Dose-Response Meta-Analysis on Tooth Loss With the Risk of Cognitive Impairment and Dementia

doi:10.1016/j.jamda.2021.05.009

Journal of the American Medical Directors Association

Volume 22, Issue 10, October 2021, Pages 2039-2045

https://doi.org/10.1016/j.jamda.2021.05.009 Get rights and content

Abstract

Objectives

To quantify the dose-response associations between tooth loss and risk of cognitive impairment and dementia.

Design

Longitudinal studies that examined the association between tooth loss and cognitive function were systematically searched on 6 databases through March 1, 2020. The study adhered to Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) reporting guidelines. Risk estimates were pooled using random-effects models. The dose-response associations were assessed using generalized least squares spline models.

Setting and Participants

Adults from community, institution, outpatient or in-hospital were included in the meta-analysis.

Measures

Cognitive impairment and dementia were defined by neuropsychological tests, diagnostic criteria, or medical records. Tooth loss was self-reported or assessed by clinical examinations.

Results

Fourteen studies were entered into the meta-analysis, including 34,074 participants and 4689 cases with diminished cognitive function. Participants with more tooth loss had a 1.48 times higher risk of developing cognitive impairment [95% confidence interval (CI) 1.18–1.87] and 1.28 times higher risk of being diagnosed with dementia (95% CI 1.09–1.49); however, the association was nonsignificant for participants using dentures (relative risk = 1.10, 95% CI 0.90–1.11). Eight studies were included in the dose-response analysis, and data supported the use of linear models. Each additional tooth loss was associated with a 0.014 increased relative risk of cognitive impairment and 0.011 elevated relative risks of dementia. Edentulous participants faced a 1.54 times higher risk of cognitive impairment and a 1.40 times higher risk of being diagnosed with dementia.

Conclusions and Implications

Moderate-quality evidence suggested tooth loss was independently associated with cognitive impairment and dementia; risk of diminished cognitive function increased with incremental numbers of teeth lost. Furthermore, timely prosthodontic treatment with dentures may reduce the progression of cognitive decline related to tooth loss.

Section snippets

Protocol and Registration

This meta-analysis protocol was registered in the National Institute for Health Research, International Prospective Register of Systematic Reviews (PROSPERO, registration number: CRD42019128023). The reporting of this study was in accordance with Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) Guideline (Supplementary Material 1).²⁰

Search Strategy

We searched 6 databases, including PubMed/MEDLINE, Medline (Ovid), EMBASE (Ovid), CINAHL (EBSCO), Web of Science, and Cochrane Library

Literature Search

Fourteen studies were identified in this review. The study selection process and the literature search results are depicted in Supplementary Material 3. Among the 14 articles, 3 articles conducted separate analyses on either education level (higher and lower),²⁶ cognitive function (cognitive impairment and dementia),²⁷ or gender (male and female);²⁸ therefore, the final meta-analysis contained 17 datasets. Eight studies were included in the dose-response analysis.27, 28, 29, 30, 31, 32, 33, 34

Assessment of Tooth Loss

Discussion

This meta-analysis revealed the association between tooth loss and risk of cognitive impairment and dementia based on 14 longitudinal studies containing 34,074 participants and 4689 cases with diminished cognitive function. Our results indicated that more tooth loss increased the risk of cognitive impairment by 1.48 times and dementia by 1.28 times, even after controlling for a range of potential confounders. A further dose-response analysis detected linear associations between tooth loss and

Conclusions and Implications

In summary, this study provided further support of tooth loss as a risk factor for cognitive impairment and dementia. Furthermore, this review highlights that maintaining good oral health may help preserve cognitive function. The findings also indicate that timely prosthodontic treatment may slow the progression of cognitive decline. In clinical practice, health professionals can play an important role in educating patients and family members on the importance of improving oral health.

Author Contributions

Xiang Qi had full access to all of the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis. Concept and design: Bei Wu. Acquisition, analysis, and interpretation of data: Xiang Qi and Zheng Zhu. Drafting of the manuscript: Xiang Qi. Critical revision of the manuscript for important intellectual content: Brenda L. Plassman, Bei Wu. Statistical analysis: Xiang Qi. Obtained funding: Bei Wu. Supervision: Bei Wu.

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An increasing number of systematic reviews and meta-analyses have been published on the association between oral health and cognitive dysfunction, also known as oral-cognitive links. However, there is great diversity in the oral and cognitive factors included in these studies, with different opinions for clinical practice drawn from the evidence. To understand which oral and cognitive factors are involved in those associations, we conducted an umbrella review of 28 systematic reviews, including 12 meta-analyses, on oral-cognitive links. We found that (a) periodontal diseases, oral microbiome, and dementia were frequently studied, while other factors, such as mastication and mild cognitive impairment, were less commonly investigated, and (b) severe deterioration of oral health, such as severe periodontitis or extensive tooth loss, rather than the presence of oral diseases alone, was strongly associated with cognitive dysfunction. In conclusion, the diversity of oral and cognitive factors included in the review studies reflects the complexity of oral-cognitive links. Clarifying the factors helps to form evidence-based clinical advice for healthcare.
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Periodontal diseases [adjusted hazard ratio (aHR) 1.07, 95% CI 1.04-1.09], dental caries (aHR 1.03, 95% CI 1.00-1.05), and 8-14 missing teeth (aHR 1.07, 95% CI 1.02-1.12) were associated with an increased risk of all-cause dementia. In contrast, either professional dental cleaning or frequent tooth brushing were associated with decreased risks of all-cause dementia (aHR 0.91, 95% CI 0.89-0.93 each; aHR 0.83, 95% CI 0.80-0.86 for both). The increased risks by dental diseases were reduced by oral hygiene care: periodontal diseases with professional dental cleaning (aHR 0.94, 95% CI 0.91-0.98) or tooth brushing ≥2 times/day (aHR 0.97, 95% CI 0.94-1.00) and 1 to 7 missing teeth with professional dental cleaning (aHR 0.94, 95% CI 0.89-0.98) or tooth brushing ≥2 times/day (aHR 0.92, 95% CI 0.89-0.95). Consistent results were noted for AD and VaD and in various subgroup analyses.
Periodontal disease, dental caries, and a high number of missing teeth were independently associated with a higher risk of dementia. Conversely, improved oral hygiene care, such as professional dental cleaning and frequent tooth brushing, may modify the risk of dementia associated with dental diseases.
A Survey of Oral Assessment and Healthcare Education at Nursing Schools in Japan
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Citation Excerpt :
In addition, this study showed that the percentages of the educators who teach about the preventive effects of oral health care on dental diseases, the association of periodontal with systemic diseases, and the use of fluoride for caries prevention were lower than the percentage of those who teach the preventive effect on aspiration pneumonia. Periodontal disease and dental caries are the main causes of tooth loss27 and contribute to oral hypofunction28 and frailty,29 dementia,30 and pneumonia mortality.31 Moreover, periodontal disease is associated with systemic diseases such as cardiovascular disease32 and diabetes.33
This study aimed to investigate the performance of oral assessment and health care education at nursing schools across Japan to identify problems and the need for oral health professional support.
The participants were the academic staff in charge of oral health care education in the basic, adult, gerontological, and home nursing fields of 295 schools in Japan that offered a bachelor's degree in nursing. A questionnaire was sent to 1180 heads of the nursing fields of these schools. They were requested to have oral health care educators complete the survey; data on the performance of oral assessment and health care education and human resources allocated were collected through a questionnaire.
A total of 311 (26%) questionnaires were returned, 196 (63%) of which were completed by oral health care educators. Regarding the performance of oral assessment education, the majority (71%) of them spent less than 2 hours in teaching, and only 24.5% taught the usage of oral assessment tools. Regarding the performance of oral health care education, more than 90% spent less than 2 hours in lecture-based and practical oral health care education, respectively. Less than half taught the association of periodontal diseases with diabetes and cardiovascular diseases and use of fluoride for caries prevention in the lectures, and only approximately 30% taught the usage of an interspace brush or dental floss. Moreover, less than 10% of oral health professionals taught oral health care in lectures or practical oral health care.
This study revealed problems associated with oral assessment and health care education in Japanese nursing schools. To address these, support from oral health care professionals is required. Further studies are also required to reveal problems in oral assessment and health care education in other nursing schools that do not offer a bachelor's degree programme in Japan and other countries.
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The lack of treatment options for congenital (0.1%) and partial (10%) tooth anomalies highlights the need to develop innovative strategies. Over two decades of dedicated research have led to breakthroughs in the treatment of congenital and acquired tooth loss. We revealed that by inactivating USAG-1, congenital tooth agenesis can be successfully ameliorated during early tooth development and that the inactivation promotes late-stage tooth morphogenesis in double knockout mice. Furthermore, Anti- USAG-1 antibody treatment in mice is effective in tooth regeneration and can be a breakthrough in treating tooth anomalies in humans. With approximately 0.1% of the population suffering from congenital tooth agenesis and 10% of children worldwide suffering from partial tooth loss, early diagnosis will improve outcomes and the quality of life of patients. Understanding the role of pathogenic USAG-1 variants, their interacting gene partners, and their protein functions will help develop critical biomarkers. Advances in next-generation sequencing, mass spectrometry, and imaging technologies will assist in developing companion and predictive biomarkers to help identify patients who will benefit from tooth regeneration.
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Estudio transversal con 1826 participantes ≥60 años de la Encuesta Nacional de Salud de Chile, 2016-2017. La salud oral fue evaluada por el número de dientes, la presencia de caries, el uso de prótesis dental y el autorreporte de salud oral y dolor en la cavidad oral. La sospecha de deterioro cognitivo fue evaluada mediante el Mini-Mental State Examination (MMSE). Se empleó regresión logística y lineal, ajustada por variables sociodemográficas y de estilos de vida.
En comparación con personas sin sospecha de deterioro cognitivo, aquellas con sospecha de deterioro cognitivo presentaron cinco dientes menos (13,4 vs. 8,5 dientes), diferencia muy superior en mujeres que en hombres, y mayor frecuencia de dolor oral. El edentulismo y el menor número de dientes se asociaron a mayor probabilidad de sospecha de deterioro cognitivo, asociaciones que no se mantuvieron en modelos ajustados. El dolor oral se asoció a mayor probabilidad de sospecha de deterioro cognitivo (odds ratio: 1,99; intervalo de confianza del 95% [IC95%]: 1,09-3,63). Por cada diente adicional se observó un aumento del 2% (IC95%: 0,01-0,05) en la puntuación del MMSE.
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View all citing articles on Scopus

: XQ and ZZ contributed equally to this study and shared first authorship.

: This study is partially supported by the National Institutes of Health (1R56AG067619 and U01DE027512).

: The authors declare no conflicts of interest.

View full text

Review ArticleDose-Response Meta-Analysis on Tooth Loss With the Risk of Cognitive Impairment and Dementia

Abstract

Objectives

Design

Setting and Participants

Measures

Results

Conclusions and Implications

Section snippets

Protocol and Registration

Search Strategy

Literature Search

Assessment of Tooth Loss

Discussion

Conclusions and Implications

Author Contributions

Alzheimers Dement

Alzheimers Dement

J Am Med Dir Assoc

Front Aging Neurosci

Neurobiol Aging

Eur Psychiatry

J Am Dent Assoc

J Dent

Neurosci Lett

Arch Oral Biol

J Clin Epidemiol

Estimating the global mortality from Alzheimer’s disease and other dementias: A new method and results from the Global Burden of Disease study 2019: Epidemiology/prevalence, incidence, and outcomes of MCI and dementia

Alzheimers Dement

Mild cognitive impairment as a clinical entity and treatment target

Arch Neurol

Mild cognitive impairment: Conceptual, assessment, ethical, and social issues

Clin Interv Aging

Burden of oral disease among older adults and implications for public health priorities

Am J Public Health

Oral hygiene and oral health in older people with dementia: A comprehensive review with focus on oral soft tissues

Clin Oral Investig

Tooth loss increases the risk of diminished cognitive function: A systematic review and meta-analysis

JDR Clin Transl Res

Evidence summary: The relationship between oral health and dementia

Br Dent J

Tooth loss as a risk factor for dementia: Systematic review and meta-analysis of 21 observational studies

BMC Psychiatry

Association between residual teeth number in later life and incidence of dementia: A systematic review and meta-analysis

BMC Geriatr

Association between tooth loss and dementia among older people: A meta-analysis: Association between tooth loss and dementia among older people

Int J Geriatr Psychiatry

Periodontal disease, tooth loss and dementia: Is there a link? A systematic review

Gerodontology

Association between oral health and cognitive status: A systematic review

J Am Geriatr Soc

Influence of lack of posterior occlusal support on cognitive decline among 80-year-old Japanese people in a 3-year prospective study: Influence of occlusion on cognition

Geriatr Gerontol Int

Association between tooth loss and cognitive impairment in community-dwelling older Japanese adults: A 4-year prospective cohort study from the Ohasama study

BMC Oral Health

Preferred reporting items for systematic reviews and meta-analyses: The PRISMA Statement

PLoS Med

Critical evaluation of the Newcastle-Ottawa Scale for the assessment of the quality of non-randomized studies in meta-analyses

Eur J Epidemiol

GRADE: An emerging consensus on rating quality of evidence and strength of recommendations

BMJ

Review Article
Dose-Response Meta-Analysis on Tooth Loss With the Risk of Cognitive Impairment and Dementia