Dietary Patterns and Incident Dementia in Elderly Japanese: The Ohsaki Cohort 2006 Study

A principal component analysis of metabolome and cognitive decline among Japanese older adults: cross-sectional analysis using Tohoku Medical Megabank Cohort Study

BackgroundDementia is the leading cause of disability and imposes a significant burden on society. Previous studies have suggested an association between metabolites and cognitive decline. Although the metabolite composition differs between Western and Asian populations, studies targeting Asian populations remain scarce.MethodsThis cross-sectional study used data from a cohort survey of community-dwelling older adults aged ≥ 60 years living in Miyagi, Japan, conducted by Tohoku Medical Megabank Organization between 2013 and 2016. Forty-three metabolite variables quantified using nuclear magnetic resonance spectroscopy were used as explanatory variables. Dependent variable was the presence of cognitive decline (≤ 23 points), assessed by the Mini-Mental State Examination. Principal component (PC) analysis was performed to reduce the dimensionality of metabolite variables, followed by logistic regression analysis to calculate odds ratios (ORs) and 95% confidence intervals (CIs) for cognitive decline.ResultsA total of 2,940 participants were included (men: 49.0%, mean age: 67.6 years). Among them, 1.9% showed cognitive decline. The first 12 PC components (PC1-PC12) accounted for 71.7% of the total variance. Multivariate analysis showed that PC1, which mainly represented essential amino acids, was associated with lower odds of cognitive decline (OR = 0.89; 95% CI, 0.80-0.98). PC2, which mainly included ketone bodies, was associated with cognitive decline (OR = 1.29; 95% CI, 1.11-1.51). PC3, which included amino acids, was associated with lower odds of cognitive decline (OR = 0.81; 95% CI, 0.66-0.99).ConclusionAmino acids are protectively associated with cognitive decline, whereas ketone metabolites are associated with higher odds of cognitive decline.

Ameliorating effect of Citrus trifoliata L. fruits extract on motor incoordination, neurodegeneration and oxidative stress in Parkinson's disease model

BACKGROUND

Citrus trifoliate fruit (also known as Trifoliate orange) is one of the commercially-cultivated Citrus genus of plants belonging to the Rutaceae family. It has been traditionally-utilized in treatment of neurodegenerative disorders. However, the scientific evidence verifying this utilization needs further elucidation.

AIM OF THE STUDY

Characterization of the bioactive constituents of C. trifoliata L. fruits extract and evaluating its effect on Parkinson's disease (PD) model.

MATERIAL AND METHODS

Rats were classified into 5 groups; control, PD, PD-treated by L-dopa/Carpidopa and PD-treated by oral Citrus trifoliata L. fruits extract (50 and 100 mg/kg). Deterioration in brain functions was evaluated through an in vivo open field, grid and catalepsy tests. The study also assessed the striatal neurotransmitters, oxidative stress markers and histopathological changes.

RESULTS

Citrus trifoliata L. fruit extract has revealed motor improvement comparable to L-dopa and carbidopa. It has also effectively-improved oxidative stress via reduction of striatal malondialdehyde & nitric oxide along with replenishment of the striatal glutathione and superoxide dismutase. The extract caused significant reduction of the striatal myeloperoxidase activity and restoration of dopamine, γ-amino butyric acid (GABA), and acetylcholinesterase. This effect was further confirmed by amelioration of neuronal apoptosis, microgliosis and peri-neuronal vacuolation. Metabolite profiling revealed 40 constituents, with flavonoids representing the main identified class.

CONCLUSION

The neuro-protective effect of Citrus trifoliata extract was achieved through the antioxidant and anti-inflammatory activities of its flavonoids, particularly hesperidin and naringin. This neuro-protective effect was evident at the behavioral, histological and neurotransmitter levels.

Peripheral vascular dysfunction and the aging brain

Aging is the greatest non-modifiable risk factor for most diseases, including cardiovascular diseases (CVD), which remain the leading cause of mortality worldwide. Robust evidence indicates that CVD are a strong determinant for reduced brain health and all-cause dementia with advancing age. CVD are also closely linked with peripheral and cerebral vascular dysfunction, common contributors to the development and progression of all types of dementia, that are largely driven by excessive levels of oxidative stress (e.g., reactive oxygen species [ROS]). Emerging evidence suggests that several fundamental aging mechanisms (e.g., "hallmarks" of aging), including chronic low-grade inflammation, mitochondrial dysfunction, cellular senescence and deregulated nutrient sensing contribute to excessive ROS production and are common to both peripheral and cerebral vascular dysfunction. Therefore, targeting these mechanisms to reduce ROS-related oxidative stress and improve peripheral and/or cerebral vascular function may be a promising strategy to reduce dementia risk with aging. Investigating how certain lifestyle strategies (e.g., aerobic exercise and diet modulation) and/or select pharmacological agents (natural and synthetic) intersect with aging "hallmarks" to promote peripheral and/or cerebral vascular health represent a viable option for reducing dementia risk with aging. Therefore, the primary purpose of this review is to explore mechanistic links among peripheral vascular dysfunction, cerebral vascular dysfunction, and reduced brain health with aging. Such insight and assessments of non-invasive measures of peripheral and cerebral vascular health with aging might provide a new approach for assessing dementia risk in older adults.

Risk of dementia with hearing impairment and social isolation

INTRODUCTION

This study aimed to determine whether the concomitance of hearing impairment and isolation with lack of conversation, which is considered self-evident but has not been investigated extensively, is associated with the occurrence of dementia.

METHODS

A total of 2745 participants were divided into four groups according to the presence/absence of hearing impairment and isolation with lack of conversation. The association of dementia with hearing impairment and isolation with lack of conversation was analyzed using Cox proportional hazards regression.

RESULTS

The combined hearing impairment and isolation with lack of conversation (hazard ratio: 1.69, 95% confidence interval: 1.09-2.61) and non-hearing impairment and isolation with lack of conversation (hazard ratio: 1.60, 95% confidence: 1.07-2.39) were associated with the development of dementia.

DISCUSSION

These findings emphasize the importance of promoting high-quality social relationships throughout life by adopting preventive measures against isolation with lack of conversation from the early stage of awareness of hearing impairment.

Highlights

Dementia affects 12.9% of those with hearing impairment and isolation.Hearing impairment and isolation are associated with increased risk of dementia.Addressing these risk factors may help reduce the risk of developing dementia.Preventing isolation and promoting quality social relationships is important.

Association of dietary variety with the risk for dementia: the Yabu cohort study

OBJECTIVE

The consumption of various foods is internationally recommended in healthy diet although the association between dietary variety and incident dementia is unknown. We aimed to examine the association between dietary variety and the incidence of disabling dementia in older Japanese adults.

DESIGN

We conducted a prospective cohort study. Dietary variety was assessed based on the Dietary Variety Score (DVS). DVS was assessed by counting the number of ten food components (meat, fish/shellfish, eggs, milk, soyabean products, green/yellow vegetables, potatoes, fruit, seaweed and fats/oils) that were consumed almost daily using a FFQ. Participants were categorised into low (0-2 points), middle (3-4 points) and high (5-10 points) groups based on the DVS. Data on newly diagnosed disabling dementia were retrieved from the public long-term care insurance database. Cox proportional hazards regression was used to estimate hazard ratios (HR) with 95 % CI.

SETTING

Yabu cohort study, Japan.

PARTICIPANTS

A total of 4972 community-dwelling adults aged 65 years or older.

RESULTS

During the median follow-up of 6·8 years, 884 participants were newly diagnosed with disabling dementia. After adjusting for confounders, the multivariable-adjusted HR for incident disabling dementia was 0·82 (95 % CI, 0·69, 0·97) for participants in the highest DVS category compared with those in the lowest DVS category (Pfor trend = 0·019).

CONCLUSIONS

A higher dietary variety is associated with a reduced risk of disabling dementia in older Japanese adults. These results have potential implications for the development of effective public nutritional approaches to prevent dementia in older adults.

Development of the Scores for Traditional and Modified Japanese Diets

Increasing attention is being paid to the role of diet quality in the prevention and management of non-communicable diseases. We developed a scoring system for the traditional Japanese diet and its modified version considering the dietary culture in Japan, dietary guidelines for the Japanese, and updated evidence for disease prevention. The traditional Japanese diet comprises white rice, miso soup, soybean products, vegetables, mushrooms, seaweeds, fish and shellfish, high-sodium foods, and green tea. In the modified Japanese diet, unprocessed or minimally refined rice and raw vegetables, milk and dairy products, and fruits were additionally considered, while salty food was reverse-scored. The cutoff for the intake frequency of each food/food group was determined with reference to a health survey of >12,000 workers. Among the participants in the validation study, we confirmed the nutritional gradient with increasing scores in the expected direction. The scores were closely correlated with the respondents' backgrounds, including occupational factors. This simple scoring system can be used for diet quality assessments and epidemiological research.

Nutrition and Healthy Ageing in Asia: A Systematic Review

BACKGROUND

Nutrition plays a key role in modulating the likelihood of healthy ageing. In the present study, we aimed to conduct a systematic review to assess the impact of nutrition on healthy ageing in Asia.

METHODS

The systematic review was registered in the International Prospective Register of Systematic Reviews database (CRD42023408936) and conducted based on the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. The PubMed, Web of Science, and Embase databases were searched up to February 2023 without language restrictions. We included prospective cohort studies that evaluated the associations of intake of a single food or consumption of a single nutrient at midlife; adherence to various dietary patterns at midlife; and improved adherence to dietary patterns from mid- to late life with the likelihood of healthy ageing and its components.

RESULTS

Out of 16,373 records, we included 71 papers comprising 24 cohorts from Singapore, China, Japan, and Thailand. The healthy ageing components included cognitive function, physical function, and depression. The majority of studies supported the observation that the likelihood of healthy ageing and its components in late life was positively increased by a higher consumption of healthy foods, such as vegetables, fruits, fish, nuts, legumes, tea, milk, and dairy, at midlife, and also by greater adherence to dietary patterns with high diversity scores or high total antioxidant capacities. Furthermore, improved adherence to healthy dietary patterns from mid- to late life also increased the likelihood of healthy ageing in late life.

CONCLUSION

Consuming healthy foods and adhering to healthy dietary patterns at midlife can promote the likelihood of healthy ageing. Moreover, improving diet quality from mid- to late life can still be beneficial.

Dietary diversity and risk of late-life disabling dementia in middle-aged and older adults

BACKGROUND & AIMS

A balanced diet integrating several foods and nutrients may promote the maintenance of brain function. Previous studies have substantiated the above hypothesis in the regional population in Japan. This study aimed to investigate the potential effect of dietary diversity on the risk of disabling dementia in a nationwide large-scale cohort of the Japanese population.

METHODS

A total of 38,797 participants (17,708 men and 21,089 women) aged 45-74 years were followed up for a median of 11.0 years. The daily frequencies of the consumption of each of the 133 food and beverage items listed on a food frequency questionnaire (excluding five alcoholic beverages) were measured. The dietary diversity score was calculated as the number of food items consumed per day. Multivariable adjusted Cox proportional hazards regression models were used to calculate hazard ratios (HRs) and corresponding 95% confidence intervals (CIs) of the dietary diversity score quintile groups.

RESULTS

We documented 4302 participants with disabling dementia (11.1%) during the follow-up period. Among women, the dietary diversity score was inversely associated with disabling dementia (highest quintile HR [with the lowest quintile as the reference]: 0.67; 95% CI: 0.56-0.78; Q1-Q5 p for trend <0.001), but this was not true among men (highest quintile HR: 1.06; 95% CI: 0.87-1.29; Q1-Q5 p for trend = 0.415). These results did not change substantially when using disabling dementia with stroke as the outcome; the association remained significant among women but was absent among men.

CONCLUSIONS

Our findings indicate that eating a variety of foods may prevent disabling dementia only among women. Thus, the habit of consuming a variety of food items has important public health implications for women.

Prospective Study of Diet Quality and the Risk of Dementia in the Oldest Old

This study examined the associations between overall diet quality and the risk of dementia in a rural cohort among the oldest old. Included in this prospective cohort study were 2232 participants aged ≥ 80 years and dementia-free at the baseline according to the Geisinger Rural Aging Study (GRAS), a longitudinal cohort in rural Pennsylvania. In 2009, diet quality was assessed by a validated dietary screening tool (DST). Incident cases of dementia during 2009-2021 were identified using diagnosis codes. This approach was validated by a review of electronic health records. Associations between diet quality scores and the incidence of dementia were estimated using the Cox proportional hazards models, adjusted for potential confounders. Across a mean of 6.90 years of follow-up, we identified 408 incident cases of all-cause dementia. Having a higher diet quality was not significantly associated with a lower risk for incidents of all-cause dementia (adjusted HR for the highest compared with the lowest tertile: 1.01, 95% CI: 0.79, 1.29, P-trend = 0.95). Similarly, we did not observe a significant association between diet quality and altered risks of Alzheimer's disease and other forms of dementia. Overall, having a higher diet quality was not significantly associated with a lower risk of dementia among the oldest old during the full follow-up.

Twenty-year prospective cohort study of the association between a Japanese dietary pattern and incident dementia: the NILS-LSA project

PURPOSE

Evidence has suggested that adherence to a Japanese diet may be beneficial for health. However, its association with incident dementia remains unclear. The aim was to explore this association in older Japanese community-dwellers, taking apoprotein E genotype into consideration.

METHODS

A 20-year follow-up cohort study involving 1504 dementia-free older Japanese community-dwellers (aged 65-82 years) living in Aichi Prefecture, Japan, was conducted. Based on a previous study, a 9-component-weighted Japanese Diet Index (wJDI9) score (range - 1 to 12) was calculated using 3-day dietary record data and used as an indicator of adherence to a Japanese diet. Incident dementia was confirmed by the Long-term Care Insurance System certificate, and dementia events occurring within the first 5 years of follow-up were excluded. A multivariate-adjusted Cox proportional hazards model was used to calculate hazard ratios (HRs) and 95% confidence intervals (CIs) for incident dementia, and Laplace regression was used to estimate percentile differences (PDs) and 95% CIs (expressed in months) in age at incident dementia (i.e., dementia-free duration differences), according to tertiles (T1-T3) of wJDI9 scores.

RESULTS

The median (IQR) follow-up duration was 11.4 (7.8-15.1) years. During the follow-up period, 225 (15.0%) cases of incident dementia were identified. Because the smallest prevalence of incident dementia was 10.7% for the T3 group of wJDI9 scores, to avoid inaccurately estimating the dementia-free duration of participants in the T3 group, the 11th PDs in age at incident dementia between the T1 and T3 groups of wJDI9 scores were estimated. A higher wJDI9 score was associated with a lower risk of incident dementia and a longer dementia-free duration difference. The multivariate-adjusted HR (95% CI) and 11th PDs (95% CI) in age at incident dementia for participants in the T1 vs. T3 group were 1.00 (reference) vs. 0.58 (0.40, 0.86), and 0 (reference) vs. 36.7 (9.9, 63.4) months, respectively. Each 1-point increase of the wJDI9 score was associated with a 5% lower risk of incident dementia (P value = 0.033) and 3.9 (0.3, 7.6) additional months of dementia-free duration (P value = 0.035). No differences were seen in sex or smoking status (current smoker vs. non-current smoker) at baseline.

CONCLUSION

These findings suggest that adherence to a Japanese diet defined by wJDI9 is associated with a lower risk of incident dementia in older Japanese community-dwellers, suggesting the benefit of the Japanese diet for dementia prevention.

Japanese carotenoid database with α- and β-carotene, β-cryptoxanthin, lutein, zeaxanthin, lycopene, and fucoxanthin and intake in adult women

Carotenoid intake is associated with low mortality and cancer risks; data on non-provitamin carotenoid intake is limited especially in Asians. We aimed to estimate carotenoid intake in Japanese adult women. Carotenoid content database comprises 196 food items, including 39 fruits, 87 vegetables and mushrooms, and 11 seaweeds, and was established using data from the literature and analyses of foods available in Japan. We surveyed the intake of these foods in Japanese women aged 21-56 years (n=109). Total intake of 7 carotenoids (mean±SD [range]) was 7,450±3,840 (1,160-21,300) μg/day; α-carotene, β-carotene, β-cryptoxanthin, lutein, zeaxanthin, lycopene, and fucoxanthin represented 4.3%, 23%, 3.4%, 15%, 2.0%, 39%, and 13% of total intake, respectively. Lutein intake was 1,132±686 (294-3,490) μg/day; its best sources were spinach, cucumber, chicken egg, green onion, and Chinese chives, representing 51% of total intake. Lutein can be obtained from a variety of sources. Thus, lutein intake levels did not vary widely among individuals and very few individuals consumed insufficient levels of lutein. Intake of zeaxanthin, lycopene, and fucoxanthin was 149±93 (2-479), 2,890±2,970 (0-17,100), and 980±1,230 (0-5,660) μg/day, respectively. Their intake required rich sources including chicken egg for zeaxanthin (52%); tomato products for lycopene (98%), and wakame seaweed for fucoxanthin (76%). The carotenoid content database including all food items consumed in Japan will be helpful for further investigations on carotenoid intake and its health benefits.

Cognitive Decline Related to Diet Pattern and Nutritional Adequacy in Alzheimer's Disease Using Surface-Based Morphometry

Dietary pattern (DP) results in nutrition adequacy and may influence cognitive decline and cortical atrophy in Alzheimer's disease (AD). The study explored DP in 248 patients with AD. Two neurobehavioral assessments (intervals 13.4 months) and two cortical thickness measurements derived from magnetic resonance images (intervals 26.5 months) were collected as outcome measures. Reduced rank regression was used to assess the groups of DPs and a linear mixed-effect model to explore the cortical neurodegenerative patterns. At screening, underweight body mass index (BMI) was related to significant higher lipid profile, impaired cognitive function, smaller cortical thickness, lower protein DP factor loading scores and the non-spouse caregiver status. Higher mini-mental state examination (MMSE) scores were related to the DP of coffee/tea, compared to the lipid/sugar or protein DP group. The underweighted-BMI group had faster cortical thickness atrophy in the pregenual and lateral temporal cortex, while the correlations between cortical thickness degeneration and high HbA1C or low B12 and folate levels were localized in the medial and lateral prefrontal cortex. The predictive model suggested that factors related to MMSE score were related to the caregiver status. In conclusion, normal or overweight BMI, coffee/tea DP group and living with a spouse were considered as protective factors for better cognitive outcomes in patients with AD. The influence of glucose, B12 and folate on the cortical degeneration was spatially distinct from the pattern of AD degeneration.

Dietary Patterns and New-Onset Type 2 Diabetes Mellitus in Evacuees after the Great East Japan Earthquake: A 7-Year Longitudinal Analysis in the Fukushima Health Management Survey

Background: Dietary patterns may be linked to the incidence of type 2 diabetes mellitus (T2DM) after disasters. We investigated the association between dietary patterns and new-onset T2DM in evacuees of the Great East Japan Earthquake and the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident. Methods: Among the 22,740 non-diabetic participants aged 20-89 years who completed the dietary assessment in the Fukushima Health Management Survey between July 2011 and November 2012, the incidence of T2DM was evaluated until 2018. Principal component analysis with varimax rotation was applied to derive dietary patterns based on a validated, short-form food frequency questionnaire. The identified dietary patterns were categorized as typical Japanese, juice, and meat. Results: The cumulative incidence of T2DM was 18.0 and 9.8 per 1000 person-years in men and women, respectively, during the follow-up period. The multiple-adjusted hazard ratio (95% confidence interval) of the highest vs. lowest quartile of the typical Japanese pattern scores for T2DM was 0.80 (0.68, 0.94; P for trend = 0.015) in total, 0.85 (0.68, 1.06; P for trend = 0.181) in men, and 0.76 (0.60, 0.95; P for trend = 0.04) in women. Conclusions: A typical Japanese dietary pattern may be associated with a reduced new-onset T2DM risk in evacuees, especially women, after the Great East Japan Earthquake and the FDNPP accident.

Association of Japanese and Mediterranean Dietary Patterns with Muscle Weakness in Japanese Community-Dwelling Middle-Aged and Older Adults: Post Hoc Cross-Sectional Analysis

The association of Japanese and Mediterranean dietary patterns with muscle weakness in middle-aged and older Japanese individuals is unclear. This cross-sectional study investigated the association between Japanese and Mediterranean dietary patterns and muscle weakness in community-dwelling, middle-aged, and older Japanese individuals (enrolled from 2007 to 2011). Based on the dietary consumption information obtained from the brief self-administered diet history questionnaire, we assessed adherence to the Japanese (12-component revised Japanese diet index (rJDI12)) and Mediterranean (alternate Mediterranean diet (aMed) score) dietary patterns. Muscle weakness was defined as handgrip strength <28 and <18 kg for men and women, respectively. Logistic regression was used to ascertain the relationship between dietary pattern and muscle weakness. In our study, with 6031 participants, the Japanese, but not Mediterranean, dietary pattern was inversely associated with muscle weakness (p for trend = 0.031 and 0.242, respectively). In the model adjusted for confounders, including energy intake, the highest quartile of rJDI12 scores (9-12 points), and the rJDI12 scores, entered as continuous variables, showed an independent association (odds ratio (95% CI), 0.703 (0.507-0.974), and 0.933 (0.891-0.977), respectively). Our findings showed that adherence to the Japanese dietary pattern is associated with a low prevalence of muscle weakness.

Diet, nutrition, and cognitive function: A narrative review of Japanese longitudinal studies

In aging societies, the number of older people with cognitive decline and dementia is increasing. Proper nutrition is a key factor that can help in the prevention of these age-related impairments. This narrative review of longitudinal studies in Japan outlines the relationship between nutrition and the brain and focuses on Japanese nutritional epidemiologic studies. The results of Japanese cohort studies suggest that rather than a single food or nutrient, a nutritionally balanced diet that integrates a variety of foods and nutrients can contribute to the maintenance of brain function and be effective in preventing dementia. In addition, this review considers a nutritional approach to reducing the severity of cognitive decline in individuals with mild cognitive impairment and dementia, and suggests lifelong strategies for the prevention of cognitive decline. It is important that we consider the practice of eating not only as a way to obtain nutrients, but also as an important lifestyle habit to maintain our physical and mental health. Geriatr Gerontol Int 2022; 22: 825-831.

Association of eating habits and Firmicutes/Bacteroidetes ratio among Japanese female university students: A cross-sectional study

Background & Aims: University students are prone to changes in their health status and lifestyle due to changes in their living environment and associated stress and anxiety. These changes may affect them in later life. This study utilized a cross-sectional study among Japanese female university students to examine dietary factors affecting their fecal microbiota. Methods: Sixty-eight healthy female university students were evaluated using an eating behavior assessment and diet history questionnaire. The 12-component Japanese diet index (JDI-12) was then calculated. A quantitative real-time PCR method was used to analyze the predominant bacterial species in the gut, and the Firmicutes/Bacteroidetes ratio (F/B ratio) at the phylum level was calculated. The partial correlation between the fecal microbiota and eating behavior abnormality score was assessed, and dietary habits associated with the F/B ratio were analyzed. Results: A significant correlation was identified between F/B ratios and the eating behavior abnormality score (r = 0.26, FDR = 0.064). Additionally, multiple regression analysis identified a negative correlation trend between the F/B ratio and JDI-12 score (β = -0.22; p = 0.091), and exploratory analysis found a negative association between the F/B ratio and consumption of beef and pork, one of the less beneficial JDI-12 components (β = -0.33, FDR = 0.120). Conclusion: In healthy female university students, there was a positive correlation between eating behavior abnormality and the F/B ratio, indicating that adherence to the Japanese diet pattern may be associated with a lower F/B ratio.

Relationships between Food Production Experience and the Behavior, Attitude, and Knowledge of Dietary Recommendations among Japanese Adults: A Cross-Sectional Study

The Japanese Ministry of Agriculture, Forestry, and Fisheries proposed to educate more people in food production as one of the objectives of the Basic Plan for Food and Nutrition Education Promotion. This cross-sectional study aims to elucidate the relationship between food production experience (agricultural, forestry, and fishery experiences) and the behavior, attitude, and knowledge of dietary recommendations among Japanese adults. This study was conducted using data obtained from the “Survey on Dietary Habits and Agriculture, Forestry, and Fishery Experiences (2019)”. This survey was conducted by mailing paper questionnaires to respondents aged 20–69 years living in 17 regions across Japan. The independent variable was food production experience. The dependent variables were each of the 13 goals of the dietary guidelines in Japan, the total score for adherence to the 13 items (low scores indicate good adherence), adherence to a Japanese-style diet, and four items on the attitude and knowledge of dietary recommendations. I also examined the association between the point in life the food production experience occurred and the above outcomes. The data obtained from 3461 participants aged 20 to 69 years were used for multivariate logistic and linear regression analyses. Food production experience was positively associated with an improved behavior, attitude, and knowledge of dietary recommendations among adults in Japan. The study found a strong relationship with food production experiences in adulthood.

Japanese Diet and Mortality, Disability, and Dementia: Evidence from the Ohsaki Cohort Study

The Japanese dietary pattern has long been discussed as one of the factors behind the longevity of Japanese people. However, the health benefits of the Japanese dietary pattern have not been fully elucidated. We published the first report in the world regarding the relation between the Japanese dietary pattern and cardiovascular disease mortality in 2007 using cohort studies including Japanese residents of Ohsaki City, Miyagi Prefecture, Japan. Since then, we have developed the Japanese Diet Index (JDI) that was based on previous findings to assess the degree of the Japanese dietary pattern and to advance the evidence on the health effects of the Japanese dietary pattern. So far, we have explored the associations between the JDI score (in quartiles) and various outcomes. For all-cause mortality, in comparison to Q1 (the lowest), the multivariable hazard ratios (HRs) and 95% confidence intervals (95%CIs) were 0.92 (0.85–1.00) for Q2, 0.91 (0.83–0.99) for Q3, and 0.91 (0.83–0.99) for Q4 (the highest). For functional disability, the multivariable HRs (95%CIs) were 0.94 (0.81–1.09) for Q2, 0.90 (0.77–1.05) for Q3, and 0.79 (0.68–0.92) for Q4. For dementia, the multivariable HRs (95%CIs) were 0.88 (0.74–1.05) for Q2, 0.87 (0.73–1.04) for Q3, 0.79 (0.66–0.95) for Q4. In addition, people with higher adherence to the Japanese dietary pattern also showed decreases in disability and dementia risks. The purpose of this article was to review all six papers, summarize the health effects of the Japanese dietary pattern, and discuss implications for future research.

Joint effect of cognitive decline and walking ability on incidence of wandering behavior in older adults with dementia: A cohort study

OBJECTIVES

Wandering behavior is one of the most troublesome behavioral disturbances in dementia. Inconsistent associations between physical function and wandering behavior were reported, and the effect of cognitive decline may be different according to walking ability. The purposes of this study are to investigate whether high walking ability is a risk factor for wandering behavior and to investigate the interaction of walking ability and cognitive function with wandering behavior in older adults with dementia.

METHODS

This retrospective cohort study included 3979 elderly adults with dementia. The association of cognitive function and walking ability with incidence of wandering behavior during a 5-year follow-up period were examined using a generalized linear model, and relative excess risk due to interaction (RERI) was calculated.

RESULTS

Severe cognitive decline and high walking ability were associated with a higher risk for wandering behavior. Additionally, some joint effects of cognitive decline and walking ability decline were higher than the sum of its individual effects (RERI [95% confidence interval], severe cognitive decline × 'walk with help': 1.58 [0.35, 2.81]; severe cognitive decline × 'independent': 3.09 [1.05, 5.14]).

CONCLUSIONS

Effects of cognitive decline and walking ability on incidence of wandering behavior were observed, and the effects varied depending on their combination.

Risk Factors of Long-Term Care Insurance Certification in Japan: A Scoping Review

This study aimed to review evidence on future long-term care associated with pre-existing factors among community-dwelling Japanese older adults. We systematically searched cohort and nested case–control studies published between 2000 and 2019 that assessed long-term care certification using the PubMed, CINAHL, and EMBASE databases. The relationship between long-term care insurance information and risk factors was investigated. The protocol was registered with the Open Science Framework. We extracted 91 studies for synthesis, including 84 prospective cohort studies, 1 retrospective cohort study, and 6 nested case–control studies. Certification for long-term care was classified into two endpoints: onset of functional disability and dementia. There were 72 studies that used long-term care certification as a proxy for functional disability, and 22 used long-term care information to indicate the onset of dementia. Common risk factors related to functional disability were physical function, frailty, and oral condition. Motor function and nutritional status were common risk factors for dementia. We found consistent associations between premorbid risk factors and functional disability and dementia. The accumulation of evidence on the incidence of long-term care and associated factors can aid the development of preventive measures. Future studies should aim to integrate this evidence.

Soy consumption, cognitive function, and dementia

PURPOSE OF REVIEW

With the rising number of people living with dementia, the interest in modifiable risk factors including dietary intake for dementia is increasing. Although there is a growing body of evidence investigating soy's health effects, the direction and strength of the association between soy consumption and risk of dementia and cognitive decline are still uncertain. Thus, we aimed to review the evidence linking soy consumption to dementia and cognitive function.

RECENT FINDINGS

Some studies showed that higher intake of total soy products was associated with a lower risk or prevalence of cognitive impairment. Some studies pointed to an inverse association between higher tofu consumption and cognitive function, whereas a higher intake of soybean was associated with better cognitive function.

SUMMARY

Previous studies are scarce and have provided contradictory results. Soy is a high-protein alternative to red meat and processed meat. Further studies are needed to clarify the safety and potential preventive effects particularly in healthy populations before clinical disease manifestation and irreversible injury have occurred.

Relationship between the Japanese-style diet, gut microbiota, and dementia: A cross-sectional study

OBJECTIVE

Previous studies have shown associations between the gut microbiota, microbial metabolites, and cognitive decline. However, the effect of the dietary composition on such associations has not been fully investigated. The aims of this study were to evaluate the relationships between adherence to a Japanese-style diet, the gut microbiota, and cognitive decline. Furthermore, we aimed to evaluate the three forms of the Japanese diet index (JDI; the conventional [JDI₉], updated [JDI₁₂], and a newly modified JDI) to determine which would show the closest relationships with cognition and the gut microbiota.

METHODS

We performed a cross-sectional subanalysis of data from a prospective hospital-based cohort study. We assessed the patients' demographic characteristics, dietary composition, risk factors, cognitive function, brain imaging, gut microbiome, and microbial metabolites. On the basis of previous studies, a nine-component traditional JDI (JDI₉), a 12-component modern JDI (JDI₁₂), and a 12-component revised JDI (rJDI₁₂), were defined. We evaluated the relationships between the JDI scores, cognitive function, and the gut microbiome and microbial metabolites using multivariable logistic regression analyses.

RESULTS

We analyzed data from 85 eligible participants (61% women; mean age: 74.6 ± 7.4 y). Compared with participants who had dementia, those without dementia were more likely to consume foods in the JDI₁₂, including fish and shellfish (64.5 versus 39.1%, P = 0.048), mushrooms (61.3 versus 30.4%, P = 0.015), soybeans and soybean-derived foods (62.9 versus 30.4%, P = 0.013), and coffee (71 versus 43.5%, P = 0.024). There were non-significant trends toward lower fecal concentrations of gut microbial metabolites in participants with a more traditional Japanese diet. Participants with dementia had lower JDI scores than those without dementia (dementia versus non-dementia, median JDI₉ score: 5 versus 7, P = 0.049; JDI₁₂: 7 versus 8, P = 0.017; and rJDI₁₂: 7 versus 9, P = 0.006, respectively).

CONCLUSIONS

Adherence to a traditional Japanese diet was found to be inversely associated with cognitive decline and tended to be associated with lower concentrations of gut microbial metabolites.

Dietary Pattern, Diet Quality, and Dementia: A Systematic Review and Meta-Analysis of Prospective Cohort Studies

BACKGROUND

Diet is an important lifestyle factor that may prevent or slow the onset and progression of neurodegeneration. Some, but not all, recent studies have suggested that adherence to a healthy dietary pattern may be associated with reduced risk of dementia.

OBJECTIVE

In this meta-analysis, we systematically examined the associations between overall dietary patterns, assessed a priori and a posteriori, and risk of dementia.

METHODS

We systematically searched PubMed, Web of Science, and the Cumulative Index for Nursing and Allied Health databases from January 1, 1981 to September 11, 2019. Prospective studies published in English were included. Random-effects model was used to calculate the pooled risk ratios and 95% confidence intervals (CIs).

RESULTS

Sixteen research articles were identified in the systematic review and 12 research articles including 66,930 participants were further included for the meta-analysis. Adherence to high diet quality or a healthy dietary pattern was significantly associated with lower risk of overall dementia (pooled risk ratio = 0.82; 95% CI: 0.70, 0.95; n = 12) and Alzheimer's disease (pooled risk ratio = 0.61; 95% CI: 0.47, 0.79; n = 6) relative to those with low diet quality or an unhealthy dietary pattern. Subgroup analyses stratified by age, sex, follow-up duration, diet quality assessment approach, study location, and study quality generated similar results.

CONCLUSION

Adherence to a healthy dietary pattern was associated with lower risk of overall dementia. Further randomized controlled trials are needed to provide additional evidence about the role of a healthy diet on the development and progression of dementia.

Frequency of consumption of balanced meals, bodyweight gain and incident risk of glucose intolerance in Japanese men and women: A cohort study

AIMS/INTRODUCTION

This cohort study assessed the risk for bodyweight gain and development of glucose intolerance based on the frequency of consumption of balanced meals including grain, fish or meat and vegetables.

MATERIALS AND METHODS

The participants (8,573 men, 3,327 women) were employees of a company in Japan. A self-administered questionnaire was used to evaluate the frequency of balanced meal consumption. Bodyweight changes and the incidence of glucose intolerance (glycated hemoglobin >6.0%) during the 3-year follow-up period were determined through annual health examinations.

RESULTS

The mean bodyweight change over a period of 3 years was 0.78 kg for men and 0.84 kg for women. A lower frequency of balanced meals was associated with a higher bodyweight gain for men (P for trend = 0.004), but not for women. During the study, 464 men and 115 women developed glucose intolerance. Overall, the frequency of balanced meals was not associated with the risk of glucose intolerance in either sex. However, the interaction between the frequency of balanced meals and degree of obesity had a significant effect on the incidence of glucose intolerance in men (P = 0.005), with less frequent consumption of balanced meals being associated with a higher risk for glucose intolerance among men with a BMI ≥25.0 kg/m2 (P for trend = 0.007).

CONCLUSIONS

A higher frequency of balanced meals, including grain, fish or meat and vegetable dishes - important components of healthy Japanese food - was associated with a lower risk of glucose intolerance in obese men, but not in non-obese men and women.

Dietary Patterns and Progression of Impaired Kidney Function in Japanese Adults: A Longitudinal Analysis for the Fukushima Health Management Survey, 2011-2015

To investigate associations between dietary patterns and the risk of impaired kidney function, we analyzed data from 14,732 participants (40–89 years) who completed the baseline diet questionnaire of The Fukushima Health Management Survey in 2011. The incidence of chronic kidney disease (CKD) (estimated glomerular filtration rate (eGFR) <60 mL/min/1.73 m² or proteinuria (≥1+ by dipstick test)) and annual changes in eGFR were assessed from 2012 to 2015. Three major dietary patterns were identified. The adjusted cumulative incidence ratio of the highest vs. lowest tertile of a vegetable diet scores was 0.90 (95% confidence interval (CI): 0.82, 1.00) for eGFR < 60 mL/min/1.73 m², 0.68 (95% CI: 0.52, 0.90) for proteinuria, and 0.88 (95% CI: 0.80, 0.97) for CKD (P for trend = 0.031, 0.007, and 0.005, respectively). The incident risk of CKD in the highest tertile of juice diet scores was 18% higher than the lowest tertile. The odds ratio of the highest vs. lowest tertile of vegetable diet scores was 0.85 (95% CI: 0.75, 0.98) in the rapidly decreasing eGFR group (P for trend = 0.009). We did not observe significant associations for the meat dietary pattern. A Japanese vegetable diet could reduce the risk of developing impaired kidney function and CKD.

Changes in a specific dietary pattern and incident dementia: A prospective cohort study

BACKGROUND & AIMS

Previous studies have reported that the Japanese diet is associated with a lower risk of dementia; however, whether changes in adherence to the Japanese diet affects incident dementia remains unknown. We aimed to evaluate the association between long-term changes in adherence to the Japanese diet and risk of incident dementia among older Japanese individuals.

METHODS

We collected dietary information from community-dwelling older individuals living in Ohsaki city, Japan using a validated 39-item food frequency questionnaire in 1994 and 2006. Adherence to the Japanese diet was assessed using the 8-item Japanese Diet Index (JDI8) score (range: 0 to 8 points). Changes in adherence to the Japanese diet were defined as changes in the JDI8 score from 1994 to 2006. Next, the participants were classified into five groups: great decrease, moderate decrease, no changes [ref.], moderate increase, or great increase. Then, 3146 Japanese adults aged ≥65 years in 2006 were followed-up for 5.7 years. Incident dementia was retrieved from the long-term care insurance database. The Cox proportional hazards model was used to estimate multivariable-adjusted hazard ratios (HRs) and 95% confidence intervals (95% CIs) for incident dementia.

RESULTS

During 14,336 person-years of follow up, 231 cases of dementia were ascertained. Compared with no changes in the JDI8 score, the multivariable-adjusted HRs (95%CIs) were 1.72 (1.13, 2.62) for great decrease, 1.10 (0.73, 1.66) for moderate decrease, 0.82 (0.54, 1.25) for moderate increase, and 0.62 (0.38, 1.02) for great increase (p-trend <0.0001).

CONCLUSIONS

An increase in adherence to the Japanese diet was associated with a reduced risk of incident dementia, whereas a decrease in adherence was associated with an elevated risk among older Japanese individuals.

Is milk and dairy intake a preventive factor for elderly cognition (dementia and Alzheimer's)? A quality review of cohort surveys

Milk and dairy (M&D) is a longstanding human food with widespread use. Many studies showed the preventive capacity of M&D in several human health disorders, but its utility in others is under discussion. Aging has been associated to elderly cognitive decline including dementia-Alzheimer syndrome (Dem-AD). The absence of a therapy to impede or postpone Dem-AD determines the need for its prevention, including nutritional factors. To evaluate the preventive capacity of M&D consumption in elderly Dem-AD we performed a systematic review in the main biomedical databases and information resources, but we present this study as a narrative review to discuss better the complexity of this subject. The elderly Dem-AD has a long pre-symptomatic period and the M&D intake has a widespread use. These determinants and the quality flaws of published studies impeach us to answer whether M&D consumption is preventive for Dem-AD. Moreover, two long Japanese cohorts suggest that M&D intake could prevent Dem-AD. Prospective cohorts beginning in midlife (or early life) could answer this question in the future.

Lipid Peroxidation and Antioxidant Supplementation in Neurodegenerative Diseases: A Review of Human Studies

Being characterized by progressive and severe damage in neuronal cells, neurodegenerative diseases (NDDs) are the major cause of disability and morbidity in the elderly, imposing a significant economic and social burden. As major components of the central nervous system, lipids play important roles in neural health and pathology. Disturbed lipid metabolism, particularly lipid peroxidation (LPO), is associated with the development of many NDDs, including Alzheimer’s disease (AD), Parkinson’s disease (PD), and amyotrophic lateral sclerosis (ALS), all of which show elevated levels of LPO products and LPO-modified proteins. Thus, the inhibition of neuronal oxidation might slow the progression and reduce the severity of NDD; natural antioxidants, such as polyphenols and antioxidant vitamins, seem to be the most promising agents. Here, we summarize current literature data that were derived from human studies on the effect of natural polyphenols and vitamins A, C, and E supplementation in patients with AD, PD, and ALS. Although these compounds may reduce the severity and slow the progression of NDD, research gaps remain in antioxidants supplementation in AD, PD, and ALS patients, which indicates that further human studies applying antioxidant supplementation in different forms of NDDs are urgently needed.

Soy intake and chronic disease risk: findings from prospective cohort studies in Japan

There has been much interest in the potential role of soy in reducing the risk of chronic diseases. Soy foods are uniquely rich in isoflavones, a fact that has triggered much research including intervention studies. However, there have been few long-term prospective observational studies that include disease itself as an outcome. High intake of soy foods is intrinsic to the Japanese diet, which can be advantageous for conducting such studies in Japan. The present report reviews the findings from Japanese prospective cohort studies on soy intake and the risk of cardiovascular diseases, cancer, type 2 diabetes, osteoporosis, menopausal symptoms, and dementia. The results suggest a beneficial role of soy in several chronic diseases, but they are not without controversy. Discrepancies have been observed in the findings of studies of Japanese or other Asians as compared to those of non Asians. This review discusses the issues to be explored in future studies.

Associations between Dietary Patterns and Cardiometabolic Risks in Japan: A Cross-Sectional Study from the Fukushima Health Management Survey, 2011-2015

Cardiometabolic risks were increasing in Fukushima residents after the Great East Japan Earthquake. We examined the association between dietary patterns and cardiometabolic risks in those aged ≥16 years. Dietary patterns were derived by principal component analysis for participants who underwent at least one diet assessment using a short-form food frequency questionnaire during 2011–2013 and a health checkup in 2014 and 2015 (n = 15,409 and 14,999, respectively). In 2014, the adjusted prevalence ratio (PR) and 95% confidence interval (CI) in the highest versus lowest quartile of accumulative mean scores were 0.97 (0.96–0.99) for overweight/obesity, 0.96 (0.95–0.97) for total cholesterol (TC) ≥ 220 mg/dL, 0.96 (0.95–0.98) for low-density lipoprotein cholesterol (LDL-C) ≥ 140 mg/dL, and 0.97 (0.96–0.99) for triglycerides ≥ 150 mg/dL for a vegetable diet and 1.03 (1.01–1.04) for TC ≥ 220 mg/dL and 1.02 (1.01–1.04) for LDL-C ≥ 140 mg/dL for a juice/milk diet. In 2015, we found consistently significant associations for the vegetable and juice/milk diets, and the PR and 95% CI were 0.99 (0.98–1.00) for HDL-C < 40 mg/dL for a meat diet. The continuous promotion of the vegetable pattern diet is necessary to reduce cardiometabolic risks, particularly dyslipidemia, in Japan.

Association between Traditional Japanese Diet Washoku and Sarcopenia in Community-Dwelling Older Adults: Findings from the Kashiwa Study

OBJECTIVES

To identify the dietary patterns among community-dwelling Japanese older adults and to explore the association between these patterns and sarcopenia.

DESIGN

Cross-sectional study.

SETTING

Kashiwa city, Chiba prefecture, Japan.

PARTICIPANTS

Community-dwelling older adults (n = 1241) aged 65 years and over who were not eligible for long-term care.

MEASUREMENTS

Dietary intake was assessed using the brief self-administered diet history questionnaire (BDHQ). Dietary patterns were identified using both principal component analysis and the score on the Japanese diet comprising soybeans and soybean products, fish, vegetables, pickles, mushroom, seaweeds, and fruits. Sarcopenia was defined by the Asian Working Group for Sarcopenia (AWGS) criteria. A binary logistic regression analysis was performed with sarcopenia status as the dependent variable after adjusting for economic status, living alone status, BMI, energy intake, multimorbidity, and physical activity.

RESULTS

Participants' mean age was 74.6 years, and 52.1% were male. According to AWGS criteria, 5.1% had sarcopenia. Three dietary patterns were identified from the principal component analysis. Dietary pattern 1 (DP1), showed high loadings for fish, tofu, vegetables, and fruits which are similar to the side dishes in a typical Japanese diet. Dietary pattern 2 (DP2) had high factor loadings for fish, rice, and miso soup which are main dishes in a typical Japanese diet. Dietary pattern 3 (DP3) had a high factor loading for noodles. Men with the lowest tertile of DP1 score had a higher likelihood of being sarcopenic (Adjusted odds ratio (AOR) 3.67, 95% confidence interval (CI) 1.20-11.2). Women with the lowest tertile of DP2 score had a moderate likelihood of being sarcopenic (AOR 2.71, 95%CI 0.99-7.46). Low adherence to Japanese dietary pattern was associated with prevalence of sarcopenia in both genders.

CONCLUSION

Adherence to a dietary pattern high in foods characteristic of a Japanese diet including fish, soybean products, vegetables, and fruits was associated with low prevalence of sarcopenia in both genders.

＜Editors' Choice＞ Association between green tea intake and risk of cognitive decline, considering glycated hemoglobin level, in older Japanese adults: the NILS-LSA study

Positive and negative associations with risk of cognitive decline have been reported for glycated hemoglobin (HbA1c) level and green tea (GT) intake, respectively. This study aimed to assess whether the reduction in the risk of cognitive decline with GT intake depended on HbA1c level. The participants were aged ≥60 years at baseline in the cohort study, wherein examinations were conducted biennially from 2000 to 2012. Subjects (n=1,304) who had no cognitive decline during the first survey and who had participated in the follow-up survey at least once were included. The follow-up end point was the first screening time point for cognitive decline (Mini-Mental State Examination score <27) or the last survey participation. With reference to the Japanese Diabetes Society guideline, the cut-off points for HbA1c level were set at 5.6%, 6.0%, and 6.5%, and lower and higher groups were assigned for each cut-off point. In a multiple Cox proportional hazard model, an interaction between GT intake and HbA1c groups for cognitive decline was observed only at HbA1c 6.0% (P-value for interaction [with Bonferroni's correction] <0.05/3). Lower risks of cognitive decline were found for the HbA1c ≥5.6%, ≥6.0%, and <6.5% groups (hazard ratios: 0.59, 0.34, and 0.77; 95% confidence intervals: 0.41-0.88, 0.19-0.61, and 0.56-1.08 for "≥4 times a day" vs. "<once a day" GT intake, respectively; P-value for trend: 0.06, <0.01, and 0.09, respectively). With respect to blood glucose level, our cohort study showed non-uniformly reduced risk of cognitive decline with GT intake among older Japanese adults.

Psychological distress as a risk factor for dementia after the 2004 Niigata-Chuetsu earthquake in Japan

BACKGROUND

A large earthquake can cause extreme stress and may adversely affect cognitive function in humans. We aimed to examine a possible association between psychological distress and incident dementia after the 2004 Niigata-Chuetsu earthquake in Japan.

METHODS

This is a retrospective cohort study followed participants for 10-12 years. Subjects were 6,012 residents in 2005, 5,424 in 2006, and 5,687 in 2007 (age ≥40 years) living in Ojiya city who participated in the annual health check examinations after the 2004 Niigata-Chuetsu earthquake. Psychological distress was assessed using the Kessler Psychological Distress Scale (K10), and individuals with a K10 score ≥10 were considered to have psychological distress. Incident dementia cases were identified from a long-term care insurance database of the local government during the follow-up period. We evaluated hazard ratios (HRs) of psychological distress for incident dementia in each year, unadjusted and adjusted for covariates, including sex, age, occupation, BMI, and property damage of residential area.

RESULTS

The average age of the subjects was 64.6 years in 2005, 64.6 in 2006, and 65.2 in 2007. Adjusted HRs were significantly higher (HR = 1.20-1.66) in the psychological distress group than in the reference group in each year. In particular, adjusted HR was high (HR = 2.89) in those with psychological distress in all three years (2005-2007).

CONCLUSION

Psychological distress, especially persistent distress, is a risk factor for incident dementia in victims of large disasters.

Association between improved adherence to the Japanese diet and incident functional disability in older people: The Ohsaki Cohort 2006 Study

BACKGROUND & AIMS

Although it has been reported that the Japanese dietary pattern is associated with a lower risk of incident functional disability among older people, the potential benefits of improving adherence to the Japanese diet remain unclear. The aim of the present study was to evaluate the association between 12-year change in adherence to the Japanese diet and the subsequent risk of incident functional disability in older people in Japan.

METHODS

We analyzed 10-year follow-up data from a cohort study of 2923 Japanese older adults (age ≥65 years) in 2006. We collected dietary information using a validated 39-item food frequency questionnaire at two time points (1994 and 2006). Adherence to the Japanese diet (high intake of rice, miso soup, seaweeds, pickles, green and yellow vegetables, fish, green tea; low intake of beef and pork, and coffee) was assessed using the Japanese Diet Index (JDI), which ranges from 0 to 9. Participants were categorized into five groups according to changes in the JDI score at these two time points. Data on incident functional disability from December 2006 to November 2016 were retrieved from the public long-term care insurance database. The Cox proportional hazards model was used to estimate the hazard ratios (HRs) and 95% confidence intervals (CIs) for incident functional disability.

RESULTS

During 22,466 person-years of follow-up, 1093 cases of incident functional disability were documented. Compared with participants in the group with the largest decrease in the JDI score (≤-2), the multivariate-adjusted HR (95% CI) of incident functional disability was 0.77 (0.61-0.98) for those in the largest increase group (≥+2).

CONCLUSIONS

Improved adherence to the Japanese diet was associated with a significantly lower risk of incident functional disability in older people in Japan.

A cross-sectional study of the associations between the traditional Japanese diet and nutrient intakes: the NILS-LSA project

Background

Although our previous study using a food frequency questionnaire simulated nutritional characteristics of the traditional Japanese diet, this issue has not been sufficiently evaluated. This study was conducted to examine the relationship between the traditional Japanese diet and nutrient density (ND).

Methods

A cross-sectional study employing the dietary record method was conducted among 2221 community-dwelling Japanese adults (40–88 years) living in Aichi Prefecture, Japan, in 2006–2008. Based on previous studies, a 9-component Japanese Diet Index (JDI) and a 12-component modified JDI (mJDI₁₂) were defined. To develop a new weighted index, a multiple linear regression model was used to select food components which were significantly associated with an ND score (integrated by 11 nutrient components) from the mJDI₁₂ and weight them. Correlation analyses were performed between JDI, mJDI₁₂, the new weighted JDI score and the ND score and its 11 nutrient components. The findings were validated with data from 2008 to 2010 by assessing the associations between the JDIs scores and the ND score.

Results

Scores of the JDI and mJDI₁₂ were positively correlated with the ND score (corresponding Spearman’s ρ [95% confidence interval; CI], 0.34 [0.31, 0.38] and 0.44 [0.41, 0.48], respectively; P < 0.05 for both). Among the mJDI₁₂, 9 food components (rice, fish and shellfish, green and yellow vegetables, seaweed, green tea, beef and pork, soybeans and soybean foods, fruit, and mushrooms) significantly associated with the ND score. All of these 9 components were weighted and a new weighted JDI (wJDI₉) was developed. The wJDI₉ score was also positively correlated with the ND score (Spearman’s ρ [95% CI] = 0.61 [0.58, 0.64]; P < 0.05). However, scores for all 3 indices were positively correlated with sodium intake. The wJDI₉ score obtained using dietary record data from 2008 to 2010 was also positively correlated with the ND score (Spearman’s ρ [95% CI] = 0.61 [0.58, 0.64]; P < 0.05).

Conclusions-

Adhering to a traditional Japanese diet as defined by the JDI was associated with good ND. Furthermore, the modified indices (mJDI₁₂ and wJDI₉) had a higher performance for ND. However, all of the indices were correlated with high sodium intake.

Electronic supplementary material

The online version of this article (10.1186/s12937-019-0468-9) contains supplementary material, which is available to authorized users.

The Japanese Dietary Pattern Is Associated with Longer Disability-Free Survival Time in the General Elderly Population in the Ohsaki Cohort 2006 Study

BACKGROUND

Epidemiologic observations have raised expectations that the Japanese dietary pattern could promote longer disability-free survival (DFS) times among the Japanese population; however, no previous study has examined this issue.

OBJECTIVE

The aim of this study was to investigate the association between the Japanese dietary pattern and DFS time in the elderly Japanese population.

METHODS

We analyzed follow-up data covering a 10-y period for 9456 elderly Japanese individuals (aged ≥65 y) participating in a community-based prospective cohort study. Dietary habits were assessed using a food-frequency questionnaire. Based on previous studies, we used 9 food items to calculate the Japanese Diet Index (JDI) score: rice, miso soup, fish and shellfish, green and yellow vegetables, seaweed, pickled vegetables, green tea (1 point for each item if the consumption value was more than or equal to the median, and 0 points otherwise), beef and pork, and coffee (0 points for each item if the consumption value was more than or equal to the median, and 1 point otherwise). Differences in median age at incident disability or death [50th percentile differences (PDs)] according to quartiles (Q1-Q4) of the JDI score were estimated using Laplace regression.

RESULTS

During the follow-up period, 4233 (44.8%) incident disability or death events occurred. In addition, a higher JDI score was significantly associated with longer DFS time: compared with the lowest quartile of JDI scores (Q1), the multivariate-adjusted 50th PD (95% CI) was 7.1 (1.8, 12.4) mo longer for Q4. Each 1-SD increase of the JDI score was associated with 3.7 (1.7, 5.7) additional months of life without disability (P-trend < 0.01). No differences were seen in sex or chronic condition (no or ≥1 chronic condition) at baseline. A post hoc analysis showed a larger effect on DFS time when using a modified JDI score without coffee.

CONCLUSION

These results suggest that the Japanese dietary pattern is associated with improved DFS time in the general elderly population.

Abdominal Fat in Individuals with Overweight Reduced by Consumption of a 1975 Japanese Diet: A Randomized Controlled Trial

OBJECTIVE

This study aimed to investigate whether the intake of the 1975 Japanese diet (JD) could reduce the amount of abdominal fat in people with overweight.

METHODS

Using a single-blind randomized controlled trial, the modern diet (MD) was compared with the 1975-type JD, which is based on the MD but includes five characteristics of the 1975 JD in an enhanced form. Overweight people were randomly assigned to an MD group (n = 30) and a JD group (n = 30). The participants consumed test diets that were provided three times a day for 28 days. Body composition measurements and blood biochemical examinations were performed before and after the test diet intake, and the proportions of change were compared.

RESULTS

Those in the JD group had significantly decreased BMI, fat mass, and levels of low-density lipoprotein cholesterol, glycated hemoglobin, and C-reactive protein (P = 0.002, 0.015, 0.014, 0.012, and 0.039, respectively) and significantly increased high-density lipoprotein cholesterol levels compared with those in the MD group (P = 0.020).

CONCLUSIONS

The intake of a diet with the characteristics of the 1975 JD may have beneficial effects on lipid metabolism in people with overweight and reduce the onset risk of metabolism-related disorders, such as obesity and diabetes.

Aging, lifestyle and dementia

Aging is the greatest risk factor for most diseases including cancer, cardiovascular disorders, and neurodegenerative disease. There is emerging evidence that interventions that improve metabolic health with aging may also be effective for brain health. The most robust interventions are non-pharmacological and include limiting calorie or protein intake, increasing aerobic exercise, or environmental enrichment. In humans, dietary patterns including the Mediterranean, Finnish Geriatric Intervention Study to Prevent Cognitive Impairment and Disability (FINGER) and Okinawan diets are associated with improved age-related health and may reduce neurodegenerative disease including dementia. Rapamycin, metformin and resveratrol act on nutrient sensing pathways that improve cardiometabolic health and decrease the risk for age-associated disease. There is some evidence that they may reduce the risk for dementia in rodents. There is a growing recognition that improving metabolic function may be an effective way to optimize brain health during aging.

Analysis of the relationship between the gut microbiome and dementia: a cross-sectional study conducted in Japan

Dysregulation of the gut microbiome is associated with several life-threatening conditions and thus might represent a useful target for the prevention of dementia. However, the relationship between the gut microbial population and dementia has not yet been fully clarified. We recruited outpatients visiting our memory clinic to participate in this study. Information on patient demographics, risk factors, and activities of daily living was collected, and cognitive function was assessed using neuropsychological tests and brain magnetic resonance imaging scans. Faecal samples were obtained, and the gut microbiome was assessed by terminal restriction fragment length polymorphism (T-RFLP) analysis, one of the most well-established and reliable 16S ribosomal RNA-based methods for classifying gut microbiota. Patients were divided into two groups, demented and non-demented. Multivariable logistic regression models were used to identify the variables independently associated with dementia. The T-RFLP analysis revealed differences in the composition of the gut microbiome: the number of Bacteroides (enterotype I) was lower and the number of ‘other’ bacteria (enterotype III) was higher in demented than non-demented patients. Multivariable analyses showed that the populations of enterotype I and enterotype III bacteria were strongly associated with dementia, independent of the traditional dementia biomarkers. Further studies of the metabolites of gut microbes are needed to determine the mechanism underlying this association.

Mediators of the effects of rice intake on health in individuals consuming a traditional Japanese diet centered on rice

Although the Japanese diet is believed to be balanced and healthy, its benefits have been poorly investigated, especially in terms of effects on mental health. We investigated dietary patterns and physical and mental health in the Japanese population using an epidemiological survey to determine the health benefits of the traditional Japanese diet. Questionnaires to assess dietary habits, quality of life, sleep quality, impulsivity, and depression severity were distributed to 550 randomly selected middle-aged and elderly individuals. Participants with any physical or mental disease were excluded. Two-hundred and seventy-eight participants were selected for the final statistical analysis. We determined rice to be one of the most traditional foods in Japanese cuisine. Scores for each questionnaire were computed, and the correlations between rice intake and health indices were assessed. When analyzing the direct correlations between rice intake and health indices, we found only two correlations, namely those with quality of life (vitality) and sleep quality. Path analysis using structural equation modeling was performed to investigate the association between rice intake and health, with indirect effects included in the model. Additional associations between rice intake and health were explained using this model when compared to those using direct correlation analysis. Path analysis was used to identify mediators of the rice-health association. These mediators were miso (soybean paste) soup, green tea, and natto (fermented soybean) intake. Interestingly, these mediators have been major components of the Japanese diet since 1975, which has been considered one of the healthiest diets since the 1960s. Our results indicate that the combination of rice with other healthy foods, which is representative of the traditional Japanese diet, may contribute to improvements in physical and mental health.

Association between dietary patterns and cognitive function among 70-year-old Japanese elderly: a cross-sectional analysis of the SONIC study

BACKGROUND

An increasing number of studies in Western countries have shown that healthy dietary patterns may have a protective effect against cognitive decline and dementia. However, information on this relationship among non-Western populations with different cultural settings is extremely limited. We aim to examine the relationship between dietary patterns and cognitive function among older Japanese people.

METHODS

This cross-sectional study included 635 community-dwelling people aged 69-71 years who participated in the prospective cohort study titled Septuagenarians, Octogenarians, Nonagenarians Investigation with Centenarians (SONIC). Diet was assessed over a one-month period with a validated, brief-type, self-administered diet history questionnaire. Dietary patterns from thirty-three predefined food groups [energy-adjusted food (g/d)] were extracted by factor analysis. Cognitive function was assessed using the Japanese version of the Montreal Cognitive Assessment (MoCA-J). Multivariate regression analysis was performed to examine the relationship between dietary patterns and cognitive function.

RESULTS

Three dietary patterns were identified: the 'Plant foods and fish', 'Rice and miso soup', and 'Animal food' patterns. The 'Plant foods and fish' pattern, characterized by high intakes of green and other vegetables, soy products, seaweeds, mushrooms, potatoes, fruit, fish, and green tea, was significantly associated with a higher MoCA-J score [MoCA-J score per one-quartile increase in dietary pattern: β = 0.56 (95% CI: 0.33, 0.79), P for trend <0.001]. This association was still evident after adjustment for potential confounding factors [β = 0.41 (95% CI: 0.17, 0.65), P for trend <0.001]. In contrast, neither the 'Rice and miso soup' nor the 'Animal food' pattern was related to cognitive function. To confirm the possibility of reverse causation we also conducted a sensitivity analysis excluding 186 subjects who reported substantial changes in their diet for any reason, but the results did not change materially.

CONCLUSION

This preliminary cross-sectional study suggests that a diet with high intakes of vegetables, soy products, fruit, and fish may have a beneficial effect on cognitive function in older Japanese people. Further prospective studies are needed to confirm this finding.

Changes in time spent walking and the risk of incident dementia in older Japanese people: the Ohsaki Cohort 2006 Study

Background

the impact of long-term changes in physical activity during adulthood in the context of primary prevention of dementia has not been addressed previously.

Objective

to study the relationship between changes in time spent walking after middle age and incident dementia in older Japanese individuals.

Methodology

we conducted a cohort study of 6,909 disability-free Japanese individuals aged ≥65 years who lived in Ohsaki City, Japan. In both 1994 and 2006, the individual amount of time spent walking per day was assessed using a self-reported questionnaire (<0.5 h, 0.5-1 h or ≥1 h). Based on these three categories of exposure at the two points, participants were categorised into nine groups according to changes in time spent walking. Data on incident dementia were retrieved from the public Long-term Care Insurance (LTCI) Database, in which participants were followed up for 5.7 years (between April 2007 and November 2012). The Cox model was used for estimating the multivariate-adjusted hazard ratios (HRs) of incident dementia.

Results

the 5.7-year incidence of dementia was 9.2%. Compared with persons who remained in the lowest category of time spent walking (<0.5 h/day in both 1994 and 2006), persons who remained in the highest category (≥1 h/day in both 1994 and 2006) had a significantly lower risk of incident dementia: the multivariate-adjusted HR (95% confidence intervals) was 0.72 (0.53 and 0.97).

Conclusions

these results suggest that maintaining a higher level of physical activity after middle age may be a key strategy for prevention of dementia in older age.

Reduction of Cognitive Decline in Patients with or at High Risk for Diabetes

PURPOSE OF REVIEW

The incidence of Alzheimer's disease and related disorders is expected to triple by 2050. People with type 2 diabetes and prediabetes have a higher risk of cognitive dysfunction, including Alzheimer's disease and vascular dementia. Controversy remains about when and how to prevent and treat cognitive dysfunction in people with or at high risk of diabetes.

RECENT FINDINGS

In our review of ongoing clinical trials, we have found that there has been an increase in the number of studies assessing the efficacy of pharmacological and non-pharmacological approaches to prevent or slow down cognitive impairment among people with or at high risk of diabetes.

SUMMARY

Despite the considerable risk of cognitive impairment in people with diabetes and prediabetes, there is not enough evidence to support a specific treatment to prevent or slow mild cognitive impairment, or progression to Alzheimer's disease or related disorders. Several ongoing trials are attempting to identify the usefulness of several compounds, as well as lifestyle changes including exercise and diet. Direct mechanisms linking diabetes to cognitive decline have not been elucidated.

Prevalence of Frailty Assessed by Fried and Kihon Checklist Indexes in a Prospective Cohort Study: Design and Demographics of the Kyoto-Kameoka Longitudinal Study

OBJECTIVE

The Kyoto-Kameoka Study was launched in 2011-2012 to identify the associations among food intake, nutritional status, physical activity, oral function, quality of life or social capital, the use of long-term care insurance (LTCI) system, and healthy lifespan in community-dwelling older people as a part of the World Health Organization Safe Community program.

DESIGN

A prospective cohort study, reporting baseline demographics (cross-sectional data).

SETTING AND PARTICIPANTS

We conducted 2 mailed self-administered questionnaire surveys; one is a complete population survey with a comprehensive survey of needs in the sphere of daily life (NSDL) that included 2 different frailty indexes, the Kihon Checklist (KCL) and the Fried phenotype, socioeconomic status, general and psychological health, and social relationships; followed by the more detailed Health and Nutrition Survey. A slightly modified NSDL survey was conducted again in 2013. Survival time, LTCI certification, and medical and long-term care costs after the baseline survey will be followed.

RESULTS

Of 18,231 NSDL questionnaires distributed, 13,294 people responded (response rate: 72.92%; mean age 73.7 ± 6.4 and 75.1 ± 7.2 years for men and women, respectively; 12,054 people without and 1240 with LTCI certification). In people without LTCI, the proportion of robust, prefrail, and frail were 30.3%, 59.8%, and 9.9% in men and 25.3%, 64.7%, and 10.0% in women, according to the Fried index. The proportion of frail people as defined by KCL ≥7 was 30.8% in men and 33.3% in women.

CONCLUSIONS

The study is the first to document frailty prevalence using both Fried and KCL measures with a complete city population survey among older Japanese in the community as a part of World Health Organization Safe Community program. The study is expected to provide valuable evidence of the effects of lifestyle habits on long-term care prevention and healthy life span.

The Role of Dietary and Lifestyle Factors in Maintaining Cognitive Health

Concern over loss of cognitive function, including descent into Alzheimer's disease or dementia, grips a growing percentage of men and women worldwide as the global population ages. Many studies, though not all, suggest that maintaining cognitive health, as well as slowing and even preventing cognitive decline, dementia, and Alzheimer's disease, can be achieved by consuming healthy diets over a long enough period of time. This appears to be the case even for those who initiated dietary changes later in life, as evidenced by an intervention study assessing consumption of a healthy diet among those who were >50 years of age. All such diets share the common traits of being rich in fruits, vegetables, whole grains, and fish or seafood, while also being low in red meat and sweets. A Mediterranean-style diet shares these characteristics and has been associated with an estimated 40% lower risk of cognitive impairment, including mild cognitive impairment, dementia, and Alzheimer's disease in prospective studies, in addition to being associated with both a 65% lower risk of mild cognitive impairment and improved cognitive performance in a notable randomized controlled trial.