Effects of an educational intervention on oral hygiene and self-care among people with mental illness in Japan: a longitudinal study

By mail or by telephone, we asked the directors of psychiatric hospitals in Japan to participate in this study. After the directors agreed to participate by returning the letter of agreement, we sent them the consent forms, which were then distributed to individuals attending psychiatric day care centers. Each participant completed a consent form and returned it to us.

We first conducted a survey of knowledge and self-care related to oral hygiene. Second, all respondents viewed an educational presentation on oral hygiene. Third, after 1 week, the respondents again answered questions on knowledge and self-care related to oral hygiene. Fourth, after 1 month, the respondents answered the same questions. Fifth, after 3 months, the respondents again answered the same questions. Finally, the respondents answered the questions again after 6 months.

The questionnaire comprised a pre-questionnaire and post-questionnaires (Additional file 1). The pre-questionnaire was a survey of basic demographic characteristics and self-care related to oral hygiene. Basic demographic characteristics were assessed with 17 items, including name, sex, age, education, height and weight. For age, the category “60s” includes all respondents aged 60 or older. Twenty self-care items were included, based on questions used by the Japan Dental Association [13]. These questions asked, for example, whether respondents were currently concerned about certain dental or intraoral conditions and how many teeth they had. The post-questionnaire included 15 items that were on the pre-questionnaire, as well as six new questionnaire items, such as “did you understand the instruction booklet?” and “how many times did you read the instruction booklet at home?”

We developed the educational program used in this study. It consisted of five units: (1) cause of tooth loss, (2) dental caries, (3) dental cleaning, (4) periodontal disease, and (5) routine dental checkups. The type of information provided was, for example, “Tooth loss is caused by cavities and periodontal disease in 90% of cases, so you need to prevent them,” “Dental plaque is a cause of cavities and periodontal disease,” and “It is more effective to use an interdental brush or floss along with a toothbrush.”

The educational program consisted of a slide show of 37 slides with narration and required 30 min to complete. The researcher delivered the presentation using this program. In addition, we created a booklet containing printouts of the slide show and accompanying narration. Photos of patients’ mouths found in the educational material were used with the permission by oral health association of Niigata prefecture in Japan.

All analyses were performed using the Statistical Package for the Social Sciences (SPSS), Version 23.0. Cross-tabulation and the χ² test were used to compare oral health among patients with different demographic characteristics, physical conditions, and snacking habits. Cross-tabulation and the χ² test were also used to compare patients with different demographic characteristics in terms of snacking, smoking, and self-care. Dunnett’s test was applied to assess changes in self-care items across time points (baseline, after 1 week, after 1 month, after 3 months, and after 6 months). Statistical significance was defined as p <0.05 (α-level = 5%).

This study was approved by the Medical Ethics Committee of Tohoku University Graduate School of Medicine and 19 of the participating psychiatric hospitals. Each participant completed a consent form and returned it to us.

We contacted 25 psychiatric day care centers to request their participation in the study. Of these, we received letters of agreement from 19 of the directors. In total, 390 patients with mental illness completed consent forms. For the baseline questionnaire, there were 323 valid responses. For the questionnaires administered 1 week, 1 month, 3 months, and 6 months after the educational program, there were 218, 226, 191, and 183 valid responses, respectively. There were 142 valid responses including all four time points. Drop-outs were patients who stopped the use of the psychiatric day care centers. Demographic characteristics of the participants are shown in Table 1.

An analysis of 323 valid pre-questionnaire responses was conducted. Participants were asked to select “yes” or “no” for several intraoral conditions: swollen and flabby gums; number of teeth ≤ 19 or ≥ 20; pain; bad breath; and concern about speech, appearance, and occlusion.

The results of the univariate analyses for clarifying these characteristics are shown in Table 2.

When the yes/no groups were compared based on the number of teeth, the significant factors (cross-tabulation, χ² test; p < 0.05) were total length of hospitalization, side effects of drugs, daily consumption of sweets, and smoking.

On the pre-questionnaire, respondents were asked to select “yes” or “no” to indicate whether they smoked and whether their daily consumption of snacks included the following: sweets, fruits, ice cream, cola, and coffee with sugar. The results of the univariate analyses for clarifying these characteristics are shown in Table 3.

When the groups with and without daily consumption of fruits were compared, the significant factors (cross-tabulation, χ² test; p < 0.05) were gender and dry mouth. When the groups with and without smoking were compared, the significant factors (cross-tabulation, χ² test; p < 0.05) were gender, dry mouth, and diabetes.

On the pre-questionnaire, respondents were asked about the following oral self-care practices: tooth brushing after meals, during outings, and before bed; use of fluoride toothpaste; use of interdental brushes or floss; primary care dentist; reasons for dental visits; being too busy to see a dentist sometimes; and having at least one dental checkup per year. Respondents were also asked if they had had dental calculus removed or a teeth cleaning in the last year, if they had received proper brushing instructions at a dental clinic, and if they had family members or other familiar persons who were interested in dental health.

The results of the univariate analyses for clarifying these characteristics are shown in Table 4.

When the groups with and without tooth brushing after meals were compared, the significant factors (cross-tabulation, χ² test; p < 0.05) were gender and duration of mental illness. When the groups with and without tooth brushing before bed were compared, the significant factors (cross-tabulation, χ² test; p < 0.05) were gender, duration of mental illness, and diabetes. When the groups with and without at least one dental checkup per year were compared, gender was the only significant factor (cross-tabulation, χ² test; p < 0.05).

The 142 valid responses for the entire study period were used to investigate the effect of education (Table 5). Dunnett’s test was applied to assess changes in self-care items over the assessed time points (baseline, after 1 week, after 1 month, after 3 months, and after 6 months). Use of fluoride toothpaste was a significant factor from baseline to all time points after the educational program (p < 0.001). Daily use of interdental brushes or floss was significantly different at 6 months after the educational program.

Because of the side effects of drugs, such as hyposalivation and dry mouth, soft drinks containing sugar can easily cause dental caries in patients taking antipsychotic drugs. Smoking, a pernicious habit of many patients with mental illness, is also a factor contributing to the development of periodontal disease [14]. When these risk factors are combined with inadequate oral hygiene, intraoral environments start to deteriorate, potentially causing significant damage in the oral cavity. In this study, the proportion of patients who were men and had had a mental illness for ≥ 10 years was significantly higher among patients who did not brush their teeth before bed, indicating that gender and the duration of disease are factors associated with the lack of self-care. This is consistent with the association between the duration of mental illness and unhealthy teeth reported by Tang et al. in China [15]. Our study also revealed that male patients tended to have unhealthy preferences, such as a lack of daily consumption of fruits, the daily consumption of ice cream or cola, and smoking. In addition, men did not have primary care dentists, and, compared with female patients, a significantly higher proportion of male patients did not undergo routine dental checkups at least once per year. Similarly, Persson et al. reported poor oral hygiene among male outpatients in Sweden [16], suggesting that it is important to establish intervention programs focusing on dental self-care, diet, and regular checkups for male patients with a mental illness. Our results and previous studies have indicated that interventions should target men and those who have had a mental illness lasting many years.

In this study, a significant association was observed between having ≤ 19 teeth and ≥ 5 years of hospitalization. This is consistent with the results of a previous study showing a correlation between the length of stay in a psychiatric ward and the deterioration of intraoral health [4, 8]. In the acute phase of psychiatric illness, physicians have no choice but to admit patients because of the appearance of positive symptoms such as hallucinations and delusions. To manage these symptoms, both physicians and patients focus on the treatment. This phase is also characterized by the inability of patients to maintain sufficient personal hygiene and grooming activities, such as face washing, bathing, tooth brushing, and dressing. These patients therefore require the occasional assistance of health care professionals. However, it is extremely difficult to obtain help with oral hygiene and maintaining good intraoral conditions, especially for those who do not brush their teeth regularly and for patients with psychiatric illness in the acute phase. In a study of psychiatric inpatients in China, Tang et al. reported that 75.3% of these patients had dental caries, 50.4% needed tooth extraction, and 78.8% needed treatment, showing poor intraoral conditions [15]. Furthermore, in Israel, Ramon et al. found that the number of dental caries was higher among psychiatric inpatients (6.7 ± 6.9) than among healthy individuals (1.36 ± 2.0) [9]. Although we did not objectively examine the intraoral conditions of our patients or compare these conditions with those of healthy individuals, the data indicate an association between the healthy life span of teeth and prolonged hospitalization.

The severity of mental health symptoms is not the only factor that prolongs hospitalization. For example, in Japan, approximately 70,000 psychiatric inpatients with stable conditions are regarded as social hospitalization cases, because they have no place to go after leaving the hospital. For that reason, these patients remain in the hospital for an average of 300 days, which is longer than the mean duration of hospitalization in other countries [17]. However, regardless of the reasons for hospitalization, it is essential to maintain the oral health of inpatients. This conclusion is supported by the work of Gurbuz et al., who reported a correlation between the community periodontal index and tooth brushing (beta = 0.59, p = 0.02) among inpatients with schizophrenia in Turkey [18]. After the acute phase of disease characterized by positive symptoms, patients experience negative symptoms such as abulia and autosynnoia, which results in a significant loss of interest in personal hygiene. This is also the case among patients with mood disorders and late-life depression [19]. Patients with mood disorders have, among other things, an increased risk of caries, xerostomia, taste abnormalities, and bruxism [20]. Because of such symptoms specific to mental illness, the maintenance of oral and dental health among psychiatric inpatients has been a challenge across all countries despite the well-known importance of oral hygiene practices.

Our educational program showed the effects of using oral hygiene tools. In a review published in 2016, Khokhar et al. [21] found no evidence from trials that oral health advice results in clinically meaningful outcomes among people with serious mental illness. We think this is because there is doubt about the utility and benefit of oral hygiene education targeted to individuals with mental illness because of uncertainty about the capabilities of these patients and about oral hygiene education itself. As for doubts about the capabilities of patients with mental illness, this attitude should be overcome from the perspective of normalization, and health care researchers need to work diligently to improve the self-care abilities of these patients. For concerns about oral hygiene education in general, the audiovisual learning model in Dale’s Cone of Experience may be effective [22].

In this study, we developed educational materials on oral hygiene for individuals with mental illness and examined the efficacy of these materials using audiovisual aids. Taking into account that individuals with mental illness generally have shorter attention spans and reduced capacity for thinking, we replaced written explanations in the educational materials with cartoons and photographic images as much as possible to reduce the burden to patients and to make the booklet as impactful as possible. Although we used the content of a preexisting instruction booklet on oral hygiene, we also made attempts to attract participants by including problems familiar to individuals with mental illness, such as the relationship between antipsychotic drugs and the oral environment, as well as the relationship between personal preferences, such as soft drinks and smoking, and periodontal disease or dental caries. We hope that the findings of this study will be useful for improving oral hygiene treatment worldwide.