The present cross-sectional study was carried out between September 2016 to January 2017 among individuals aged 60 years and older who attended the outpatient Department of Periodontics, SRM Dental College, Ramapuram, Chennai, Tamil Nadu, India. A total of 230 male and female subjects were recruited. Prior to the beginning of the research, informed consent was obtained from the subjects and the data collection method was approved by the Ethical Committee of SRM University (SRMDC/IRB/2015).

The inclusion criteria were patients aged 60 and above. Patients with known history of psychiatric disorders, severe abnormality in speech and hearing and cognitive impairment were excluded since these will affect the true assessment of depression. The Type 1 error probability (α) was set at 0.1 level. For these assumptions, the minimum sample size was 207. We anticipated a 10% drop out and therefore the projected sample size was set at 230.

The subjects were invited to fill a questionnaire during their regular dental check-up [Table/Fig-1]. The data regarding number of teeth, caries experience (DMFT) and oral hygiene status was then recorded by clinical examination. All investigations were carried out by two trained calibrated examiners. Mean kappa index for inter examiner agreement=0.90.

To assess the severity of depression Yesavage’s GDS shorter version, a 15 question instrument consisting of questions related to how the subject feels over the past 1 week was used to assess depression. A score of 0 to 4 is considered as absence of depression, score of 5 to 9 suggests the presence of mild depression. The score of 10 or above suggests severe depression [15].

Geriatric Depression Scale-short form (GDS-15) is a brief 15-item instrument validated as a screening tool for depression based on self-reported feelings over the past 1-week [16]. “Yes” response to negatively worded questions and “No” response to positively worded questions are given a score of one. The scale has been utilised in the clinical as well as research setting [11]. A validated Tamil GDS short form was used for the study [12].

The subjective oral health instrument used for this present study was the OHIP-14. A validated Tamil OHIP 14 scale was used in the present study [27]. It aims to assess seven dimensions of impacts of oral conditions on people’s OHRQoL including functional limitation, physical pain, psychological discomfort, physical disability, psychological disability, social disability and handicap over a period of one year. The questions were regarding whether you have trouble in pronouncing words, if sense of taste has worsened, painful aching in the mouth and discomfort while eating food. Tensed or have problems with teeth/ gums or denture. Any limit in the kind or amount of food, tensed or find life less satisfying because of problems with your teeth/ gums or denture. The functional and psychosocial impact of problems with teeth, dentures and mouth are assessed by each item and scored as never, hardly ever, occasionally, often and very often. This is assessed for a period of one year [28,29].

The response to each question in the OHIP questionnaire is given a number ranging from 0 to 4. This was done according to the scoring criteria for the OHIP index as given by Slade GD [18]. The response to each question is then totalled and the scores are added for all the 14 questions that are denoted as the cumulative OHIP score or OHIP-ADD score which is maximum of 56.

Characteristics of the study participants are presented as 95% Confidence Intervals (CI), or means and Standard Deviation (SD). To compare the mean values between GDS score groups one-way ANOVA was applied followed by Tukey’s HSD post-hoc tests for multiple pairwise comparisons. To compare proportions between GDS score groups Chi-Square test was applied, if any expected cell frequency was <5 then Fisher’s-exact test was used. Univariate and multivariate logistic regression analysis was done to estimate the Odds ratios of the factors associated with Geriatric depression based on that the confounding variables were eliminated. The relationship between GDS-SF scores and OHIP-14 scores was estimated after adjusting for socio-demographic characteristics and health related behaviours. SPSS version 22.0 was used to analyse the data. Significance level was fixed as 5% (α=0.05).

Socio-demographic and clinical characteristics of the 230 subjects are presented in [Table/Fig-2], women comprised 44.3% of participants (N=102). Approximately, 35.2% of participants were employed at the time of the study. A total of 25.2% of participants were smokers and 31.7% were illiterate. Regarding family circumstances, 32.2% were living without a spouse and 49.6% were living in an old age home. 10.4% (24) were both diabetic and hypertensive and 2.2% (5) were completely edentulous.

In the present study, the prevalence of depression according to GDS was 56.5% (130), of which 47.4% (109) were suffering from mild depression (GDS 5-9) [Table/Fig-3]. The socio-demographic characteristics when correlated with severity of depression, it was observed that there was a strong correlation between habits, marital status and family circumstances (p<0.001). Presence of chronic diseases and education status was also significant to the severity of depression (p=0.002 and p=0.024). The oral hygiene status, overall caries experience (DMFT) and the willingness for dental treatment were also highly significant to the severity of depression (p<0.001) [Table/Fig-4].

In the present study, the correlation between oral health quality of life and severity of geriatric depression score are presented in [Table/Fig-5]. The mean OHIP-ADD score was highest in subjects with severe depression (GDS 10-15) and least in subjects without depression (GDS<5). The OHIP-ADD score strongly correlated with the severity of depression (p<0.001). The individual OHIP items involving functional limitations and physical pain was highly significant to the severity of depression exhibiting higher scores for these domains (p<0.001). Subjects with severe depression experienced greater psychological discomfort (4.41±2.61) and psychological disability (4.09±2.6). Physical disability was more in subjects with severe depression (4.9±2.3). Social disability and social handicap scores were higher in subjects with severe depression. All the 7 domains of the OHIP were highly significant to the severity of geriatric depression suggesting that the subjects with geriatric depression have an overall poor OHRQoL.

The final multinomial regression model for the overall sample to identify socio-demographic and oral hygiene related variables associated with geriatric depression (GDS≥5) was depicted. The factors that were likely to be associated with depression were correlated by the odds ratio [Table/Fig-6]. The Individuals living alone were more likely to be depressed with an odds ratio of 12.4 (95% CI; 3.9-60.6; p=0.001). Individuals with poor oral hygiene had odds ratio of 1.8 (95% CI; 1.79-184.7; p=0.014) and subjects who were not willing for dental treatment was not significantly associated with GDS scores >5, odds ratio of 1.12 (95% CI; 0.49-2.53; p=0.787) respectively.

The present study investigated the relationship between geriatric depression and OHRQoL in an urban geriatric population residing in Chennai, India. The results demonstrated that the prevalence of depression in the present study population to be 56.5% with 9.1% suffering from severe depression which could be attributed to the varied socio-demographic characteristics of subjects like living conditions, employment and presence of chronic diseases. These factors have been previously reported to be associated with depression [8,30].

The severity of geriatric depression was significantly associated with systemic diseases, education status and marital status. Family circumstances had highest impact on depression as observed by the logistic regression analysis with odds ratio of 12.4 (3.9-60.6; p=0.001). This finding was similar to studies in older adult rural population in India where mild depression was associated with education status and living circumstances in elderly [9,13,31]. The oral health status was significantly associated with severity of depression with 78.1% of subjects with depression found to have poor oral hygiene and similarly 73% of subjects with depression were not willing for dental treatment and reported a high DMFT score (decay, missing, filled treatment) suggesting that depression reduces the motivation to maintain a good oral hygiene and attend regular dental care. This is in accordance with Lee GR, who also found a similar trend with DMFT and OHRQoL [32].

Once the elders become isolated from family their utilisation for dental service becomes sparse and moreover, the presence of depression hinders their interest towards improving oral hygiene and a negative self-perception of oral health [33].

The severity of depression was significantly associated with overall OHIP scores suggesting that severity of depression negatively affects the overall OHRQoL. In a Korean community dwelling elderly people, it was observed that oral health impact profile was significantly associated with depression [34]. Similarly, Polat U et al., investigated the relationship among health related quality of life and depression in elderly patients and observed that psychological, physiological and social factors affects the overall quality of life in elders [35].

When the seven dimensions of OHIP were compared to geriatric depression, all were highly associated with depression levels. Subjects with depression had a higher self-preserved functional limitation. This could be due to that most subjects were above 70 years and were removable denture wearers. Similarly, Andrade F et al., found subjects with depression having poor Geriatric Oral Health Assessment index (GOHAI) scores as represented by denture status and number of teeth, resulting in functional limitation [20]. Locker D and Slade G, and Steele JG et al., observed that tooth loss does significantly affect OHIP in older adults [36,37] and more remaining teeth indicated a less-negative impact on quality of life [38]. Likewise, Hassel AJ et al., observed that subjects from 61-98 years and wearing removable dentures had a negative OHIP score and reported a highest impairment of functional limitation [39].

The mean OHIP score in the present study for physical disability was perceived to be higher in subjects with depression which was statistically significant (p<0.001). This could be attributed to the fact that depression might lead to a decline in physical skills required to maintain functional independence and accelerate functional impairment in elderly individuals. This finding is similar to study by Wada T et al., across three Asian countries who observed that there is a significant inverse co-relation between geriatric depression and activities of daily living [40]. The subjects with severe depression had higher physical pain scores which were statistically significant. Physical pain and depression are related as cause and effect; the neurotransmitters that influence both pain and mood are serotonin and norepinephrine [41].

Dementia and subsequent cognitive impairment lead to increased psychological disability as experienced with pain and oral diseases. This finding is similar to Lee KH et al., who observed cognitive function and OHRQoL in older adults and concluded that subjects with poorer cognitive status has significantly worse OHRQoL compared to subjects without cognitive impairment [34]. In the present study, depression was significantly associated with increased social disability and handicap (p<0.001). A study done by Park B et al., found that depression is strongly associated with decreased social skills and impairment of carrying out activities of daily living [42].

This study is novel since it is the first of its kind to assess the relationship between geriatric depression and all dimensions of the oral health impact profile in this population. Additionally, this study is unique since the socio-demographic data and willingness for dental treatment was also assessed.

Considering some study subjects being above 80 years could have experienced mild cognitive impairment that influences the results of the study. Larger population-based longitudinal studies on the association between GDS and OHIP-14 are required in future to extend our results.

The results of the present study suggest there was a strong correlation between GDS and OHIP-14. Presence of depression negatively affects the overall oral health related quality of life. The socio-demographic factors, oral hygiene and dental treatment needs were also associated with severity of depression.