1 INTRODUCTION

There is evidence that people with a serious mental illness (SMI; ie psychosis, bipolar disorder) experience worse oral health outcomes than the general population.1 For example, past research has indicated that people with SMI are 2.8 to 3.4 times as likely to be edentulous (complete loss of all teeth) and have significantly higher rates of decayed, missing or filled teeth (DMFT) or surfaces (DMFS) in comparison with the general population.2-4 Suboptimal oral health can have a detrimental impact on physical and psychological functioning.5 The oral cavity plays a crucial role in the overall well-being of a person and damage thereof can cause considerable suffering by affecting basic and essential functions like eating and speaking.6 Severe caries (tooth decay) leads to pain, discomfort, disfigurement, acute and chronic infections, and eating and sleeping disruption as well as a higher risk of hospitalisation, high treatment costs and lost workdays.7 Research suggests that there is a link between poor oral health and chronic disease, such as diabetes and cardiovascular diseases.8, 9 The ability to smile can also be affected,5 which can impact on self-esteem10 and the ability to socialise with others. 6

The reasons for poor oral health outcomes in people with SMI are likely complex and may include higher rates of drug misuse,11 smoking12 and medication side effects (eg xerostomia).13 Poor oral health in this population may also be due to reduced levels of oral health self-care behaviours (eg dental care, toothbrushing). Some, but not all, studies have suggested that people with a SMI are less likely to attend routine dental visits and, when they do, are more likely to have teeth extracted rather than filled.2-4 This could explain the high rate of edentulous in this population. An increased focus on preventative practices has improved oral health outcomes in the general population.14 Further research is needed to understand levels of oral health behaviours in people with SMI, which could inform future prevention and intervention strategies, leading to better outcomes. It may help to understand oral health inequalities in people with SMI.

1.1 Aims of the study

The aim of this review was to better understand utilisation of oral health self-care behaviours in people with SMI. It used meta-analytic methods to synthesise the size and consistency of differences in oral health self-care behaviours between people with a SMI and non-clinical comparator samples. It also aimed to narratively review studies without a non-clinical comparator sample to better summarise the existing literature.

2 MATERIAL AND METHODS

This review adhered to the Preferred Reporting Items for Systematic Reviews and Meta-analyses standards with a protocol published on PROSPERO [CRD42020176779].

2.1 Eligibility criteria

The inclusion criteria were as follows: (i) case-control, cohort, cross-sectional, longitudinal and epidemiological design study; (ii) publication in an English language peer-reviewed academic journal; and (iii) a quantitative measure of an oral health self-care behaviour. We defined oral health self-care behaviours as actions that individuals take to improve or preserve good oral health.14 This included owning a toothbrush, dental care attendance and frequency of toothbrushing.

Studies were required to include a sample of at least 75% of people diagnosed with a SMI in accordance with the Diagnostic and Statistical Manual (DSM-III or later) or International Classification of Disease (ICD-9 or ICD-10) criteria. SMI is a contentious, but widely used term often including a range of diagnoses such as personality disorders, major depression disorder and dementia.2, 3 However, for the purpose of this review, SMI was defined as the collective term for people with a diagnosis of a psychotic or a bipolar spectrum disorder to maintain consistency with the UK-based National Institute for Health and Care Excellence (NICE) guidance and the majority of past literature15 Specific diagnostic criteria included schizophrenia, schizophreniform, schizoaffective disorder, delusional disorder, bipolar I and bipolar II. Participants who met the operational criteria for an early intervention service for first episode psychosis were included to allow for diagnostic uncertainty in younger age groups. For the purpose of the meta-analysis, eligible studies were required to include valid comparator group (eg general population sample, non-clinical comparator).

2.2 Screening procedure

Systematic searches were conducted in Medline, EMBASE, PsycINFO and CINAHL to identify peer-reviewed articles published between January 1980 and April 2020. Search terms were entered in blocks relating to serious mental illness (severe mental or serious mental or chronic mental or schizo* or psychoti* or psychos* or hallucinat* or paranoi* or bipolar or mania or manic) and oral health (oral health or oral hygiene or tooth* or teeth* or dent*). The search terms were developed based on the authors’ clinical experience and relevant past reviews.2-4, 16 In cases where papers were unavailable or the data were insufficient to confirm eligibility or generate an effect size, information was requested from the primary or corresponding author. The first author (ET) screened the reference lists of eligible articles, citing articles and relevant reviews.2-4, 16 Ten per cent (805 studies) of titles and abstracts were double rated by another author (TV), with high levels of agreement (k = 0.84). At least two of the authors screened each of the full articles to confirm eligibility with discrepancy resolved through consensus.

2.3 Data extraction

Relevant study information (eg study design, sample size and type of sample) was extracted by the first author (ET). For the meta-analysis, outcome data were independently extracted by two authors (ET and JPC) to calculate an effect size (ICC = 0.95, p > 0.001). If multiple time points were presented (eg dental visit within one year and dental visit within two years), the lower timescale analysis was selected to ensure consistency. When possible, we extracted analyses that controlled for covariates (eg adjusted odds ratios).

2.4 Quality assessment

An adapted version of the Effective Public Health Practice Project (EPHPP) tool17 was used to evaluate the overall quality of the included articles due to its suitability for assessing public health-focused quantitative studies. The EPHPP has demonstrated good construct and content validity and interrater reliability.18 Consistent with previous review papers,19, 20 the tool was adapted to account for the observational design of eligible studies. Domains that were not considered relevant (design; blinding; intervention integrity; withdrawals and drop-outs) to the included studies were omitted. The design domain pertained to randomisation procedures for intervention evaluations and was therefore not relevant to the reviewed literature and excluded.

The adapted version of the EPHPP consisted of four domains: selection bias, confounders, data collection methods and analyses. Each domain was rated as strong, moderate or weak, and from this, a global rating was derived based for each domain. In the original EPHPP, analyses ratings were not used to calculate the global rating. However, consistent with previous adaptations,21 a decision was made to include analyses scores in the overall global rating as appropriateness of analysis was deemed to be integral to the quality of the study. Articles were rated by two authors (ET and TV; 79% agreement), and, in cases of discrepancy, consensus was reached with input from a third author.

2.5 Statistical analysis 2.5.1 Meta-analysis

We used comprehensive meta-analysis (CMA, v3)22 to generate effect sizes and conduct analysis for all outcomes with K > 3. Study effect sizes were transformed into odds ratios and a random effects model was utilised as statistical heterogeneity was expected across studies.23 Heterogeneity was explored through the use of the Q test and I2 statistic and a sensitivity analysis was conducted to assess whether any individual study had greater influence over the overall effect size.

2.5.2 Narrative synthesis

In order to appraise the wider literature in this area, all studies without a comparator group were narratively synthesised using the synthesis without meta-analysis (SWiM)24 guidelines. Outcomes were grouped according to oral health self-care behaviours and the corresponding literature was tabulated using the population, intervention, comparator and study type (PICOS) framework to summarise the literature and explore clinical heterogeneity. A weighted average was calculated for key outcomes, using all available data, even those without a clinical comparator.

3 RESULTS

The PRISMA flowchart (Figure 1) displays the screening process. Thirty-three studies25-57 were eligible for inclusion. The total sample comprised of 446,932 people with a SMI and 6,284,176 controls. Further information was provided by seven authors26, 29, 35, 38, 44, 48, 57 to either confirm eligibility or produce an effect size. Table 1 displays the descriptive information on the included studies.

PRISMA Flow Diagram of article screening

TABLE 1. Descriptive information on included studies Study ID Study design Population Diagnosis Status Country Sample size Comparator Type Outcome Adams 2017 Clustered RCT, baseline data First episode psychosis Outpatient UK

Case: 1248

Control: 17849

Adult Dental Health Survey (ADHS) Dental service use, toothbrush frequency, technique and ownership Agarwal, 2019 RCT, Baseline data Schizophrenia Outpatient India 111 N/A Toothbrushing frequency, technique, maintenance of toothbrush, aid for cleaning tongue and mode for cleaning teeth Corridore, 2017 Cross-sectional Schizophrenia, schizoaffective, borderline personality disorder Therapeutic community Italy 67 N/A Dental service usage and toothbrushing frequency Cunha 2017 Case-control Bipolar disorder Outpatient Brazil

Case: 176

Control: 176

Existing study datasets Dental service use Denis, 2017 Cross-sectional Schizophrenia Inpatient and outpatient France 90 N/A Dental service usage and toothbrushing frequency Denis, 2019 Cross-sectional Schizophrenia Inpatient and outpatient France 109 N/A Dental service usage and toothbrushing frequency Denis 2020 Epidemiological Schizophrenia Inpatient and outpatient France

Case: 2,213

Control: 578,006

General population database Dental service usage (scaling) Dickerson, 2003 Case-control Schizophrenia, schizoaffective disorder Outpatient United States

Case: 100

Control: 2705

National health and nutrition survey Dental service usage Djordevic, 2019 Case-control Schizophrenia Inpatient Serbia

Case: 190

Control: 190

Community sample of patients with localised or generalised chronic periodontitis Toothbrush frequency and technique Eltas, 2013 Cross-sectional Schizophrenia Outpatient Turkey 53 N/A Toothbrush frequency Eskelinen, 2017 Cross-sectional Schizophrenia, schizoaffective disorder, other schizophrenia spectrum disorder Outpatient Finland 275 Dental service use Gandre, 2020 Epidemiological Psychotic and bipolar disorder Outpatient and inpatient France

Case: 413,437

Control: 1,240,311

French national health data system Dental service use Gurbuz, 2011 Cross-sectional Schizophrenia Inpatient Turkey 330 Toothbrushing frequency Hede, 1992 Case-control Schizophrenia, reactive psychosis, manic depression Outpatient Denmark

Case: 84

Control: 2548

General population survey Dental service use and toothbrushing frequency Hsieh, 2011 Pre-test post-test design, baseline data Schizophrenia Inpatient Taiwan 100 N/A Toothbrush frequency and maintenance of toothbrush Janhardanan, 2011 Case-control Schizophrenia Outpatient United States

Case: 198

Control: 113

Community comparison group Dental service usage Jovanovic, 2010 Case-control Schizophrenia, NOS psychosis, schizoaffective disorder, persistent psychotic disorder, bipolar disorder Inpatient Serbia

Case: 186

Control: 186

Community comparison group Dental service use, toothbrush frequency, technique and maintenance of toothbrush Lynch, 2005 Cross-sectional Schizophrenia, other Inpatient Northern Ireland 65 N/A Toothbrush ownership McCreadie, 2004 Case-control Schizophrenia Outpatient Scotland

Case: 93

Control: 28,471

General population survey Dental service usage, toothbrushing frequency, flossing, mouthwash use Nayak, 2020 Cross-sectional Schizophrenia, mania Outpatient India 250 N/A Toothbrush frequency Ngo, 2018 Cross-sectional Schizophrenia, Intellectual Disability, other Inpatient Singapore 191 Toothbrushing frequency Nielson, 2011 Epidemiological Schizophrenia Inpatient and outpatient Denmark

Case: 21,417

Control: 3,790,446

National health insurance database Dental service use Pelletier, 2015 Cross-sectional Schizophrenia, schizotypal disorder, delusional disorder Outpatient Canada 146 Toothbrushing frequency Patrick, 1996 Cross-sectional Schizophrenia Outpatient United States 353 N/A Dental service use Salsberry, 2005 Cross-sectional Schizophrenia, schizophreniform, schizoaffective disorder, delusional disorder, ICD-9 – Paranoid disorders Outpatient United States 230 Dental service use Singh, 2017 Cross-sectional Schizophrenia Outpatient India 71 Dental service use, toothbrushing frequency, mode and material for cleaning teeth Singh, 2019 Cross-sectional Schizophrenia Outpatient India 156 Dental service use, toothbrushing frequency, mode and material for cleaning teeth Stiefel, 1990 Case-control Schizophrenia, bipolar disorder, other non-organic, personality disorder Outpatient United States

Case: 37

Control: 29

Community comparison group Dental service use, toothbrushing frequency and flossing. Tani, 2012 Cross-sectional Schizophrenia, schizoaffective disorder, delusional disorder, acute and transient psychotic disorder Inpatient Japan 523 N/A Toothbrushing frequency Teng, 2016 Epidemiological Schizophrenia, delusional disorders Inpatient and outpatient Taiwan

Case: 4298

Control: 623,175

National insurance research database Dental service use Tredget, 2019 Cross-sectional Schizophrenia Outpatient Wales 106 N/A Dental service usage, toothbrush frequency and mouthwash use Wieland, 2010 Cross-sectional Schizophrenia, schizoaffective disorder, bipolar disorder, schizotypal personality disorder Outpatient Australia 20 Dental service use, toothbrushing frequency, flossing and mouthwash use Xiong, 2010 Cross-sectional Bipolar, psychotic disorder Outpatient United States 170 N/A Dental service usage 3.1 Quality appraisal

Findings from the quality assessment are summarised in Table 2. Six studies obtained strong scores, seven moderate and 20 weak. Limitations predominantly related to data collection as the outcome measures were typically not validated and had poor reliability. Studies tended to have a broader focus than oral health self-care behaviours. Therefore, the analysis in this area tended to be basic (eg percentages) and did not account for confounders, leading to higher rates of weak ratings.

TABLE 2. Quality assessment Study ID Selection Bias Confounders Data collection Analysis Global rating Adams 2017 Moderate Weak Weak Moderate Weak Agarwal, 2019 Moderate Moderate Weak Strong Moderate Corridore, 2017 Weak Weak Weak Moderate Weak Cunha 2017 Moderate Moderate Weak Strong Moderate Denis, 2017 Moderate Strong Weak Strong Moderate Denis, 2019 Weak Strong Weak Strong Weak Denis 2020 Strong Strong Strong Strong Strong Dickerson, 2003 Moderate Strong Moderate Strong Strong Djordevic, 2019 Moderate Moderate Weak Strong Moderate Eltas, 2013 Moderate Weak Weak Moderate Weak Eskelinen, 2017 Moderate Weak Weak Strong Weak Gandre, 2020 Strong Strong Strong Strong Strong Gurbuz, 2011 Moderate Moderate Weak Moderate Moderate Hede, 1992 Moderate Weak Weak Weak Weak Hsieh, 2011 Weak Weak Weak Weak Weak Janhardanan, 2011 Moderate Strong Weak Moderate Moderate Jovanovic, 2010 Moderate Weak Weak Strong Weak Lynch, 2005 Weak Weak Weak Weak Weak McCreadie, 2004 Moderate Weak Weak Weak Weak Nayak, 2020 Weak Weak Weak Moderate Weak Ngo, 2018 Strong Weak Weak Moderate Weak Nielson, 2011 Strong Moderate Strong Strong Strong Patrick, 1996 Weak Weak Weak Moderate Weak Pelletier, 2015 Weak Weak Weak Weak Weak Salsberry, 2005 Strong Strong Strong Moderate Strong