Are Lowered Socioeconomic Circumstances Causally Related to Tooth Loss? A Natural Experiment Involving the 2011 Great East Japan Earthquake

Abstract

Oral health status is correlated with socioeconomic status. However, the causal nature of the relationship is not established. Here we describe a natural experiment involving deteriorating socioeconomic circumstances following exposure to the 2011 Great East Japan Earthquake and Tsunami. We investigated the relationship between subjective economic deterioration and housing damage due to the disaster and tooth loss in a cohort of community-dwelling residents (n = 3,039), from whom we obtained information about socioeconomic status and health status in 2010 (i.e., predating the disaster). A follow-up survey was performed in 2013 (postdisaster), and 82.1% of the 4,380 eligible survivors responded. We estimated the impact of subjective economic deterioration and housing damage due to the disaster on tooth loss by fitting an instrumental variable probit model. Subjective economic deterioration and housing damage due to the disaster were significantly associated with 8.1% and 1.7% increases in the probability of tooth loss (probit coefficients were 0.469 (95% confidence interval: 0.065, 0.872) and 0.103 (95% confidence interval: 0.011, 0.196), respectively). In this natural experiment, we confirmed the causal relationship between deteriorating socioeconomic circumstances and tooth loss.

High prevalence of toothache among Great East Japan Earthquake survivors living in temporary housing

“…Similarly, the fundamental psychosocial and oral status of participants, especially residents in temporary housing at predisaster were mostly unknown. Matsuyama et al reported that the survivors’ low socio‐economic condition due to the GEJE increased the tooth loss. Since the entry criteria for relocating to prefabricated temporary housing partially included the income limits on applicants for living expenses, we cannot rule out selection bias due to low health status among low‐income people living in temporary housing.…”

“…Recently, people living in prefabricated housing tended to elderly, economically disadvantaged, and health status of prefabricated housing dwellers was exacerbated over time after the GEJE, possibly due to employment and income issues at postdisaster, which were potential factors associated with toothache . Therefore, socio‐demographic characteristics, lifestyle, and health condition variables were included in the analyses as covariates such as the subjects sex, age, subjective economic status, smoking habits (“Yes” or “No”), and psychological distress using the six‐item Kessler Psychological Distress Scale (K6), and insomnia using the eight‐item Athens Insomnia Scale (AIS‐8) …”

“…Recently, people living in prefabricated housing tended to elderly, economically disadvantaged, and health status of prefabricated housing dwellers was exacerbated over time after the GEJE, possibly due to employment and income issues at postdisaster, 4-6 which were potential factors associated with toothache. 8,16 Therefore, socio-demographic characteristics, lifestyle, and health condition variables were included in the analyses as covariates such as the subjects sex, age, subjective economic status, smoking habits ("Yes" or "No"), and psychological distress using the six-item Kessler Psychological Distress Scale (K6), 27,28 and insomnia using the eight-item Athens Insomnia Scale (AIS-8). 29 The participants were divided into the following five groups In subgroup analysis to determine significant association of subjective toothache prevalence with residence after adjustment for oral health-related mediators, the presence of dental caries, gum bleeding and dental treatment needs from data of individual dental examinations were included in the model.…”

“…The local government defined the entry criteria for relocation to prefabricated temporary housing as any person who has lost a place of residence owing to the GEJE and has difficulty securing new dwelling for long‐term occupation through personal efforts, such as household economy . Accordingly, almost half of the survivors relocated to prefabricated housing after the GEJE and had to adapt to and/or establish a new socio‐economic situation and lifestyle . Thus, residential issues in prefabricated housing can have additive impact on the psychosocial status of disaster survivors .…”

“…6 Accordingly, almost half of the survivors relocated to prefabricated housing after the GEJE and had to adapt to and/or establish a new socio-economic situation and lifestyle. [6][7][8] Thus, residential issues in prefabricated housing can have additive impact on the psychosocial status of disaster survivors. 4,5 However, the impact of residence in prefabricated housing on oral health as compared to other residences is unclear.…”