Does remaining teeth and dental prosthesis associate with social isolation? A six‐year longitudinal study from the Japan Gerontological Evaluation Study (JAGES)

Abstract Objectives Social isolation was associated with increased mortality and numerous adverse health outcomes. However, the longitudinal association between oral health and social isolation has not been studied. In this longitudinal prospective cohort study, the association between the number of remaining teeth and dental prosthesis use with social isolation after 6‐years follow‐up was examined. Methods Functionally independent adults aged 65 years or older, who were not socially isolated in 2010, were followed up until 2016 in the Japan Gerontological Evaluation Study. Data from 26 417 participants were analysed after random forest imputation to address missing data. Logistic regression models were used to calculate the odds ratio (OR) for incident social isolation in 2016 after adjusting for age, sex, educational attainment, income, activities of daily living, living area and having depressive symptoms. Results The mean age of the participants at baseline was 72.3 (SD = 5.0). A total of 1,127 (4.3%) participants were socially isolated at follow‐up. Of these, 338 (3.2%) had ≥20 teeth (with or without using dental prosthesis), 171 (3.9%) had 10–19 teeth and used dental prosthesis, 112 (4.2%) had 10–19 teeth and did not use the dental prosthesis, 338 (5.1%) had 0–9 teeth and used dental prosthesis, and 168 (7.6%) had 0–9 teeth and did not use the dental prosthesis. Fully adjusted logistic regression models showed that the OR of incident social isolation was higher for those with fewer teeth; OR = 1.13 (95%CI = 0.96–1.33) for those with 10–19 teeth and OR = 1.36 (95%CI = 1.17–1.58) for those with 0–9 teeth, compared to those with ≥20 teeth. The OR of incident social isolation was lower for those who used a dental prosthesis [OR = 0.90, 95%CI = 0.80–1.02)] compared to those who did not use a dental prosthesis. The interaction between the number of teeth and dental prosthesis use demonstrated that the latter mitigated the incidence of social isolation for participants with tooth loss. Compared to those with ≥20 teeth (with or without prosthesis use), participants with 0–9 teeth that did not use a dental prosthesis were 79% [OR = 1.79, 95%CI = 1.49–2.19] more likely to be socially isolated, whereas participants with 0–9 teeth that used a dental prosthesis were only 23% [OR = 1.23, 95%CI = 1.05–1.45] more likely to be socially isolated. Conclusion Tooth loss was the main predictor for social isolation at follow‐up, while no dental prostheses use was an additional risk factor. Dental prosthesis use may reduce the risk of social isolation especially in those with severe tooth loss.