Cross-Sectional Study on Proportions of Type 2 Diabetic Patients Presenting with Oral Candidal Lesions

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This study highlights the significant association between oral candidal lesions and type 2 diabetes mellitus patients, emphasizing the need for routine oral examinations, as all lesions were identified as incidental findings. These findings suggest that males, individuals older than 60 years, and denture wearers are at statistically significantly higher risk of developing oral candidal lesions. Clinically, this work can guide healthcare providers, particularly in diabetic care settings, to integrate oral health assessments into regular check-ups. Early identification of oral candidal lesions can lead to prompt treatment, minimizing potential complications and promoting overall oral health in this at-risk population.

Abstract

This study investigated the proportions and clinicopathological presentations of oral candidal lesions in type 2 diabetes mellitus (DM) patients attending the Diabetic Clinic at Teaching Hospital Peradeniya; Sri Lanka. A descriptive cross-sectional study was conducted on 355 DM patients aged over 18 years who had been receiving treatment for at least one year. Clinical photographs and periodic acid–Schiff (PAS)-stained cytological specimens confirmed diagnoses. Oral candidal lesions were found in 17.6% of patients; with Denture Stomatitis (4.0%), Erythematous Candidiasis (3.4%), Pseudomembranous Candidiasis (3.1%), and Chronic Hyperplastic Candidiasis (2.8%) being the most common types. Notably; all lesions were identified as incidental findings. Erythematous Candidiasis was more frequently noted among individuals older than 60 years (p = 0.041); while Denture Stomatitis was more common with higher glycemic levels (>140 mg/dL) (p = 0.045). Males were significantly more susceptible to oral candidal lesions (p = 0.002); except for Pseudomembranous Candidiasis and Denture Stomatitis; which were more frequent in females. Smoking (p = 0.005) and betel quid chewing (p = 0.008) were also identified as significant risk factors. Binary logistic regression revealed that males (OR = 3.160) and denture wearers (OR = 2.348) had a higher likelihood of developing oral candidal lesions. Despite the relatively low prevalence; routine oral examinations are recommended for early detection and management; ensuring better oral health in this at-risk population.

1. Introduction

Diabetes mellitus (DM) is a group of metabolic disorders characterized by chronic hyperglycemia due to defects in insulin secretion, insulin action, or both (American Diabetes Association, 2013). It is a global health challenge, with the International Diabetes Federation (IDF) reporting that 1 in 10 adults—approximately 537 million people—are living with DM (IDF, 2022). The disease disproportionately affects developing countries, particularly in South Asia, where the prevalence is rising. In Sri Lanka, the prevalence of DM is 9.8%, with an age–sex standardized prevalence of 21.8% [1]. Chronic hyperglycemia leads to long-term complications affecting various organ systems, including the retina, kidneys, nerves, cardiovascular system, and oral cavity [2]. Among the many complications of DM, oral manifestations are often overlooked despite their significant impact on quality of life. DM is associated with an increased risk of periodontal diseases, diabetic sialadenitis, xerostomia, burning mouth syndrome, oral candidiasis, and angular cheilitis [3]. Oral candidiasis is frequently observed in diabetic patients, especially those with poor glycemic control.

Candida species, which normally exist as commensals in the oral cavity, can become opportunistic pathogens under conditions such as immunosuppression, high salivary glucose levels, and reduced salivary flow, leading to the development of various oral lesions [4]. The most commonly isolated species in oral candidiasis is Candida albicans [5]. Candida spp. exhibit several virulence factors that contribute to their pathogenicity, including morphological switching, biofilm formation, adherence mechanisms, and environmental adaptability [6]. When transitioning from the yeast form to the filamentous (hyphal) form, C. albicans gains invasive properties, allowing it to breach mucosal barriers and cause lesions such as Pseudomembranous Candidiasis (PMC), Erythematous Candidiasis (EC), Chronic Hyperplastic Candidiasis (CHC), Median Rhomboid Glossitis (MRG), and Denture Stomatitis (DS) [7]. Studies indicate that the prevalence of oral candidiasis in DM patients ranges from 13.7% to 64%, with PMC being the most common presentation [8,9]. Despite extensive global research on DM-associated oral candidiasis, there is a notable gap in local data from Sri Lanka. To the best of our knowledge, no studies have specifically examined the prevalence and types of oral candidal lesions in Sri Lankan DM patients. This study aimed to address this gap by identifying the proportions of type 2 DM patients presenting with oral candidal lesions. Additionally, this study will raise awareness among affected individuals, allowing for early intervention and appropriate treatment. In this study, periodic acid Schiff (PAS) staining, a cost-effective and reliable method, was used to identify the hyphal form of Candida in oral mucosal lesions [10]. The findings will provide valuable insights for clinical practice, research, and healthcare professional training, ultimately improving the management of oral health in diabetic patients.

2. Materials and Methods

2.1. Study Design, Study Setting, and Sample Selection

A cross-sectional study was conducted to assess the proportions of oral candidal lesions in patients with type 2 DM and to explore the relationship between demographic factors, risk factors, and the development of such lesions. This study was conducted at the Diabetic Clinic of Teaching Hospital (T/H) Peradeniya and the Department of Oral Pathology, Faculty of Dental Sciences, University of Peradeniya. The study sample comprised of type 2 DM patients, both with and without clinically visible oral candidal lesions, attending the Diabetic Clinic at Teaching Hospital (T/H) Peradeniya. These patients were subjected to the following inclusion and exclusion criteria:

Inclusion criteria—Patients aged 18 years or older attending the Diabetic Clinic at T/H Peradeniya.

Exclusion criteria—Patients diagnosed with type 1 DM, type 2 DM patients who had undergone organ transplantation, and type 2 DM patients who were immunocompromised due to other conditions, including malignancies and autoimmune diseases such as systemic lupus erythematosus and rheumatoid arthritis.

Due to lack of data regarding the prevalence of oral mucosal lesions caused by Candida, a proportion of 64%, which is the prevalence of oral candidiasis in DM patients reported by Martinez et al., 2013 [5], was used as the reference value for sample size calculation. The sample size was determined to be 355 using Lamshow’s formula, as seen below.

$$n={\displaystyle \frac{p(1-p)\times Z^2}{l^2}};n={\displaystyle \frac{0.64(1-0.64)\times {1.962}^2}{{0.05}^2}}$$

p = 0.64, which is a proportion of candidiasis obtained from the study by Martinez et al., 2013 [5].

Z²= 1.96, which is a standard normal deviate value used to avoid an α error in two-sided tests.

l = 0.05, which is a level of precision.

An interviewer-administered data collection form was used to record the following: demographic details, medical history (duration of DM and the presence of other non-communicable diseases (NCDs)), risk factors (denture wearing, smoking, betel chewing, and alcohol consumption), and glycemic levels. For clinical confirmation, photographs of identified oral lesions were taken and documented.

2.2. Cytological Sample Collection and Staining Protocol with PAS

Once the patients gave consent, they were requested to rinse their mouths for 20 s to remove debris. Thereafter, all oral mucosal surfaces were visualized using a mirror. Once oral lesions suspected to be candidal lesions were observed, sterile cotton buds were placed firmly against the candidal lesions and rotated 4 to 5 times to collect the cytological specimens. Thus, the cytological samples obtained were spread on labeled glass slides, fixed in 95% ethanol for 10 min, and air-dried. Thereafter, slides were stained with periodic acid–Schiff stain (PAS) (Biomarq Life Sciences Private Limited, Hyderabad, India) as mentioned below. Additional swabs were taken from the impression surface of dentures belonging to DS patients.

The PAS staining protocol was as follows: The fixed cytological smears were first hydrated. A 1% periodic acid–Shiff solution was applied and allowed to act for five minutes. Following this, the slides were rinsed under running tap water for three minutes and subsequently washed with distilled water three to five times. Schiff’s reagent was then applied, and the slides were incubated for 10 to 15 min. After incubation, the slides were rinsed under running tap water for three to five minutes until a magenta color developed, indicating the presence of periodic acid–Schiff-positive components. Counterstaining was performed using hematoxylin to allow visualization of the nuclei, and the slides were rinsed again under running tap water until the nuclei appeared blue. The staining was enhanced with a final rinse under running water. Finally, the slides were air-dried and mounted for microscopic examination. Once the staining protocol was completed, the slides were visualized under a light microscope at the scanning power (×4 magnification), and the adequacy of the smear was determined by identifying >50 epithelial cells. Thereafter, under high magnification (×40), magenta-colored fungal hyphae were identified and recorded. However, in most lesions, the yeast form of Candida was also identified; only lesions with hyphae were determined to be attributed to Candida, as it is the pathogenic form capable of producing disease. Appropriate negative (smear from a healthy individual) and positive controls (smear from a diagnosed patient with Pseudomembranous Candidiasis) were used to determine the accuracy of staining and as a reference to identify candidal hyphae.

The methodology is summarized in Figure 1.

2.3. Statistical Analysis

Data were analyzed by using SPSS (Statistical Package for the Social Sciences). For statistical analysis, the distribution of quantitative data was assessed and found to be non-normally distributed. Consequently, non-parametric tests were employed. The chi-square test was used to evaluate the association between oral candidal lesions and socio-demographic and risk factors. Binary logistic regression was subsequently conducted to further explore these associations. The Mann–Whitney U test was applied to compare quantitative variables across different types of oral candidal lesions. A p-value of <0.05 was considered significant. The rationale and statistical tests employed in this study are summarized in Figure 2.

2.4. Methodology Overview

A cross-sectional study was conducted among 355 type 2 DM patients at the Diabetic Clinic, Teaching Hospital Peradeniya. Patients were clinically screened for oral candidal lesions, which were confirmed via exfoliative cytopathology and PAS staining. Demographic data and risk factors were collected using an interviewer-administered form. Non-parametric tests (chi-square and Mann–Whitney U tests) and binary logistic regression were applied using statistical package for the social sciences-26th version (SPSS), IBM Corp, New York, USA, with significance set at p < 0.05.

3. Results

The mean age of the study population was 60.38 years (SD ± 10.36), ranging from 29 to 86 years. The majority (50%) were over 60 years old. There was a female predominance (67.6%), with a male-to-female ratio of 1:2. The ethnic distribution predominantly consisted of Sinhalese (84.1%), aligning with the general population of the Kandy District. Fifty-five percent (55.1%) of participants were diagnosed within the last decade. Additionally, 54.8% were also receiving treatments for hypertension and dyslipidemia, while 26.7% only had type 2 DM. Figure 3 presents the detailed socio-demographic features of the study population.

Candidal lesions were identified in 17.6% of the study population (62/352 patients), with the diagnoses confirmed through identification of fungal hyphae with exfoliative cytology using PAS staining. The most common lesion was Denture Stomatitis (DS) (4%) (Figure 4), followed by Erythematous Candidiasis (EC) (3.4%), Pseudomembranous Candidiasis (PMC) (3.1%) (Figure 5), and Chronic Hyperplastic Candidiasis (CHC) (2.8%) (

Table 1. Clinico-pathological presentation of commonly observed candidal lesions.

Lesions	N (%) [Out of 63 Lesions]	Site		* Median Age in Years	Gender		* Median Glycemic Level (mg/dL)
					Male	Female
PMC	11 17.5%	Dorsum of the tongue Buccal mucosa	8 3	62	5	6	137
EC	12 19%	Dorsum of the tongue Buccal mucosa Hard palate Soft palate	7 3 1 1	67	7	5	160
CHC	10 15.9%	Buccal mucosa Alveolar mucosa Lip	8 1 1	61.5	8	2	152
DS	14 22.2%	Hard palate	14	60.5	3	11	148

Note: PMC = Pseudomembranous Candidiasis; EC = Erythematous Candidiasis; CHC = Chronic Hyperplastic Candidiasis; DS = Denture Stomatitis. * Due to non-normal distribution of data, median value was used to obtain a meaningful representation instead of mean value.

). Less frequently identified conditions included Angular Cheilitis (AC) (1.1%), Candida-associated dry mouth (0.6%), and Median Rhomboid Glossitis (MRG) (0.3%), which were excluded from further clinicopathological analysis due to their low prevalence. A noteworthy finding was that all DM patients (100%) were unaware of the existence of their oral lesions, which were detected as incidental findings during this study.

PMC (72.7%) was predominantly found on the dorsum of the tongue, with a slight female predominance (male-to-female ratio of 0.8:1). The median glycemic level in this group was 137 mg/dL. EC had the highest median age (67 years) and median glycemic level (160 mg/dL). Unlike PMC, EC was more prevalent in males (male-to-female ratio of 1:0.7), but similarly, most lesions (58%) were on the dorsum of the tongue. CHC showed higher median glycemic levels (152 mg/dL) than PMC (137 mg/dL) and was mostly located on the buccal mucosa. DS, the most common lesion, was significantly associated with upper denture wearers and was exclusively found on the hard palate (100%). It was more frequent in females (male-to-female ratio of 0.27:1) (Table 1). Patients with EC were significantly older compared to those without candidal lesions (p = 0.041, Mann–Whitney U test). DS patients had significantly higher glycemic levels than those without lesions (p = 0.045, Mann–Whitney U test), highlighting the impact of hyperglycemia on DS occurrence in denture wearers.

According to

Table 2. Comparison of clinicopathological presentations of patients with and without candidal lesions.

Feature	DM with Candidal Lesions (n %)	DM Without Candidal Lesions (n %)	X2 Test p Value
1. Age in years ≤60 ≥61	26 (7.38) 37 (10.51)	148 (42.04) 141 (40.05)	0.153
2. Gender Male Female	31 (8.80) 32 (9.09)	83 (23.57) 206 (58.52)	0.002
3. Race Sinhala Tamil Muslim	54 (15.34) 5 (1.42) 4 (1.13)	242 (68.75) 20 (5.68) 27 (7.67)	0.73
4. Duration following diagnosis in years ≤15 ≥16	44 (12.5) 19 (5.39)	227 (64.48) 62 (17.61)	0.173
5. Relationship with other NCDs DL + HTN Other NCDs present No other NCDs	36 (10.22) 12 (3.40) 15 (4.26)	157 (44.60) 53 (15.05) 79 (22.44)	0.848
6. Glycemic level (mg/dL) ≤110 ≥111	16 (4.54) 47 (13.35)	89 (25.28) 200 (56.81)	0.396

, males were significantly more likely to present with oral candidal lesions (27.19%) compared to females (13.44%, p = 0.002, χ² test). Patients older than 60 years had a higher prevalence (10.51%) of candidal lesions than those younger than 60 years (7.38%); this was not statistically significant (p = 0.153, χ² test). Higher glycemic levels (>110 mg/dL) were associated with a greater likelihood (13.35%) of candidal lesions compared to those with lower glycemic levels (<110 mg/dL, 4.54%); however, this was not statistically significant. The presence of other NCDs (e.g., hypertension and dyslipidemia) was more common (10.22%) in patients with candidal lesions than in those with DM only (4.26%); this was not statistically significant (p = 0.848, χ² test).

Table 3. Association between risk factors of DM patients and occurrence of oral candidal lesions.

Risk Factors	DM with Candidal Lesions (n%)	DM Without Candidal Lesions (n%)	X2	df	p
1. Denture Denture wearer Non-denture wearer	21 (33.33) 42 (66.7)	73 (25.3) 216 (74.7)	1.723	1	0.189
2. Smoking Present Absent	14 (33.3) 28 (66.7)	49 (15.8) 261 (84.2)	7.733	1	0.005
3. Betel chewing Present Absent	21 (28.4) 53 (71.6)	42 (15.1) 236 (84.9)	7.004	1	0.008
4. Alcohol misuse Present Absent	13 (23.6) 42 (76.4)	50 (16.8) 247 (83.2)	1.461	1	0.227

presents the association between different risk factors and oral candidal lesions. Smokers had a significantly higher prevalence of candidal lesions (22.2%) compared to non-smokers (9.7%, p = 0.005, χ² test). Betel chewers were significantly more likely to have candidal lesions (33.33%) than non-chewers (18.33%, p = 0.008, χ² test). Alcohol consumption was not identified as a significant risk factor for candidal lesions (p = 0.227, χ² test). Male sex was associated with a 3.16 times higher risk of developing oral candidal lesions (OR = 3.16, 95% CI: 1.713–5.828). Denture wearing significantly increased the risk of developing oral candidal lesions (OR = 2.348, 95% CI: 1.240–4.447).

4. Discussion

This study addresses a significant research gap regarding the prevalence of oral candidal lesions in type 2 DM patients within a specific demographic area. While the general population may also experience such lesions, focusing on DM patients is crucial, as integrating this knowledge into their management protocols can improve clinical outcomes. Our study observed all recognized and previously described oral candidal lesions, including PMC, EC, CHC, DS, AC, MRG, and Candida-associated dry mouth. Surprisingly, only 17.6% (Table 1) of type 2 DM patients exhibited Candida-related mucosal lesions, which is a lower prevalence than expected. An extensive literature review did not identify comparable studies focusing exclusively on oral candidal lesions in DM patients. Instead, our findings were compared with studies examining oral Candida carriage rates, which range from 13.7% to 81% in DM patients [5,11], and studies evaluating specific oral candidal lesions. A Sri Lankan study reported an oral Candida carriage rate of 81%, with 33% of patients having counts exceeding 2000 CFU/mL [11]. Martinez et al. highlighted challenges in diagnosing Candida-induced lesions without the detection of pathogenic hyphae in exfoliative cytology [5], which was a challenge also encountered in our study. A statistically significant male predisposition was observed among patients with oral candidal lesions, aligning with studies conducted in India and Saudi Arabia [12,13]. However, Sampath et al. [11] reported a female predilection for Candida carriage in Sri Lankan DM patients. This discrepancy may be due to the higher prevalence of risk habits such as smoking and betel quid chewing among males in our study sample. Interestingly, previous studies have also indicated a higher proportion of infection-free individuals among males [14], suggesting that risk behaviors rather than gender alone may contribute to the observed differences.

Denture Stomatitis (DS) was the most frequently identified Candida-associated lesion, affecting 4.0% of type 2 DM patients. Among them, 21.42% were males and 78.58% were females. Previous systematic reviews and meta-analyses reported a higher DS prevalence (10–67%) in DM patients [15]. The lower prevalence in our study may be attributed to good denture hygiene practices among participants. However, among patients in whom DS was diagnosed, a notable lack of denture hygiene awareness was observed. Similar female predominance in DS cases has been reported in India [16], whereas Javed et al. found a higher prevalence of Candida albicans carriage in denture-wearing males [17]. A significantly higher median glycemic level was identified in DS patients compared to those without lesions. This aligns with previous studies [18,19] that highlight the correlation between hyperglycemia and increased Candida colonization. Regarding the clinical presentation of DS, our study revealed 21.4% and 78.6% of Newton type 1 and type 2 lesions, respectively. Similar to the previous literature, the majority of DS lesions identified in our study were Newton type 2 lesions. However, in contrast to the available literature, where the majority of Newton type 2 lesions were associated with symptoms, all of our DS patients were asymptomatic, and the lesions were diagnosed as incidental findings [20,21].

Erythematous Candidiasis (EC) was the second most common lesion in our study. The literature suggests that DM patients wearing dentures are at risk of developing EC [22]. Other risk factors include antibiotic and inhaler use [23]; however, such practices were less common among our participants, possibly contributing to the lower EC prevalence. A statistically significant age difference was observed between EC patients and those without lesions (p < 0.05; mean rank with EC: 201.25; mean rank with no lesions: 148.97). While no prior studies have reported this finding, our results suggest a higher likelihood of EC development in elderly DM patients, emphasizing the need for clinician awareness for early diagnosis and management.

There are studies that indicate a high prevalence (38%) of PMC among DM patients with oral candidal lesions [5]. PMC is commonly associated with immunocompromised states, including DM [24]. The relatively lower prevalence in our study may be attributed to effective DM management at the Diabetic Clinic at T/H Peradeniya and the exclusion of DM patients with other immunosuppressive conditions. CHC is a controversial entity due to its potential for malignant transformation [25]. Our study identified a relatively higher proportion of CHC cases in DM patients compared to a previous study [25], likely due to additional risk factors such as smoking and betel quid chewing in our study population. Diagnosing CHC solely based on clinical and cytological findings poses challenges, as distinguishing it from leukoplakia with Candida superinfection requires biopsy confirmation. This limitation may have resulted in an overestimation of CHC cases in our study. Only 1.1% of DM patients in our study presented with AC, which is a significantly lower prevalence than the 14.1% reported in an Indian study [16]. This suggests that DM alone is not a primary risk factor for AC, which is influenced by additional factors such as vitamin deficiencies, reduced occlusal vertical dimension, and bacterial co-infection [26]. Cytological samples from our AC patients confirmed a high bacterial colonization rate, supporting the multifactorial etiology of this lesion.

More than half (53.96%) of oral candidal lesions occurred in patients older than 60 years. The literature suggests that individuals of older age are more susceptible to oral candidiasis [27]. Studies show a significantly higher Candida prevalence in adults aged 56–92 years [28] and an increased colonization rate in diabetic patients over 40 years [29]. The age distribution in our study aligns with these findings, reinforcing the need for heightened clinical vigilance in older DM patients. Studies suggest a positive correlation between glycemic levels and Candida colonization [18]. In our study, 47 out of 63 patients with oral candidal lesions had fasting blood glucose levels exceeding 110 mg/dL. However, other research indicates that glucose concentration alone does not affect Candida albicans’ invasive behavior [30], suggesting that additional risk factors contribute to lesion development.

A statistically significant association between smoking and Candida lesions was observed. Studies in Iran reported a dose-dependent relationship, with increased cigarette consumption correlating with higher oral candidiasis risk [31]. A Sri Lankan study also found a significant association between smoking and oral Candida carriage in DM patients [5]. Smoking-related alterations, such as reduced salivary flow, lowered salivary pH, and decreased immunoglobulin A levels, contribute to increased Candida colonization [31]. A notable association was found between betel quid chewing and Candida-associated lesions. A Thai study reported elevated Candida levels in betel quid chewers [32]. Further research in Bangladesh linked betel chewing to hyperglycemia in DM patients, potentially influencing Candida carriage and lesion development [33]. However, a contrasting study found no significant effect of betel quid chewing on Candida carriage [34].

5. Conclusions

The relatively lower prevalence of oral candidal lesions observed in our study suggests that effective glycemic control and medical management may play a protective role in DM patients. However, the higher risk among males and denture wearers highlights the need for targeted interventions in these subgroups. Early detection and timely management of oral candidal lesions are essential to improving overall health outcomes and quality of life in this vulnerable population. Routine oral health assessments, oral screenings, and oral health education should be incorporated into diabetes management protocols to facilitate early detection and timely treatment of oral candidal lesions in diabetic clinics.