Oral health-related quality of life and xerostomia in type 2 diabetic patients

Background. Diabetes mellitus (DM) is a known risk factor for xerostomia. Oral health-related quality of life (OHRQoL) is a multi-dimensional issue reflecting several effects of the oral condition on the quality of life. Objectives. The present study aimed to assess OHRQoL and its relationship with xerostomia severity in type 2 diabetic patients. Material and methods. A total of 200 patients participated in this cross-sectional study. The Xerostomia Inventory (XI) assessed xerostomia severity and the Oral Health Impact Profile-14 (OHIP-14) questionnaire evaluated OHRQoL. In addition, the fasting blood sugar (FBS) and glycated hemoglobin (HbA1c) tests were conducted, and the results were recorded, as well as the disease duration and denture wearing. Data analysis employed the t test and Pearson’s correlation coefficient. Results. The mean XI score was 22.27 ±6.92 and the mean OHIP-14 score was 13.76 ±8.41. The mean FBS, HbA1c and disease duration values were 161.23 ±49.14 mg/dL, 7.90 ±1.12% and 11.02 ±7.78 years, respectively. The OHIP-14 score correlated significantly with the XI score, age, FBS, HbA1c, the disease duration, and denture wearing ( p < 0.05). Conclusions


Introduction
Diabetes mellitus (DM) is a metabolic disorder typi cally characterized by the triad of polyphagia, polydipsia and polyuria. 1Most DM patients are elderly with type 2 disease. 2 Amongst miscellaneous side effects, oral health is severely affected by DM as a result of hyperglycemia, impaired healing, and qualitative or quantitative salivary alterations. 3,4Caries, oral burning, malodor, and peri odontal problems are the common comorbidities of xero stomia in these patients, and might influence their oral healthrelated quality of life (OHRQoL). 5erostomia is a subjective feeling of a dry mouth, and it can be caused by many local or systemic factors, including direct damage to salivary tissue. 6Several medical conditions may precede or exacerbate xerostomia, such as Sjögren's syndrome, systemic lupus erythematosus and sarcoidosis, as well as metabolic diseases, like DM. 7 Polyuria, dehydration and autonomic imbalance due to angiopathic disturbances have been proposed to underlie xerostomia in DM. 8 Regard less of its cause, xerostomia has extraordinarily detrimental effects on oral health.Rampant caries, periodontitis, and a re duced ability to chew or speak are significant side effects that can clearly influence a patient's OHRQoL. 9he OHRQoL score reflects the impact of the oral health status on several aspects of one's daily life.Oral health related quality of life is measured with the use of patient centered approaches.The OHRQoL score combined with clinical criteria constitute a suitable technique for evaluat ing oral treatment needs and outcomes. 10Means available to achieve such a goal are reliable questionnaires, validated for specific populations.The Oral Health Impact Profile14 (OHIP14) questionnaire is a popular tool in this regard, and it is applied in xerostomic and DM patients. 2][6][10][11][12] Molania et al. concluded that low medical control of type 2 DM resulted in hyposalivation as a side effect of the dis ease, and xerostomia affected the OHRQoL of DM pa tients in a negative way. 6Xerostomia is a significant oral side effect of DM that may interfere with the oral function of the patients suffering from the disease, resulting in poor OHRQoL among them. 2Therefore, evaluating the relation ship between xerostomia and OHRQoL in people with DM might help clinicians to prioritize the treatment planned for DM patients.The present study investigated OHRQoL and its relationship with xerostomia severity in type 2 DM patients.The null hypothesis of the present investigation was that there is no correlation between OHRQoL and xerostomia severity in type 2 DM patients.

Material and methods
The present analytical crosssectional study was con ducted between September 2020 and February 2021.

Ethical considerations
The local medical ethics committee at Isfahan University of Medical Sciences, Iran, approved the study protocol (IRI.MUI.RESEARCH.REC.1399.505).The patients were informed of the objectives of the investigation, the con fidentiality of the data, and that they could stop partici pating in the study at any time.They all provided written consent, and dental treatment was provided to them irre spective of whether they participated in the study or not.

Participants
Type 2 diabetic patients referred to the Department of Oral Medicine at the School of Dentistry of Isfahan University of Medical Sciences, Iran, were invited to par ticipate in the present study.
Patients who met the following criteria were included: a confirmed diagnosis of type 2 DM; and literacy suffi cient to fill out the questionnaires.
The exclusion criteria to minimize bias were the pre sence of any systemic diseases affecting the salivary glands, such as Sjögren's syndrome, alcoholism, a corticosteroid or hormone therapy, and a history of head and neck radio therapy/chemotherapy (Fig. 1).

Xerostomia evaluation
To measure xerostomia severity, the participants were asked to answer the questions in the Xerostomia Inventory (XI) (Table 1).The XI is composed of 11 questions regarding a dry mouth feeling, and the score for each question varies on a Likert scale from 1 to 5, with worse conditions scoring more, as follows: never -1; seldom -2; sometimes -3; often -4; and always -5.Therefore, xerostomia severity was reported as a sum between 11 and 55.The Persian version of the XI questionnaire was used, which was valid and reliable. 13

OHRQoL evaluation
Each patient was then asked to fill out the OHIP14 questionnaire, which consists of 14 questions measuring OHRQoL in 7 domains.The score for each question varies on a Likert scale from 0 (never) to 4 (always).As a result, the score for each section is a sum between 0 and 8, and the total score of the questionnaire ranges from 0 to 56.A higher score in this questionnaire indicates a lower OHRQoL.The Persian version of the OHIP14 question naire was used, which was valid and reliable. 14

Data collection
The patients' medical and dental records, as well as denture wearing, the duration of the disease, and the latest fasting blood sugar (FBS) and glycated hemoglobin (HbA1c) test values were recorded.Demographic data re garding patients' age and gender were also recorded and attached to the questionnaires.

Statistical analysis
The data was analyzed with IBM SPSS Statistics for Windows, v. 22.0 (IBM Corp., Armonk, USA), using rele vant statistical tests, with the t test used to compare the OHIP14 and XI scores between the gender groups.Pear son's correlation coefficient assessed the relationship be tween the OHIP14 and XI scores.The level of signifi cance was set at p < 0.05.

Results
Among more than 250 patients referred during the study period, 200 who fulfilled the eligibility criteria and gave informed consent participated in the study (Fig. 1).The mean age of the participants was 62.42 ±10.04 years, with 63.5% being female and 36.5% male.The mean FBS and HbA1c values were 161.23 ±49.14 mg/dL and 7.90 ±1.12%, respectively.The mean duration of the dis ease was 11.02 ±7.78 years.Denture (complete or remov able partial) wearers composed 45% of the sample.There was no missing data.
The mean XI score was 22.27 ±6.92, and the total and domain OHIP14 scores are shown in Table 2.There was a direct and statistically significant relationship be tween the XI and OHIP14 total/domain scores (Table 2).The relationship between the OHIP14 score and other study variables is shown in Table 3. Figure 2 shows that as the XI score increased, the total OHIP14 score also in creased, which translates into worse OHRQoL (p < 0.001; r = 0.444).

Discussion
Xerostomia is a side effect of type 2 DM that can have detrimental consequences on a patient's oral health. 2 The present study was conducted to evaluate OHRQoL in pa tients with type 2 DM and its correlation with xerostomia severity.The mean OHIP14 score was 13.86 ±8.41, which was relatively low, depicting a good OHRQoL.Moreover, a significant correlation was observed between the above mentioned variables.
Several studies have investigated OHRQoL in type 2 DM or other medically compromised patients.Similar to our results, Sadeghi et al. reported acceptable OHRQoL in Persian diabetics, 15 and HajianTilaki et al. reported a relatively good OHRQoL in Persian hemodialysis pa tients. 11Machado et al., 12 Pereira Oliveira et al. 10 and Verhulst et al. 3 came across even lower OHIP14 scores in diabetic patients in comparison with our study, reporting mean scores of 9.5 ±11.3, 5.37 ±4.95 and 2.5 ±5.2, respec tively.Of note, Hsu et al. 4 and Verhulst et al. 3 found lower OHIP14 domain scores as compared to our study.
On the other hand, Khalifa et al. 5 and Irani et al. 16 re ported no difference in the OHIP14 scores in people with DM vs. healthy controls.Meanwhile, Mohamed et al. re ported worse OHRQoL in Sudanese diabetic patients in comparison with the matched controls, 17 and Molania et al. reported a higher OHIP14 score than our results. 6eographical variances and miscellaneous under standings of OHRQoL might explain the differences in the overall health support given to patients in different countries and even cities in the same country, which may be in line with their socioeconomic status.
The OHIP14 questionnaire has proven to be a valu able tool for the subjective measurement of oral health in DM. 2 The present study showed a significant relation ship between the OHIP14 score and selfperceived xero stomia severity in diabetic patients, in line with studies by Nikbin et al., 2 Molania et al. 6 and AzoguiLévy et al. 18 These findings confirm its value and adaptation to other means of examining the clinical oral status.In fact, com bining the subjective means of need evaluation with the classic objective methods provides patients with the best remedies for improving their OHRQoL. 12ral healthrelated quality of life refers to both general and oral aspects of health. 2,3In the present study, the in dices related to the underlying disease (i.e., FBS, HbA1c, the disease duration, and age) and oral health conditions (i.e., the XI score and denture wearing) were significantly correlated with the OHIP14 score.In line with our re sults, Sadeghi et al. found direct correlations between the OHIP14 score and age and the disease duration in dia betic patients. 15n the contrary, Machado et al. 12 and Azogui Lévy et al. 18 reported that the elderly experienced better OHRQoL among people with DM.Meanwhile, Irani et al. concluded that the burden of medical conditions in dia betic patients (e.g., multiple drug consumption) deterio rates OHRQoL so heavily that oral health finds no room to show its impact; therefore, the underlying medical con dition seems to be a better predictor of OHRQoL than the oral health indices in diabetic patients. 16rom another point of view, several studies have high lighted the impact of oral health on OHRQoL in diabetics, especially regarding its physical domains.The present study found the most significant impact on the 'physical pain' domain, and the strongest correlation with the XI score was found for the 'functional limitation' domain (p < 0.001; r = 0.503).1][22][23] Since various factors potentially impact OHRQoL, including general and oral health parameters, planning treatment models to simultaneously improve general and oral health, as pro posed by Machado et al., 12 seems necessary for OHRQoL improvement in diabetic patients.

Limitations
Of course, this investigation was conducted within the limitations of a crosssectional study; therefore, detecting the exact effect of xerostomia on OHRQoL might have been confounded by other variables with an impact on OHRQoL.Future research is suggested, with case-control or other controlled studies, to more precisely investigate the impact of xerostomia or other specific oral health parameters on OHRQoL among diabetic patients in order to improve their quality of life.

Table 3 .
Relationship between the Oral Health Impact Profile-14 (OHIP-14) score and other study variables