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.

Effect of a financial incentive (shopping point) on increasing the number of daily walking steps among community-dwelling adults in Japan: a randomised controlled trial.

OBJECTIVE: The aim of this study was to investigate the effect of a financial incentive on the number of daily walking steps among community-dwelling adults in Japan. STUDY DESIGN: Two-arm, parallel-group randomised controlled trial. SETTING/PARTICIPANTS: We recruited physically inactive community-dwelling adults from Sendai city, Japan. Eligible participants were randomly allocated to an intervention or a wait list control group. Pedometers were used to assess the mean number of daily steps in three periods: baseline (weeks 1-3), intervention (weeks 4-6) and follow-up (weeks 7-9). INTERVENTION: The intervention group was offered a financial incentive (shopping points) to meet the target number of increased daily steps in the intervention period. MAIN OUTCOME MEASURES: The primary outcome was an increase in the mean number of daily steps in the intervention and follow-up periods compared with baseline. RESULTS: Seventy-two participants (69.4% women; mean age, 61.2±16.2 years; mean number of daily steps at baseline, 6364±2804) were randomised to the intervention (n=36) and control groups (n=36). During the intervention period, the increase in mean daily steps was significantly higher in the intervention group (1650, 95% CI=1182 to 2119) than in the control group (514, 95% CI=136 to 891; p<0.001). However, the difference between groups was not significant at follow-up after the incentives were removed (p=0.311). In addition, compared with controls, a significantly higher proportion of participants in the intervention group showed an increase in mean daily steps of ≥1000 (69.4% vs 30.6%, respectively; OR=5.17, 95% CI=1.89 to 14.08). There were no adverse effects from the intervention. CONCLUSIONS: The present results suggest that financial incentives are effective in promoting short-term increases in physical activity. TRIAL REGISTRATION NUMBER: UMIN000033276.

Japanese diet and survival time: The Ohsaki Cohort 1994 study.

BACKGROUND & AIMS: Although it has been suggested that the Japanese diet contributes to the longevity of the Japanese population, no study has examined the association between the Japanese diet and survival time. The present study investigated the association between the Japanese diet and survival time. METHODS: We analyzed 20-year follow-up data from a cohort study of 14,764 Japanese men and women aged 40-79 years. At the baseline survey in 1994, we collected dietary information using a validated 40-item food frequency questionnaire. Adherence to a Japanese diet consisting of nine components (rice, miso soup, seaweeds, pickles, green and yellow vegetables, fish, green tea, beef and pork, and coffee) was assessed in terms of a Japanese dietary index (JDI) score, the total score ranging from 0 to 9. Cox proportional hazards model and Laplace regression analysis were used to estimate the hazard ratios (HRs) and differences in median age at death (50th percentile differences - PDs in age at death) with 95% confidence intervals (CIs) according to the quartiles of the JDI score. RESULTS: During the follow-up period, we documented 4,619 deaths. We observed that a higher JDI score was associated with a lower risk of mortality and longer survival time: In comparison to participants in the lowest JDI score quartile (0-4), the multivariate-adjusted HR (95% CI) of all-cause mortality was 0.91 (0.83-0.99) and the multivariate-adjusted 50th PD in age at death (95% CI) was 10.2 (3.2-17.2) months longer for those in the highest quartile (7-9). CONCLUSIONS: Adherence to a Japanese diet is associated with a longer survival time.

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.

Fish consumption and risk of incident dementia in elderly Japanese: the Ohsaki cohort 2006 study.

Fish harbour many types of nutrients that are beneficial for preventing cognitive decline. Therefore, habitual fish intake might contribute to a lower risk of incident dementia. However, few prospective cohort studies have investigated fish consumption in relation to incident dementia, and their findings have been inconsistent. To investigate the association between fish consumption and the risk of incident dementia, we collected data on the consumption of fish and other foods using an FFQ in a baseline survey of individuals aged ≥65 years living in Ohsaki City, Japan. After 5·7 years of follow-up, the incidence of dementia was 1118 (8·5 %) among 13 102 participants. We then used a multivariate-adjusted Cox model to estimate hazard ratios (HR) and 95 % CI. Compared with subjects with the lowest fish intake (Q1), the multivariate HR were 0·90 (95 % CI 0·74, 1·11) for Q2, 0·85 (95 % CI 0·73, 0·99) for Q3 and 0·84 (95 % CI 0·71, 0·997) for Q4 (Ptrend = 0·029). Such associations were also observed even after excluding participants who were diagnosed with dementia in the first 2 years of follow-up and those who had poorer cognitive function at baseline. In conclusion, an association was observed between higher fish consumption and a lower risk of incident dementia among healthy elderly people without disability. These findings suggest that habitual fish intake may be beneficial for the prevention of dementia.

Randomised controlled trial of a financial incentive for increasing the number of daily walking steps: study protocol.

INTRODUCTION: Physical activity is one of the major modifiable factors for promotion of public health. Although it has been reported that financial incentives would be effective for promoting health behaviours such as smoking cessation or attendance for cancer screening, few randomised controlled trials (RCTs) have examined the effect of financial incentives for increasing the number of daily steps among individuals in a community setting. The aim of this study is to investigate the effects of financial incentives for increasing the number of daily steps among community-dwelling adults in Japan. METHODS AND ANALYSIS: This study will be a two-arm, parallel-group RCT. We will recruit community-dwelling adults who are physically inactive in a suburban area (Nakayama) of Sendai city, Japan, using leaflets and posters. Participants that meet the inclusion criteria will be randomly allocated to an intervention group or a waitlist control group. The intervention group will be offered a financial incentive (a chance to get shopping points) if participants increase their daily steps from their baseline. The primary outcome will be the average increase in the number of daily steps (at 4-6 weeks and 7-9 weeks) relative to the average number of daily steps at the baseline (1-3 weeks). For the sample size calculation, we assumed that the difference of primary outcome would be 1302 steps. ETHICS AND DISSEMINATION: This study has been ethically approved by the research ethics committee of Tohoku University Graduate School of Medicine, Japan (No. 2018-1-171). The results will be submitted and published in a peer-reviewed scientific journal. TRIAL REGISTRATION NUMBER: UMIN000033276; Pre-results.