ‘no’ as never smokers and past smokers (who had quit smoking at least one year prior). Similarly, for alcohol consumption, ‘yes’ was defined as individuals who currently consume alcohol, ‘occasionally’ as those who consume alcohol but not on a regular basis, and ‘no’ as individuals who have never consumed alcohol or have abstained for at least one year. Furthermore, stress levels were assessed as perceived stress described by the participant and measured using a single question with a 5-point Likert scale (options: “Not at all”, “Not much”, “A little”, “Very much”, “A lot”). Oral hygiene habits were assessed by examining practices such as tooth brushing, flossing, mouth washing, the use of toothpicks and miswak, tongue cleaning, mouth breathing, use of sugar-free chewing gum, and mouth fresheners. Dental problems considered in the study included participants’ self-reports of gum bleeding, gum swelling, tooth sensitivity, dry mouth, dental caries, tooth mobility, and food impaction. The dependent variable was self-perceived halitosis, categorized as either present or absent (yes or no).

Data management and analysis plan

Before conducting the analysis, all data were reviewed for completeness, outliers, and assumption violations. Descriptive statistics were used to summarize the socio-demographic characteristics of the participants and their self-perceived halitosis. Pearson’s Chi-squared test was used to examine the relationship between respondents’ characteristics and outcome variables. A multivariable logistic regression analysis was performed to investigate the connection between self-reported halitosis and various factors, including sociodemographic factors, lifestyle and behavioral factors, oral hygiene habits, and dental problems. We entered all the selected variables at once to build the multivariable logistic regression model. Variables that yielded complete separation across outcome categories were excluded from the multivariable analysis. The study reported adjusted odds ratios (AOR) and their corresponding 95% confidence intervals (CI). A p-value of less than 0.05 was considered statistically significant for all tests. The statistical analyses were carried out using STATA (Version 17).

Ethical considerations

All procedures were carried out in compliance with the ethical guidelines established by the Institutional Review Board (IRB)/Ethical Review Committee (ERC) of North South University (approval number: 2023/OR-NSU/IRB/0901). We followed the ethical principles outlined in the 1964 Helsinki Declaration and its subsequent amendments, or comparable ethical standards, as appropriate. Before starting the survey, every participant was required to complete the informed consent section. Participants were informed that their involvement was entirely voluntary and that they could withdraw at any time before submitting their signed consent. They were also assured that only the researchers would have access to the data, which would be reported at the group level without any personal identifiers. No personal data were collected. Throughout data collection and analysis, all data were handled with strict confidentiality and transmitted via a secure connection. Access to the questionnaire data was restricted to the research team only.

Results

Prevalence of self-perceived halitosis

Figure 1 illustrates the proportion of self-perceived halitosis among the study participants. The overall prevalence of Self-Perceived halitosis was 55.97% (Fig. 1).

Fig. 1
figure 1

Prevalence of self-perceived halitosis. (NB: data from a study conducted at universities in Dhaka city, Bangladesh)

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Socio-demographic variables

Among the 318 participants, the majority of respondents were between the ages of 22–28 years (82.70%) and were females (50.63%). Among those who had self-perceived halitosis (SPH), a significant proportion were females (74.53%). Within the age group of 29–35 years, 58.18% reported having SPH, whereas in the age group of 22–28 years, 55.51% reported having SPH. Additionally, a large proportion of participants with SPH were either overweight (61.00%) or obese (60.77%). Both sex and BMI were significantly associated with self-perceived halitosis (p < 0.05) (Table 1).

Table 1 Socio-demographic variables of the participants
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Lifestyle & behavioral factors

According to Table 2, it appears that the majority of the study participants were non-smokers (45.60%) and non-alcoholic (56.60%). However, among those who reported SPH, approximately 73% were occasional smokers. Similarly, about 71% of participants who consumed alcohol reported SPH. Furthermore, 63.33% of respondents who experienced SPH reported having either insufficient or not at all sufficient sleep. Additionally, a large proportion of participants who reported SPH were non-exercisers (66.29%), regular consumers of tea or coffee (61.35%), and consistent mouth breathers (approximately 65%). Moreover, among the participants who had SPH, 59.17% reported varying levels of stress (a little, a lot, or very much), 54.72% reported feeling anxious (yes or occasionally), 57.35% mentioned not consuming healthy food, and 60% reported having depression (yes or occasionally). Significant associations were observed between smoking, alcohol consumption, exercise habits, tea or coffee consumption, and mouth breathing with self-perceived halitosis (p = < 0.05).

Table 2 Lifestyle & behavioral factors
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Oral hygiene habit and self-perceived halitosis

The data depicted in Table 3 highlights that 85.71% of participants with SPH did not brush their teeth regularly or only brushed occasionally. Additionally, significant proportions of participants with SPH exhibited various other oral hygiene deficiencies: over 99% did not use a toothbrush, 94.74% did not use toothpaste, 75.76% did not use fluoride-containing toothpaste, 77.42% changed their toothbrushes after six months, and 60.85% did not use dental floss. Moreover, among the participants who had SPH, 76.14% did not clean their tongue or only cleaned it occasionally, 62.87% did not use toothpicks, more than 75% chewed gum regularly or occasionally, 58.87% did not use mouthwash or only used it occasionally, and 64.97% used mouth fresheners regularly or occasionally.

Statistically significant associations were observed between several oral hygiene practices—including brushing teeth, toothbrush use, toothbrush replacement, toothpaste use (both regular and fluoride-containing), dental flossing, tongue cleaning, toothpick usage, sugar-free chewing gum consumption, mouthwash application, mouth freshener usage—and self-perceived halitosis, all with a p-value of less than 0.05.

Table 3 Association between oral hygiene habits and self-perceived halitosis
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Dental problems and self-perceived halitosis

From Table 4, we can see that gum bleeding, gum swelling, dry mouth, dental caries, tooth sensitivity, and food impaction were associated significantly with self-perceived halitosis (p = < 0.05). From those with SPH: 76.85%had gum bleeding, 81.82% had swollen gums,72.50% had dry mouth, 67.78% had dental caries, 67.40% had sensitive teeth, and 64.13% had food impaction regularly or sometimes in their teeth.

Table 4 Association between dental problems and self-perceived halitosis
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Multivariable logistic regression analysis exploring factors associated with self- perceived halitosis

Table 5 provides insights from a multivariable logistic regression analysis investigating factors associated with self-perceived halitosis (SPH). The likelihood of experiencing SPH was 5.04 times higher in females compared to males (OR = 5.04; 95% CI: 2.01–12.62; p < 0.001). Participants who reported consuming alcohol were 7.35 times more likely to have SPH than those who did not (OR 7.35; 95% CI: 1.77–30.50; p = 0.006). Moreover, individuals who did not clean their tongue or only did so occasionally have 4.62 times higher odds of SPH compared to those who cleaned their tongue regularly (OR 4.62; 95% CI: 2.16–9.84; p < 0.001). Furthermore, participants who didn’t use sugar-free chewing gum exhibited a 0.25% lower likelihood of experiencing self-perceived halitosis compared to those who used it regularly or occasionally (OR = 0.25; 95% CI: 0.10–0.58; p = 0.001). Additionally, individuals with gum bleeding, either occasionally or regularly, were 7.43 times more likely to experience SPH than those without gum bleeding (OR = 7.43; 95% CI: 3.00-18.35; p < 0.001).

Table 5 Multivariable logistic regression analysis exploring factors associated
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Discussion

Self-perceived halitosis (SPH) represents a prevalent oral health concern transcending demographic boundaries [15]. Beyond its apparent social implications, SPH exerts considerable influence on individuals’ quality of life [16]. Particularly within the university milieu, where academic pursuits intertwine with social dynamics, the impact of SPH extends beyond mere discomfort, potentially affecting academic performance and interpersonal relationships [17]. Therefore, this study aimed to assess SPH and its associated factors among Bangladeshi university students.

Our study found that approximately 55.97% of the participants reported self-perceived halitosis. This finding is consistent with previous research conducted in India and Saudi Arabia among comparable populations, where the prevalence of self-reported halitosis ranges from 40 to 60% [14, 18]. Additionally, several former studies have investigated the prevalence of SPH, revealing varying rates across different regions and demographics. For instance, studies conducted in North America, Europe, Asia, and other regions have documented SPH prevalence rates spanning from approximately 20% to over 60% [19,20,21,22,23], highlighting the widespread nature of this oral health concern. Furthermore, research suggests that SPH is not confined to specific geographic regions or socioeconomic statuses but affects individuals across diverse populations globally [9]. In developed nations, estimates indicate a broad spectrum of oral malodor perception, with prevalence rates ranging from 8 to 50% [24]. This variability underscores the universal nature of the concern surrounding halitosis, regardless of geographical location or socioeconomic status.

One notable finding of the study was that females exhibited significantly higher odds of experiencing SPH compared to males. This aligns with previous research conducted by Su et al. [25]. and Kateeb [26], which indicates that females are more aware of and concerned about oral health issues, including halitosis, possibly due to gender roles and societal norms that socialize women to prioritize appearance and cleanliness. Furthermore, a cross-sectional study by Alzoman et al. [27]. demonstrates that hormonal fluctuations throughout the menstrual cycle and during pregnancy can affect oral health and breath odor perception, thereby increasing awareness of halitosis among females. Moreover, research by Lipsky et al. [28] and Mamai-Homata et al. [29]. suggests that women are more likely to engage in preventive oral health behaviors like regular brushing, flossing, and dental visits compared to men, making them more sensitive to changes in their oral health status. Recognizing and addressing these complex factors is imperative for devising comprehensive strategies to advance gender-inclusive approaches to promoting oral health.

The study unveiled a strong correlation between alcohol consumption and an increased propensity to report SPH, reinforcing earlier research by Oyapero et al. [30], which associates alcohol intake with diverse oral health issues, including halitosis. The primary mechanism behind this correlation is alcohol’s drying effect on the oral mucosa, which reduces saliva production. Reduced saliva creates an environment conducive to bacterial overgrowth and malodor formation [31, 32]. Additionally, research by Khan et al. [33]. and Poniewierka et al. [34]. shows that the high sugar and acid content in alcoholic beverages can exacerbate these issues by providing a food source for bacteria and altering the mouth’s pH balance. Moreover, prior literature documents lifestyle-related factors commonly associated with alcohol consumption, such as smoking and irregular dental care, which further compound these effects [35, 36]. This emphasizes the importance of recognizing alcohol’s role in SPH development and implementing targeted oral health interventions.

In our study, we identified the significant impact of poor tongue-cleaning habits on the increased likelihood of experiencing SPH. This correlation resonates with existing literature, underlining the crucial role of tongue cleanliness in averting the onset of bad breath, as outlined by Banotra et al. [37]. The tongue, serving as a reservoir for oral bacteria, food particles, and dead cells, provides an ideal environment for bacterial proliferation if not adequately cleaned. Consequently, neglecting tongue cleaning allows these microorganisms to thrive, leading to the production of volatile sulfur compounds responsible for halitosis [37]. Furthermore, research by Peng et al. [38]. and Santacroce et al. [39]. suggests inadequate management of oral bacteria can lead to a range of dental issues, including plaque formation, gum disease, and tooth decay, while specific bacterial strains are additionally associated with systemic health conditions such as cardiovascular disease and respiratory infections [38, 39]. By promoting and emphasizing proper tongue cleaning practices, oral health professionals can empower individuals to proactively combat halitosis and mitigate the risk of associated oral and systemic health issues.

An interesting finding emerged in the analysis of this study regarding the use of sugar-free chewing gum and its association with self-perceived halitosis (SPH). Contrary to expectations, participants who did not use sugar-free chewing gum exhibited a markedly lower likelihood of experiencing SPH compared to those who used it regularly or occasionally. Comparing our results with previous studies, which have generally indicated a positive relationship between sugar-free gum (SFG) usage and reduced halitosis, reveals a noteworthy discrepancy. For instance, studies by Shiyao et al. [40] and Al-Haboubi et al. [41] demonstrated that consistent use of SFG resulted in notable enhancements in Plaque and Gingival Index scores, reduced malodor levels, and improved self-perceived oral health. Similarly, a systematic review and meta-analysis by Nasseripour et al. [42] reported that chewing SFG, particularly xylitol SFG, for a designated period reduces the quantity of plaque in the oral cavity and decreases malodor levels in participants. Several factors may contribute to this unexpected association observed in our study. Firstly, it’s possible that participants who refrained from using SFG had established better oral hygiene practices overall, leading to a reduced likelihood of experiencing halitosis. Secondly, individual differences in oral microbiota and saliva composition could influence how SFG affects malodor perception. Additionally, variations in gum ingredients, flavorings, and usage patterns among different studies may also contribute to divergent findings. Further investigation is needed to elucidate the underlying mechanisms linking sugar-free gum usage to SPH.

Moreover, our analysis revealed a notable association between gum bleeding and self-perceived halitosis (SPH). Participants experiencing gum bleeding, whether occasionally or regularly, exhibited a higher likelihood of SPH compared to those without gum bleeding. This finding aligns with previous research conducted by Music et al. [43]. , which established a connection between periodontal disease, characterized by gum bleeding, and halitosis. Additionally, a systematic review by Memon et al. [44]. documented that individuals with periodontal disease are more susceptible to halitosis due to the presence of oral bacteria and inflammation in the gums. The association observed in our study suggests that gum bleeding may serve as a marker for underlying periodontal disease, which in turn contributes to the development of halitosis. This highlights the importance of addressing periodontal health as part of oral hygiene practices to reduce the risk of halitosis.

Limitations of the study

Firstly, our study was based on self-perceived halitosis and did not employ any objective measures of halitosis. By objective measures we could have find the accurate results which include like organoleptic assessment, Halimeter, and gas chromatography which are known as the main diagnostic methods to detect oral malodor but with a questionnaire in google form along over phone or without evaluation by healthcare providers, so it was impossible to determine the reliability as a result. Secondly, only university students within the capital city of Dhaka potentially affect the generalizability of the results to other university students outside the capital. Thirdly, the convenience sampling approach may limit the generalizability of the result to all university students. This non-random sampling method may introduce bias by primarily selecting respondents who are easily accessible.

Conclusion and recommendation

According to the research, we can conclude that Self-perceived halitosis is a problem for a considerable number of university students in Dhaka, Bangladesh. Sex, BMI, smoking, drinking alcohol, exercise, drinking tea/coffee, mouth breathing, tooth brushing, duration of changing toothbrush, toothbrush use, use of toothpaste, fluoride-containing toothpaste, dental floss, mouthwash, toothpick, sugar-free chewing gum, mouth freshener, tongue cleaning, gum bleeding, gum swelling, dry mouth, dental caries, tooth sensitivity, food impaction were the factors significantly associated with self-perceived halitosis. Nonetheless, an objective assessment is required to determine the prevalence of these findings. The role of dental professionals in maintaining excellent oral health should be highlighted in the community, and they should also be made aware of the various causes of halitosis, as the public is likely not fully aware of these causes and their management.