Tooth loss mediates the association between smoking and an increased risk of dementia among older adults: The JAGES prospective cohort study

AIM

Tooth loss has various causes; however, its cause-specific effects on health outcomes remain unclear. This study evaluated whether the association between past/current smoking and risk of dementia was mediated by tooth loss.

MATERIALS AND METHODS

This 9-year-follow-up prospective cohort study targeted adults aged ≥65 years. Dementia incidence during 2013-2019, smoking status (never, past/current) in 2010 and the number of remaining teeth (≤19, ≥20) in 2013 were the outcome, exposure and mediator, respectively. We used causal mediation analysis to fit the Cox proportional hazards model and estimated the hazard ratio (HR) and 95% confidence interval (CI) of the natural indirect effect (NIE) of smoking on dementia incidence through tooth loss and their mediated proportions.

RESULTS

Among 32,986 participants (mean age 72.6 years [1 SD = 5.4]; men 48.4%), the dementia incidence during follow-up was 2.11/100 person-years. Tooth loss significantly mediated the association between past/current smoking and dementia incidence; the NIE of fewer remaining teeth for past/current smokers compared to never smokers was HR = 1.03 (95% CI: 1.02-1.05), and the mediated proportion was 18.0%.

CONCLUSIONS

Tooth loss significantly mediates the association between past/current smoking and an increased risk of dementia among older adults.

Prevalence of dental visits in older Japanese adults receiving public assistance

OBJECTIVES

Exemption from paying dental care costs among recipients of public assistance contributes to universal health care coverage. Although this system might reduce the financial barriers to dental care among patients, there are still several other barriers for public assistance recipients. Therefore, this study examined whether receiving public assistance was associated with a higher prevalence of dental visits for any reason, treatment and prevention.

METHODS

Data were obtained from 16 366 respondents from the 2019 wave of a nationwide cohort study on older adults in Japan. Poisson regression analyses with robust error variance were used to examine the associations between receiving public assistance and dental visits, adjusting for number of teeth, dental pain, periodontal conditions, age, sex, number of family members, education, equivalent household income, working status, instrumental activities of daily living, medical conditions, depressive symptoms, instrumental support and geographical variations.

RESULTS

More than half of the non-recipients of public assistance visited a dentist for some reason in the past 6 months. Meanwhile, only 37% of the recipients visited a dentist. In addition, almost half of the non-recipients had treatment visits, while only 34% of the recipients visited. Furthermore, 46% of the non-recipients had dental visits for prevention, while 32% of the recipients had preventive visits. In the fully adjusted models, compared to non-recipients, public assistance recipients were 24% (Prevalence Ratio [PR]: 0.76, 95% Confidence Intervals [CI]: 0.64, 0.90), 23% (PR: 0.77, 95% CI: 0.65, 0.92) and 21% (PR: 0.79, 95% CI: 0.65, 0.95) less likely to have dental visits for any reason, treatment, and prevention, respectively.

CONCLUSIONS

Although recipients were exempted from dental treatment fees, receiving public assistance was associated with a lower prevalence of dental visits for any reason, treatment and prevention. Future studies should identify the barriers to accessing dental care among public assistance recipients to improve dental visits.

Socioeconomic status and incident depressive symptoms among older adults: A 3-year longitudinal study from the Japan Gerontological Evaluation Study

OBJECTIVES

The association between socioeconomic status (SES) and the onset of depressive symptoms has attracted considerable attention. However, few studies have simultaneously examined the association of multiple SES indicators, including "assets," with the onset of depressive symptoms. Therefore, this study examined the association of four SES indicators in old age ('years of education' 'equivalent income,' 'equivalent assets,' and 'the longest-held job') with new-onset depressive symptoms in a large Japanese dataset.

METHODS

This longitudinal study used panel data of cognitively and physically independent older adults from the Japan Gerontological Evaluation Study (JAGES) conducted in 2013 and 2016. Multivariate logistic regression analysis was conducted to examine the association of each SES indicator with new-onset depressive symptoms, and odds ratios and 95% confidence intervals (CIs) were calculated.

RESULTS

We analyzed the data of 40,257 older adults, with a mean age (± standard deviation) of 72.9 (±5.5) years. In the follow-up survey, 4292 older adults had new-onset depression symptoms (10.7%). 39.3% had 10-12 years of education. 36.9% had an equivalent income of up to JPY 1.99 million. 24.4% had equivalent assets of JPY 4-17.99 million. Most had a clerical job for the long time. Furthermore, fewer years of education (males: OR = 1.42, 95% CI = 1.22-1.64, p-value <0.001/females: 1.26, [1.09-1.47], p = 0.002), lower income (males: 1.64, [1.34-2.01], p < 0.001/females: 1.82, [1.49-2.22], p < 0.001), and fewer assets (males: 1.40, [1.16-1.68], p < 0.001/females: 1.21, [1.02-1.42], p = 0.025) resulted in higher odds of having new-onset depressive symptoms, even when other SES indicators were entered simultaneously.

CONCLUSIONS

All four SES indicators have an independent association with the development of new-onset depressive symptoms among older adults, reflecting different aspects of SES. The association between the "longest-held job" and new-onset depressive symptoms can be largely explained by other SES indicators. A multifaceted and lifetime approach is required to prevent the onset of depressive symptoms in old age.

Lower socio-economic status in adolescence is associated with poor oral health at an older age: Mediation by social and behavioural factors

AIM

To examine the mediators between lower socio-economic status (SES) in adolescence and oral health at an older age to uncover the underlying mechanisms of the association.

METHODS

Participants (n = 21 536) aged ≥65 years from the Japan Gerontological Evaluation Study were evaluated. The dependent variables were self-rated chewing difficulty and having ≤19 remaining teeth. The main independent variable was self-perceived SES in adolescence. The Karlson-Holm-Breen method was used for mediation analysis.

RESULTS

Mean age of the participants was 74.8 years (standard deviation = 6.4), and 51.5% were female. Overall, 5598 (26.0%) participants reported chewing difficulty and 9404 (43.7%) had ≤19 remaining teeth. Lower SES in adolescence was associated with a higher prevalence of chewing difficulty (odds ratio [OR] = 1.38, 95%confidence interval [CI] = 1.29-1.48; total effect). After controlling for mediators, OR for lower SES in adolescence was 1.22 (95%CI = 1.13-1.30; direct effect) and 1.13 (95%CI = 1.11-1.16; indirect effect). Mediators, prominently the number of teeth and income, explained 39.3% of the associations. Lower SES in adolescence increased the odds of ≤19 remaining teeth by OR = 1.23 (95% CI = 1.16-1.31; total effect). After controlling for mediators, the OR for lower SES in adolescence was 1.03 (95%CI = 0.97-1.10; direct effect) and 1.19 (95%CI = 1.16-1.23; indirect effect). Mediators, prominently educational attainment, explained 85.0% of the associations.

CONCLUSIONS

Lower SES in adolescence was associated with poor oral health at an older age through mediators. Approaches that consider social determinants from the beginning of the life course are required.

Social isolation, loneliness, and their correlates in older Japanese adults

BACKGROUND

Loneliness and social isolation are elevated in older adults and associated with a range of detrimental outcomes. Despite this, there has been little research on these phenomena or on similarities and differences in their occurrence or combination in older Japanese adults. The current study aims to (i) determine what factors are associated with social isolation and loneliness among older adults in Japan; and (ii) describe the characteristics of individuals who are socially isolated but not lonely, as well as those who feel lonely but are not socially isolated.

METHODS

Data were analysed from 13 766 adults aged ≥65 years who participated in the 2019 wave of the Japan Gerontological Evaluation Study. Poisson regression analysis was used to examine associations.

RESULTS

Among older Japanese adults, the attributes of higher age, male gender, lower socioeconomic status, being a welfare recipient, and having depressive symptoms were associated with social isolation, while lower socioeconomic status, unemployment, welfare receipt, and poor physical and mental health were associated with loneliness. In addition, better educated, and mentally and physically healthy people were less likely to feel lonely even when socially isolated, while people who were not working and who had mental or physical health problems were more likely to feel lonely even if they were not socially isolated.

DISCUSSION

Our results indicate that in order to reduce unwanted social isolation and loneliness among older Japanese adults, in the first instance the focus should be on those individuals who are socioeconomically disadvantaged and unhealthy.

Association between gut microbiota composition and glycoalbumin level during pregnancy in Japanese women: Pilot study from Chiba Study of Mother and Child Health

AIMS/INTRODUCTION

Gut microbiota have various effects on human health. Some previous reports have shown that gut microbiota change during pregnancy and affect metabolism, but others have shown that microbiota do not change. Here, we examined the gut microbiota and glycoalbumin levels of 45 healthy Japanese women during pregnancy.

MATERIALS AND METHODS

We carried out 16S rRNA gene sequencing analyses of maternal stool samples and compared the gut microbiota composition of samples from women in early and late pregnancy. We also examined the association between gut microbiota and maternal characteristics, including glycoalbumin.

RESULTS

Microbiota composition in early and late pregnancy did not differ, according to principal coordinate analysis of weighted and unweighted UniFrac distances. Shannon indices were not different between early and late pregnancy. The proportion of one phylum, TM7, significantly decreased in late pregnancy compared with early pregnancy, but the proportions of other major phyla did not change. The Shannon index of late pregnancy was negatively associated with pregestational body mass index and positively correlated with glycoalbumin level, with adjustment of covariates.

CONCLUSIONS

We concluded that Japanese women did not show obvious differences in gut microbiota during pregnancy, except for TM7, and that the diversity of gut microbiota might affect maternal metabolism. As this study had limited statistical power, further large-scale studies are required.