Oral health factors related to the quality of life in elderly urban residents of South-West Poland

Background The process of human body ageing is an inevitable phenomenon affecting all organs. Hence, the concept of Oral Health-Related Quality of Life (OHRQoL) was introduced, based on the denition of health developed by WHO. The study aimed to evaluate the impact of selected oral health parameters on oral health-related quality of life in elderly residents of South-West Poland. Methods The study involved 500 participants who were the citizens of South-West Poland aged 65 and more. There was an oral examination performed, including the assessment of coronal and root caries, periodontal disease, dental prosthetic status and xerostomia. The impact of oral health-related quality of life was measured using the Oral Health Impact Prole-14 (OHIP-14). Furthermore, socio-demographic questionnaires were obtained from participants. Logistic bivariate and multivariate regression analyses of dependent variables and independent variables were carried out as part of the study.


Background
In recent years, there was an increase in the number of the ageing population on a global scale, particularly in developed countries. [1]The process of human body ageing is an inevitable phenomenon affecting all organs. Age-related changes occurring in the oral cavity include teeth, periodontium, mucosa, maxillae, temporomandibular joints, as well as salivary secretion. [2] Oral health signi cantly affects the overall quality of life. It has been identi ed as an integral component of general health which, when compromised, deteriorates the overall health and quality of life. [3] The impact is extensive; it leads to decreased activity of daily life and results in poor physical and/or mental well-being. Therefore, the concept of Oral Health-Related Quality of Life (OHRQoL) was introduced, based on the WHO de nition of health de ned as a state of physical, mental, and social well-being and not merely the absence of diseases or disability. [4][5][6][7] The relation between oral health and the quality of life may be determined by evaluating the extent to which oral health affects the said quality of life by ful lling functions such as the ability to chew, bite, swallow, and speak, mental well-being (satisfaction with the appearance of one's own teeth, self-esteem), physical well-being (feeling comfortable eating, not feeling any discomfort or pain), and social well-being (feeling comfortable speaking to others). One of the most frequently applied international assessment instruments -the Oral Health Impact Pro le (OHIP) scale -consists of 49 questions, while its shortened version includes 14 questions (OHIP- 14). The shortened version addresses the issue of functioning, physical and psychological pain, as well as social and physical disabilities. [8] The study aimed to evaluate the impact of selected oral health parameters on oral health-related quality of life in elderly residents of South-West Poland.

Methods
The presented observational study was carried out as part of the project "Oral health and quality of life within old ages -a cross sectioned study in Germany and Poland" in cooperation between Municipal Council and the University Hospital Carl Gustav Carus in Dresden, Germany. The study was supported with funds from the Municipal Council as part of the project "Stan zdrowotny jamy ustnej a jakość życia osób w wieku starszym z Wrocławia" (Oral Health and the Quality of Life of Elderly Residents of Wrocław) ( nancial agreement P/ZJU/1/2015-2017).
The STROBE guidelines (Strengthening the Reporting of Observational Studies in Epidemiology) were followed. [9] The study involved randomly selected participants (n = 1338), both males and females, aged between 65 and 99. (Fig. 1). All participants were citizens of Wrocław -Poland's fourth-largest city and the capital of the Viovodship of Lower Silesia, the most urbanized region in Poland.
The inclusion criteria included: age -65 and more, place of living (local resident), the ability to communicate and the provision of written consent to participate in the survey. The exclusion criteria included: concurrent systemic diseases in which periodontal probing, leading to transient bacteremia, might have posed a risk to the patient's overall health, failure to provide written consent to participate in the survey and the occurrence of mental disorders which render the completion of a questionnaire impossible. All participants involved were obliged to provide written informed consent and completed the questionnaire, as well as demonstrate cooperation during the clinical oral examinations. Participants who did not ful l the inclusion criteria were excluded from the study.
The study protocol was approved by the Bioethics Committee of Wroclaw Medical University (permission no. KB 420/2015) in accordance with the Declaration of Helsinki. Participation in the study was voluntary and anonymous, and the collected data were treated con dentially. The population was examined over 24 months. Data on the total number of residents aged 65 and more were derived from Statistics Poland. [10] The sample size was calculated based on the data concerning the number of individuals in this age group who live in the city. With such an assumption, a 95% level of con dence and ± 5% margin of error, a minimum sample size consisted of 384 participants. [11] Participants provided demographic and personal information as well as their medical history. The collected data included: date of birth, gender, marital status, level of education, monthly income (based on the national average income per family member in the year of the study), as well as comorbid systemic diseases.
Evaluation of oral health was conducted by two examiners. Each examiner was asked to study the same group of 10 patients. The ndings were then compared with those of the experienced supervisor. The value of inter-examiner kappa coe cient was 0.874 while the intra-examiner kappa coe cient was 0.870.
Oral examination was performed using the arti cial light, a plane dental mirror and a ball-ended probe (WHO CPI probe). Coronal and root caries was evaluated according to the World Health Organisation criteria, DMFT values and their components. [12] Periodontal condition was assessed in individuals who had more than 2 natural teeth by measuring bleeding on probing (BoP) of 6 sites, gingival pocket depth (PD), clinical attachment loss (CAL) [12] and tooth mobility according to the Miller index. [13] Dental prosthetic status was assessed by taking into account the number of functional tooth units of natural and arti cial teeth on implant-supported and xed prostheses (non-functional tooth units), as well as the information on whether the participants wore partial or complete removable dentures. Moreover, oral dryness was examined as per the Challacombe scale (Clinical Oral Dryness Score, CODS) (12). The level of dryness was categorised based on the number of symptoms observed as mild (1-3), moderate (4-6), or severe. [14,15] The impact of OHRQoL was measured using the previously validated Polish version of the OHIP-14. [16] The questionnaire consisted of 14 questions related to problems that occurred with: 1) trouble with pronouncing words, 2) worsened taste, 3) pain, 4) discomfort while eating, 5) self-consciousness, 6) emotional tension, 7) unsatisfactory diet, 8) interrupted meals, 9) di culty with relaxing, 10) embarrassments, 11) irritability, 12) inability to complete everyday tasks, 13) reduced satisfaction with life, 14) complete inability to function. The questions corresponded to 7 dimensions: functional limitation, pain, psychological discomfort, physical disability, psychological disability, social disability and handicap. Frequency of occurrence was assessed using the ve-point Likert scale: 0 -never, 1 -rarely, 2 -occasionally, 3 -frequently, and 4 -very often. All values were summed up to calculate the total OHIP-14 score which could vary between 0 and 56; the higher the OHIP-14, the poorer the OHRQoL.
Compatibility of the obtained results with a normal distribution was veri ed using the Kolmogorov-Smirnov test. Continuous quantitative variables, distributed in a way not signi cantly different from the norm, were presented as a mean and standard deviation, while the qualitative variables were shown as numbers and percentages.Bivariate and multivariate logistic regression analyses of dependent variables (oral health parameters) and independent variables (OHIP-14 score) were also conducted. Correlation of the independent variables (OHIP) was tested via multiple linear regression analysis using the forward stepwise method. For the independent variables, standardised coe cients and regression coe cients beta with a 95% CI were calculated. The results of all tests were rendered signi cant at the P-value of < 0.05.All analyses were computed using Statistica 13 software (PL StatSoft).

Results
Out of 500 participants in the study, 64.0% were females and 36.0% were males, with the mean age of 74.4 ± 7.4. The majority of participants reported to have secondary education (51.0%), live with family members (62.0%), stay at home without any help (90.8%), and belong to the middle economic class (45.2%). Most of the participants (35.4%) suffered from at least three comorbid systemic diseases (Table 1).

CAL -clinical attachment loss
The total OHIP-14 score amounted to 8.01 ± 13.59 and did not reveal any gender-related differences (7.20 ± 12.90 in men and 8.50 ± 14.00 in women, p = 0.28). Among the OHIP-14 items, "discomfort while eating" had the highest value (0.90 ± 1.43) while "inability to complete everyday tasks" and "complete inability to function" had the lowest value (0.31 ± 0.91 and 0.31 ± 0.92, respectively). The results of the reliability analysis concerning the OHIP-14 items in the study group of 500 elderly citizens indicate very good psychometric properties (Cronbach's alpha = 0.964). In terms of domains, the participants most frequently reported physical pain (1.69 ± 2.51) and psychological discomfort (1.46 ± 2.53). (Table 3)   The present study ndings indicated that all domains of OHIP-14 were positively correlated with DMFT and the number of extracted teeth. A study conducted in Spain in the same age group showed a slightly higher OHIP-14 value and it revealed a correlation with the number of missing teeth [17]. Similarly, in residents of Saudi Arabia aged over 60, the OHIP-14 value was similarly correlated with DMFT. [18] In the UK population in the same age group, OHIP-14 values were found to be signi cantly lower [19], contrary to Iranian residents and a group of the Swedish elderly, where OHIP-14 values were found to be signi cantly higher than in the present study. [20] Inukai et al. also reported a signi cantly higher mean total OHIP-14 scores. It was found that higher chewing ability was correlated with lower OHIP-14 summary scores, which indicated better OHRQoL. The correlation between perceived chewing ability and OHRQoL was not substantially affected by age and number of teeth, but by gender, schooling years, treatment demand and denture status. [21]. Koistinen et al. also found that the factors associated with poor OHRQoL included female sex, oral problems and perception of poor physical, psychological and oral health. Women were more likely to report poor OHRQoL than men. [22] In the present study, however, the OHIP-14 value showed no differences related to the participants' gender The analysis of the present study results using linear regression showed that the number of missing teeth allowed to predict values in all domains of the OHIP-14 scale. Unfortunately, although there are advances in conservative dental treatment, the loss of many natural teeth still occurs in the elderly. It should be emphasised that tooth loss is not an inevitable result of the normal ageing process, but a consequence of untreated or ineffectively treated caries, periodontal disease, traumatic injury, and thus it is a negative indicator of both the patient's health-seeking behaviour and the effectiveness of dental care. According to Jain et al.'s study conducted among the residents of two major cities in India, both age and tooth loss were correlated, however, they had different effects on the OHRQoL. Tooth loss, which was correlated with the increase in age, was associated with a negative impact on the perception of the QoL, whereas the increase in age of the participants had less impact on the perception of QoL. [23] As much as 32.8% of xerostomia cases were reported among the Polish elderly participants. Xerostomia correlated with functional limitation and psychological disability. Paredes-Rodríguez et al. also observed a signi cant correlation between a higher level of xerostomia and a poorer QoL. [24] According to their study results, however, QoL was not related to the number of remaining teeth nor the number of ingested drugs.
The maintenance and reconstruction of tooth structure are of great importance in terms of maintaining proper chewing function. The loss of natural teeth prevents the proper functioning of the masticatory organ and it necessitates the use of prosthetic restorations. In the present study, the use of removable dentures increased functional limitation, physical disability, social disability, and handicap. Parea et al.
focused on the overall satisfaction of edentulous patients treated with conventional dentures. The obtained data enabled the conclusion that the use of conventional complete dentures adversely affected OHRQoL of elderly patients, mainly in the case of lower dentures that required repair and replacement, with removable complete dentures as antagonists. [25] The implementation of the term OHRQoL created new perspectives for the estimation of the extent to which oral health or oral diseases affect a patient's life in general. It changed the perception of the problem from a dental-oriented perspective to a biopsychosocial-dental, thus patient-centred, approach. In the study by Brennan at el., [15] both the objective (income) and the subjective socioeconomic status were associated with OHIP scores. Mean OHIP scores were higher for those born overseas and speaking a language other than English, as well as for smokers and those brushing their teeth less frequently. In the present study, the socioeconomic status did not affect the OHIP score. Living alone resulted in higher functional limitation, psychological discomfort, physical disability and social disability.
McGrath et al. found that the elderly perceived oral health as a signi cant QoL factor in a variety of ways.
The majority of them (73%) considered it important for physical, social and psychological QoL. It was most frequently perceived as the impact affecting eating function and comfort. [26] It should be emphasised that both general and oral health were strongly associated with the elderly, while the general health of seniors with more severe health problems had a signi cant effect on their oral healthparticipants with worse health status suffered more oral health problems. [3] According to the present study, the experience of pain exacerbates when there is an increase in the number of comorbidities and taken medications.
Changes in the oral cavity, which accompany the ageing process, affect all the oral cavity structures. Although overall health status deteriorates with age, there are many ways to manage it so that a person can continue to lead an independent life. Hence, active ageing is about ageing in good health, active participation in society, ful lment in professional life, and independence in daily life. The assessment of OHRQoL has multiple important clinical implications. It represents a multidimensional construct that includes the patient's subjective assessment of their own health, functional and emotional well-being, treatment-related expectations and satisfaction as well as general well-being.
Several limitations have to be taken into consideration in a discussion concerning the results of this study. Firstly, this study was conducted using a self-reported questionnaire to report data such as OHIP-14 which could lead to identi cation bias. However, it was proved by some studies that the questionnaire can be used as a valid and reliable method. Secondly, the use of survey data did not allow us to explain temporal relationships nor to show inferences on causality. Thirdly, when analysing the obtained results, it is essential to bear in mind a possible self-selection error of the study participants -those who joined the study were concerned about their dental problems or they were aware of those problems and were looking for help. Moreover, some persons may have refused to participate in the study due to dental fear. Another interfering factor was related to the use of exclusion criteria. The study protocol was approved by the Bioethics Committee of Wroclaw Medical University (permission no. KB 420/2015) in accordance with the Declaration of Helsinki.

Consent to participate
All participants involved were obliged to provide written informed consent. Participants who did not ful l the inclusion criteria were excluded from the study.

Consent for publication
Not applicable Availability of data material The datasets used and analysed during the current study is available from the corresponding author on reasonable request.