Community social support and onset of dementia in older Japanese individuals: a multilevel analysis using the JAGES cohort data

Association Between Oral Malodor and Dementia: An 11-Year Follow-Up Study in Japan

Background

As infrequent social interaction is a potential risk of dementia, oral malodor may increase the risk of dementia, including Alzheimer's disease.

Objective

This study investigated the association between malodor and dementia.

Methods

We used the Japan Public Health Center-based Prospective Study data obtained at Yokote City. A total of 1,493 individuals aged 56 to 75 years underwent a dental examination and self-reported survey from May 2005 to January 2006. Follow-up for the onset of dementia was conducted using long-term care insurance data from 2006 to 2016. Hazard ratios of oral malodor on dementia were estimated by the Cox proportional hazards model. The inverse probability-weighted Cox model was used as a sensitivity analysis.

Results

The study comprised 1493 participants (53.6% women) with a mean age of 65.6 (SD = 5.8) years old; at the end of the follow-up, 6.4% (n = 96) developed dementia, and the percentage was 20.7 in severe malodor group. Throughout 15274.133 person-years of follow-up, the average incidence rate for the onset of dementia per 1000 person-years was 6.29. The highest incidence rate was seen in participants with severe malodor (22.4 per 1000 person-years). After adjusting for confounders, compared to those with no malodor, there was a 3.8 (95% confidence interval: 1.5 to 9.4) times greater hazard of developing dementia in participants with severe malodor. The inverse probability weighted Cox model confirmed the same trend with an adjusted marginal hazard ratio of 4.4 (1.2 to 16.4).

CONCLUSIONS

A significant association between oral malodor and the onset of dementia exists.

Utilization of Japanese long-term care-related data including Kaigo-DB: An analysis of current trends and future directions

Despite high expectations from the government and researchers regarding data utilization, comprehensive analysis of long-term care (LTC)-related data use has been limited. This study reviewed the use of LTC-related data, including Kaigo-DB, in Japan after 2020. There was an increase in studies using LTC-related data in Japan between 2020 and 2021, followed by a stabilization period. The national government provided 13.5% of this data (6.5% from Kaigo-DB), while prefectures and municipalities contributed 85.2%, and facilities provided 1.3%. The linked data used in 90.4% of the studies primarily consisted of original questionnaire or interview surveys (34.6%) and medical claims (34.0%). None of the studies based on Kaigo-DB utilized linked data. In terms of study design, cohort studies were the most common (84.6%), followed by descriptive (5.1%), cross-sectional (3.2%), and case-control studies (1.3%). Among the 138 individual-based analytical descriptive studies, the most frequently used LTC-related data as an exposure was LTC services (26.8%), and the most common data used as an outcome was LTC certification or care need level (43.5%), followed by the independence degree of daily living for the older adults with dementia (18.1%). To enhance the use of LTC-related data, especially the valuable national Kaigo-DB, insights can be gleaned from how researchers effectively utilize municipal and prefectural data. Streamlining access to Kaigo-DB and enabling its linkage with other datasets are promising for future research in this field.

Functional social support and cognitive function in middle- and older-aged adults: a systematic review of cross-sectional and cohort studies

BACKGROUND

Intact cognitive function is crucial for healthy aging. Functional social support is thought to protect against cognitive decline. We conducted a systematic review to investigate the association between functional social support and cognitive function in middle- and older-aged adults.

METHODS

Articles were obtained from PubMed, PsycINFO, Sociological Abstracts, CINAHL, and Scopus. Eligible articles considered any form of functional social support and cognitive outcome. We narratively synthesized extracted data by following the Synthesis Without Meta-Analysis (SWiM) guidelines and assessed risk of bias using the Newcastle-Ottawa Scale (NOS).

RESULTS

Eighty-five articles with mostly low risk-of-bias were included in the review. In general, functional social support-particularly overall and emotional support-was associated with higher cognitive function in middle- and older-aged adults. However, these associations were not all statistically significant. Substantial heterogeneity existed in the types of exposures and outcomes evaluated in the articles, as well as in the specific tools used to measure exposures and outcomes.

CONCLUSIONS

Our review highlights the role of functional social support in the preservation of healthy cognition in aging populations. This finding underscores the importance of maintaining substantive social connections in middle and later life.

SYSTEMATIC REVIEW REGISTRATION

Rutter EC, Tyas SL, Maxwell CJ, Law J, O'Connell ME, Konnert CA, Oremus M. Association between functional social support and cognitive function in middle-aged and older adults: a protocol for a systematic review. BMJ Open;10(4):e037301. https://doi.org/10.1136/bmjopen-2020-037301.

Association between social integration and risk of dementia: A systematic review and meta-analysis of longitudinal studies

BACKGROUND

Dementia is an emerging public health issue. Growing evidence emerged on the association between social integration and the risk of dementia. However, the magnitude of the association between different aspects of social integration and the risk of dementia is unclear.

METHODS

Five databases were systematically searched. Newcastle-Ottawa scale for assessing the quality of the reporting was used for quality appraisal. Longitudinal cohort studies examining the association between social integration and the risk of dementia were analyzed using random effects model. A series of sensitivity analyses was conducted to enhance the robustness of the findings.

RESULTS

Forty publications generated from 32 studies/databases were included. The meta-analysis showed that strong social engagement (overall RR = 0.81, 95% CI = 0.74-0.89, p < 0.001) and frequent social contact (overall RR = 0.86, 95% CI = 0.76-0.97, p = 0.018) were positively associated with decreased risk of dementia. The influence of social support (overall RR = 0.92, 95% CI = 0.80-1.06, p = 0.238) and close social contact (overall RR = 0.74, 95% CI = 0.48-1.13, p = 0.167) was not significant. Loneliness was significantly associated with an increased risk of dementia (overall RR = 1.42, 95% CI = 1.26-1.60, p < 0.001), whereas the influence of social isolation (overall RR = 1.58, 95% CI = 0.80-3.12, p = 0.192) was not significant. A larger social network size (RR = 0.75, 95% CI = 0.59-0.97, p = 0.028) was a promising influencing factor even though the number of studies was insufficient for a meta-analysis. However, the heterogeneity among studies was generally high even though sensitivity analysis was conducted.

CONCLUSIONS

Our findings reveal that high social engagement and frequent social contact are significantly associated with a lower risk of dementia, whereas loneliness is associated with a higher risk. The promising impact of large social network size is also identified. Substantial heterogeneity appeared in most of the analysis, making the inference tentative. Nevertheless, the sensitivity analysis provided valuable implications that enhancing social engagement and reducing loneliness may prevent or delay the onset of dementia among middle-aged and older adults.

Psychosocial factors and hippocampal subfields: The Medea-7T study

Specific subfields within the hippocampus have shown vulnerability to chronic stress, highlighting the importance of looking regionally within the hippocampus to understand the role of psychosocial factors in the development of neurodegenerative diseases. A systematic review on psychosocial factors and hippocampal subfield volumes was performed and showed inconsistent results, highlighting the need for future studies to explore this relationship. The current study aimed to explore the association of psychosocial factors with hippocampal (subfield) volumes, using high-field 7T MRI. Data were from the Memory Depression and Aging (Medea)-7T study, which included 333 participants without dementia. Hippocampal subfields were automatically segmented from T2-weighted images using ASHS software. Generalized linear models accounting for correlated outcomes were used to assess the association between subfields (i.e., entorhinal cortex, subiculum, Cornu Ammonis [CA]1, CA2, CA3, dentate gyrus, and tail) and each psychosocial factor (i.e., depressive symptoms, anxiety symptoms, childhood maltreatment, recent stressful life events, and social support), adjusted for age, sex, and intracranial volume. Neither depression nor anxiety was associated with specific hippocampal (subfield) volumes. A trend for lower total hippocampal volume was found in those reporting childhood maltreatment, and a trend for higher total hippocampal volume was found in those who experienced a recent stressful life event. Among subfields, low social support was associated with lower volume in the CA3 (B = -0.43, 95% CI: -0.72; -0.15). This study suggests possible differential effects among hippocampal (subfield) volumes and psychosocial factors.

Achievements and Challenges of Social Epidemiology Research Aiming to Reduce Health Inequality: A Revised English Version of Japanese in the Journal of the Japan Medical Association 2020;149(9):1626-30

Health inequalities are defined as "gaps in health status between groups, which are created by differences in community or socioeconomic status." In response to the General Assembly Resolution (2009) of the World Health Organization, the World Medical Association issued a statement in the same year, and the Japanese health policy "Health Japan 21 (second term)" indicated a "reduction of health inequalities" as the basic direction. In 2000, we described the presence of health inequalities in Japan, which was regarded as a relatively egalitarian country. This was the starting point of the Japan Gerontological Evaluation Study. It was developed into large longitudinal studies that reveal the significance of "social determinants of health" that cause health inequalities. We verified the feasibility and effects of healthy aging policies by fostering social capital through community intervention studies. These findings and knowledge have been translated into municipal and central government policies. Here we review what has been achieved and the remaining challenges in more than 20 years of social epidemiological research.