“Oral Health-related Quality of Life and Periodontal Status in Chronic Kidney Disease Patients: A Cross Sectional Study”

Background: Oral health-related quality of life includes the effect of factors such as oral health and oral function on people’s lifestyl es. Chronic kidney disease is caused by the deterioration of kidney structures, decreasing their function. CKD causes some oral problems, and these problems could affect people’s quality of life. This study was conducted to determine OHRQoL and periodontal health status in CKD patients. Methods: One hundred and four CKD patients participated in the study. Their OHRQoL was assessed by Oral Health Impact Profile-14 (OHIP-14), and their periodontal status was assessed by the community periodontal index of treatment needs (CPITN). The stage of the disease was measured by BUN and creatinine. We used t-test, ANOVA, and Pearson ’s and Spearman ’s correlation tests for statistical analyses. Results: The most frequent CKD stage was 5. The average total score of OHIP-14 in these patients was 14.82 (±4.86). The most frequent CPITN score was 2 (calculus). CPITN had a direct relationship with the total score of OHRQOL (P=0.004) and its physical domains (P<0.05). Conclusion: There was a significant relationship between periodontal status and OHRQoL in CKD patients. The quality of life in this group of patients might be improved by providing their periodontal treatment needs.


Introduction
Chronic kidney disease (CKD) is a progressive and irreversible situation, followed by renal structural demolition and functional decrease in three months or more, leading to the need for hemodialysis or kidney transplantation (1)(2)(3). The prevalence of CKD is increasing in developing countries. For example, death caused by CKD in Iran has been doubled from 1990 to 2010 (4). A meta-analysis in 2018 showed a higher prevalence of CKD in Iran than the global status (5). However, due to new treatments, the mortality rate in CKD has decreased, and there are more CKD patients with age-related oral morbidities (6).
CKD is categorized into five stages according to the glomerular filtration rate (GFR), ranging from >90% to <15% of kidney function. In the first stage, GFR is normal or increases slightly (>90%). Kidney damage is also probable. The patient does not have any symptoms, and the functional decrease is 10-20%. In stage two, GFR decreases slightly (60-89%). The third stage is defined by a moderate decrease in GFR (30-59%), and kidney function is halved. In stage four, severe GFR decrease happens (15-29%). At last, in stage five, kidney insufficiency occurs, and functional decrease is >75%, caused by damage of more than two million nephrons (GFR<15%) (7).
Patients with CKD usually experience impaired oral health, and periodontitis is one of the common problems in these patients (3,8). Iwasaki showed that periodontal disease indices were worse and higher in CKD patients than in the control group, and creatinine serum levels correlated with the severity of periodontal disease (9). Other oral and dental problems caused by CKD are decreased bone density, jawbone pain, metal taste, urea odor in the mouth, xerostomia, gingivitis, petechiae and ecchymosis, enamel hypoplasia, and temporomandibular joint problems (2,6,(10)(11)(12)(13).
Oral health-related quality of life (OHRQoL) is how oral health status impacts one's daily activities (13). Improving OHRQoL is considered the final achievement of various oral treatments (14). OHRQoL is measured via patient-centered approaches, consisting of questionnaires developed to assess the impact of oral health status or therapies on several aspects of life (15). These domains include functional, emotional, social, and psychological effects of oral health on the quality of life (16). Oral Health Impact Profile-14 (OHIP-14) is one of the questionnaires widely used to measure OHRQoL in systemic disease patients since it has exhibited acceptable discriminant ability and effectiveness regarding oral problems in these patients (11,17).
As CKD patients might suffer from several oral complications, OHRQoL might be impaired among them. A systematic review by Schmalz et al. concluded that OHRQoL is reduced in severe renal disease patients and mentioned the potential effect of oral health parameters of this phenomenon (18). However, Rodakowska et al. reported that subjective OHRQoL means might not reflect all the oral health problems in CKD, and the relationship between these variables and OHRQoL has yet to be established (14).
Moreover, geographical variables might determine factors associated with OHrQoL in CKD patients, too (13). Therefore, the present study aimed to evaluate OHRQoL and its relation to periodontal status in different stages of CKD in Isfahan, Iran.

Participants
The present cross-sectional study was carried out from May 2019 to February 2020.
Patients with a confirmed diagnosis of CKD, who were referred to the Nephrology Center of Al-Zahra Hospital, Isfahan University of Medical Sciences, Isfahan, Iran, were invited to participate in this study. Age>18 years, literacy, and willingness to be examined intraorally were the inclusion criteria. Patients suffering from hereditary syndromes or taking gingival enlargement-inducing drugs were excluded from the study.

Periodontal assessment
Periodontal status was examined with a dental mirror and a WHO probe under the light of the examiner's headlamp. CPITN index was used for periodontal assessment. In this index, each number is related to a specific periodontal status: 0 = healthy periodontal parameters, 1 = bleeding on probing, 2 = presence of calculus, 3 = 4-5 mm of pocket depth, and 4 = ≥6 mm of pocket depth. The whole dentition was divided into six sextants, with at least two functional teeth in each. Every single tooth was probed peripherally in six areas. The worst periodontal status of each sextant was considered representative for that sextant, and the worst sextant was considered representative for that patient's CPITN (19,20). A single examiner carried out the periodontal examination process in all the patients. Edentulous patients were excluded from this part of the investigation.

OHRQoL measurement
We used the Persian version of Oral Health Impact Profile-14 (OHIP-14) for evaluating OHRQoL. The validity, reliability, and accuracy of this questionnaire have been confirmed (21). OHIP-14 consists of 14 questions in 7 domains, and each domain consists of 2 consecutive questions. Each question is answered via Likert's 5-scale choices of frequency, ranging from 0 (never) to 4 (very often). To obtain the total score of every questionnaire, the scores of all the questions were summed up, adding up to a value between 0 and 56 (20). The score for each domain of the questionnaire was calculated as well.

Blood chemistry
Serum BUN and creatinine levels were collected from the patient's electronic medical records. Each patient's CKD was staged by determining the amount of GFR using the

Statistical analysis
SPSS 22 was used to analyze data. T-test, ANOVA, and Pearson's and Spearman's correlation tests were utilized. P<0.05 was considered statistically significant.

Results
One hundred four patients participated, with an age range and mean of 18-83 and 52.1 (±18.1) years, respectively. Table 1 shows the CPITN scores in both genders, and Table   2 shows the frequency distribution of CKD stages.

Tables 3. OHIP-14 mean domain scores and their correlation to CPITN (Spearman)
OHIP: Oral Health Impact Profile, CPITN: Community Periodontal Index of Treatment Need, SD: Standard Deviation

Discussion
Periodontal disease is one of the main problems in patients suffering from CKD (19).
Furthermore, it is becoming increasingly clear that periodontal disease can significantly impact OHRQoL in the general population (2). Based on the previous reports, the items with the greatest prevalence differences between periodontitis patients and healthy people are mainly related to psychological concerns, halitosis, pain, and aesthetics (2,11,14). However, the association between periodontitis and OHRQoL in patients suffering from CKD in Iran has not previously been explored. Thus, the present study adds new information to the literature.
The present study aimed to measure OHRQoL and periodontal disease in different stages of CKD and verify the possible correlation between these variables. According to the results, stages of CKD correlated with the severity of periodontal disease. In this regard, several other studies have revealed the correlation between periodontal status and CKD (2,10,(24)(25)(26). In addition, increased levels of inflammatory cytokines in CKD patients might exacerbate periodontitis (2).
The present study also found a significant association between CKD stages and OHIP-14 total score, indicating that the occurrence and severity of CKD affect the OHRQoL in this population. This finding is consistent with previous studies (2,24,(26)(27)(28)(29), confirming the accordance between objective and subjective measures of disease evaluation in these patients.
It should be noted that the correlation between OHIP-14 and CPITN scores was statistically significant. The same results have been reported by Pakpour et al., Oliveira et al., and Silva et al. (2,27,30). CKD patients lose more teeth due to a high prevalence of periodontitis among them (27). Besides, as the number of missing teeth is associated with speech problems, it can impair OHRQoL in CKD patients (29,31). Of note, more than a quarter of the study sample were edentulous, probably as a consequence of extremely poor past oral and periodontal health status.
On the contrary, some investigations found no significant (25,(32)(33)(34) or even opposite correlation between periodontal disease status and OHRQoL (35). Conflicting results in different communities could be due to their priorities and various perception of OHrQoL.
Various factors affect OHRQoL in the general population, and the situation is even more complicated in chronic systemically compromised patients (16). Developing diseasespecific questionnaires to assess OHRQoL in related populations probably ends up with more reliable conclusions in this regard. This investigation was carried out within the limitations of a cross-sectional study. The absence of temporal relation between variables results in an inability to clarify cause-andeffect analyses in such studies, leading to the controversial understanding of the conclusion. Of course, future studies with novel designs regarding oral health and its related quality of life in CKD will further elucidate the correlation between objective and subjective means of disease evaluation in these patients.

conclusion
In conclusion, there were significant relationships between CPITN and OHIP-14 total and functional limitation, physical pain, physical disability, and handicap domain scores in CKD patients. Thus, paying attention to periodontal treatment needs might improve oral health-related quality of life in these patients.

Availability of data and materials:
The datasets used and/or analysed during the current study are available from the corresponding author on reasonable request.