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Background: Although social participation has been reported to be associated with significantly lower risks of mortality and disability, to our knowledge, no study has estimated its impact on disability-free life expectancy (DFLE). Therefore, this study aimed to investigate the association between social participation and DFLE in community-dwelling older people.Methods: We analyzed 11-year follow-up data from a cohort study of 11,982 Japanese older adults (age ≥65 years) in 2006. We collected information on the number of social participations using a questionnaire. Using this information, we categorized the participants into four groups. DFLE was defined as the average number of years a person could expect to live without disability. The multistate life table method using a Markov model was employed for calculating DFLE.Results: The results revealed that DFLE according to the number of social participations was 17.8 years (95% confidence interval [CI], 17.3–18.2) for no activities, 20.9 (95% CI, 20.4–21.5) for one activity, 21.5 (95% CI, 20.9–22.0) for two activities, and 22.7 (95% CI, 22.1–23.2) for three activities in men, and 21.8 (95% CI, 21.5–22.2), 25.1 (95% CI, 24.6–25.6), 25.3 (95% CI, 24.7–25.9), and 26.7 years (95% CI, 26.1–27.4), respectively, in women. This difference in DFLE did not change after the participants were stratified for smoking, body mass index, physical activity, and depression.Conclusion: Social participation is associated with longer DFLE among Japanese older people; therefore, encouraging social participation at the population level could increase life-years lived in good health.

Background: Both weight loss and cognitive impairment are common in late-life, but it remains unknown whether weight change is associated with risk of incident dementia among elderly Japanese. Our study aimed to investigate the association between long-term weight change since midlife and risk of incident disabling dementia using a community-based cohort study of elderly Japanese.Methods: In 2006, we conducted a cohort study of 6,672 disability-free Japanese adults aged ≥65 years. In both 1994 and 2006, the participants reported their weight using a self-reported questionnaire. Based on weight obtained at these two time points, participants were classified into: stable weight (−1.4 to +1.4 kg), weight gain (≥+1.5 kg), and weight loss of −2.4 to −1.5 kg, −3.4 to −2.5 kg, −4.4 to −3.5 kg, −5.4 to −4.5 kg, and ≥−5.5 kg. Incident disabling dementia was retrieved from the public Long-term Care Insurance database. Participants were followed-up for 5.7 years (between April 2007 and November 2012). Cox proportional hazards model was used to estimate multivariable-adjusted hazard ratios (HRs) and 95% confidence intervals (CIs) for incident disabling dementia.Results: During 32,865 person-years of follow-up, 564 participants were ascertained as having incident disabling dementia. Compared with stable weight, the multivariable-adjusted HRs were 0.97 (95% CI, 0.70–1.34) for weight loss of −2.4 to −1.5 kg, 0.98 (95% CI, 0.70–1.38) for −3.4 to −2.5 kg, 1.28 (95% CI, 0.91–1.81) for −4.4 to −3.5 kg, 1.27 (95% CI, 0.92–1.77) for −5.4 to −4.5 kg, and 1.64 (95% CI, 1.29–2.09) for ≥−5.5 kg.Conclusion: Our study suggested that a ≥−3.5 kg weight loss over 12 years might be associated with higher risk of incident disabling dementia among elderly Japanese.

To examine the association between changes in sleep duration and the risk of incident dementia in the elderly. In 2006, we conducted a cohort study of 7422 disability-free Japanese individuals aged ≥65 years who lived in Ohsaki City, Japan. In both 1994 and 2006, the individual amount of sleep obtained was assessed using a self-reported questionnaire. Based on sleep duration at these two time points, participants were categorized into five groups according to the change in sleep duration. Data on incident dementia were retrieved from the public Long-term Care Insurance database, and the subjects were followed up for 5.7 years (between April 2007 and November 2012). The Cox proportional hazards model was used to estimate the multivariate-adjusted hazard ratios (HRs) and 95% confidence intervals (95% CIs) for incident dementia. During 36338 person-years of follow up, 688 cases of incident dementia were documented. Compared with subjects who had no change in sleep duration, the multivariate HRs (95% CIs) of incident dementia were 1.31 (1.07 to 1.60) for those whose sleep duration increased by 1 hr, and 2.01 (1.51 to 2.69) for an increase of ≥2 hr. Increased sleep duration is associated with a significantly higher risk of incident dementia in the elderly. Future studies using well-validated measurements are needed to confirm the association between sleep and dementia.

Background Low back pain and sleep disturbance are common health problems worldwide which are also commonly observed among people after natural disasters. These symptoms are well known to coexist, and recent reports have indicated that sleep disturbance is a risk factor for low back pain. However, the influence of low back pain on sleep disturbance has rarely been assessed; therefore, this study aimed to clarify the association of low back pain with sleep disturbance, especially focusing on the frequency of low back pain, using 3-year cohort data after the Great East Japan Earthquake. Methods This study used the data obtained from people living in the disaster-affected areas after the Great East Japan Earthquake ( n  = 2,097). Low back pain and sleep disturbance were assessed at 4, 5, 6, and 7 years after the disaster. The frequency of low back pain was defined as the number of low back pain episodes at and before the evaluation time point and categorized into five groups such as absence, 1, 2, 3, and 4 at the fourth time point and four groups such as absence, 1, 2, and 3 at the third time point. Multivariate logistic regression analyses were conducted to assess the association of low back pain with sleep disturbance. Results Low back pain was significantly associated with sleep disturbance, and the association was stronger in participants with more frequent low back pain (adjusted odds ratios [95% confidence intervals],1.46 [1.10–1.95] in “1”; 2.02 [1.49–2.74] in “2”; 2.38 [1.67–3.40] in “3”; and 4.08 [2.74–6.06] in “4” in the frequency of low back pain) ( P for trend < 0.001). Furthermore, antecedent low back pain was significantly associated with new-onset sleep disturbance, and the association was robust in more frequent low back pain (adjusted odds ratios [95% confidence intervals],1.60 [1.05–2.44] in “1”; 1.96 [1.20–3.21] in “2”; and 2.17 [1.14–4.14] in “3” in the frequency of low back pain) ( P for trend = 0.007). Conclusion Our study showed that low back pain is strongly associated with sleep disturbance. Attention should be paid to low back pain to prevent and treat sleep disturbance, especially focusing on chronicity of low back pain.

To investigate the association of smoking status and years since smoking cessation with the risk of incident dementia among elderly Japanese. We conducted a longitudinal analysis of smoking status and smoking cessation with dementia in prospective cohort study of 12,489 Japanese individuals aged ≥ 65 years who were followed up for 5.7 years. Information on smoking status and other lifestyle factors was collected via a questionnaire in 2006. Data on incident dementia were retrieved from the public Long-term Care Insurance Database. The Cox proportional hazards model was used to estimate the multivariable-adjusted hazard ratios (HRs) and 95% confidence intervals (95% CIs) for incident dementia. During 61,613 person-years of follow-up, 1110 cases (8.9%) of incident dementia were documented. Compared with individuals who had never smoked, current smokers showed a higher risk of dementia (HR 1.46, 95% CI 1.17, 1.80). Among ex-smokers, the risk for those who had stopped smoking for ≤ 2 years was still high (HR 1.39, 95% CI 0.96, 2.01), however, quitting smoking for 3 years or longer mitigated the increased risk incurred by smokers; the multivariable HRs (95% CIs) were 1.03 (0.70, 1.53) for those who had stopped smoking for 3–5 years, 1.04 (0.74, 1.45) for 6–10 years, 1.19 (0.84, 1.69) for 11–15 years, and 0.92 (0.73, 1.15) for > 15 years. Our study suggests that the risk of incident dementia among ex-smokers becomes the same level as that of never smokers if they maintain abstinence from smoking for at least 3 years.

BackgroundThe relationship between body mass index (BMI) and disability-free survival (DFS) remains unclear.MethodsWe conducted a 10-year prospective cohort study of 12,666 Japanese individuals aged ≥ 65 y. Information on BMI and lifestyle factors was collected via a questionnaire in 2006. Functional disability data were retrieved from the public Long-term Care Insurance database. Subjects were divided into seven groups according to BMI (<19, 19−21, 21−23, 23−25, 25−27, 27−29 and ≥29). Fiftieth percentile differences (PDs) and 95% confidence intervals (CIs) in the DFS period (differences of period until the first 50% of the composite outcome (disability or death) occurred in each of the BMI groups) were calculated using the Laplace regression model.ResultsThere was a U-shaped relationship between BMI and the risk of incident composite outcome, with a BMI nadir of 25−27. Based on BMI 25−27 as a reference, the 50th PDs (95% CIs) (in months) in age at disability or death (median DFS) were −20.8 (−26.4, −15.2) (P < 0.001) months for BMI <19, −13.5 (−18.2, −8.7) (P < 0.001) months for BMI 19−21, −9.8 (−14.2, −5.4) (P < 0.001) months for BMI 21−23, −2.9 (−7.5, 1.7) (P = 0.21) months for BMI 23−25, −2.7 (−8.4, 2.9) (P = 0.34) months for BMI 27−29, and −11.5 (−19.6, −3.5) (P = 0.005) months for BMI ≥ 29. These relationships did not differ by sex.ConclusionOlder individuals with a BMI of <23 or ≥29 have a significantly shorter DFS period than those with a BMI of 25−27. It is suggested that the optimal BMI range for maximization of disability-free life expectancy in the elderly population is 23−29.

Background Functional disability is a major health issue in an aging population. Low back pain (LBP) is a common health concern that can lead to functional disability in the elderly; nonetheless, their association has not yet been clarified. This study aimed to examine the association between LBP and functional disability in the elderly, with a focus on its dose-dependent effects. Methods This study used the 4-year longitudinal data of people living in disaster-affected areas after the Great East Japan Earthquake (aged ≥65,  n  = 914). LBP and physical function were assessed at 2, 4, and 6 years after the disaster. Multivariate logistic regression analyses were performed to assess the association between LBP and low physical function, as well as the effect of preceding LBP on the onset of low physical function. Results LBP was significantly associated with low physical function, and the association became stronger as the duration of LBP increased. Adjusted odds ratios (95% confidence intervals) were 1.27 (0.79–2.06) in “< 2 years,” 1.95 (1.01–3.77) in “≥2 years and <4 years,” and 2.34 (1.35–4.06) in “≥4 years” ( p for trend = 0.009). Additionally, preceding LBP was significantly associated with the onset of low physical function, and the effect became prominent as the duration of LBP increased. Adjusted odds ratios (95% confidence intervals) were 2.28 (1.19–4.37) in “< 2 years” and 2.82 (1.35–5.90) in “≥2 years” ( p for trend = 0.003). Conclusions LBP is associated with physical disability among the elderly in a dose-dependent manner. Therefore, prevention and treatment of LBP are important for preventing functional disability.

The effect of body mass index (BMI) on esophageal and gastric carcinogenesis might be heterogeneous, depending on subtype or subsite. However, findings from prospective evaluations of BMI associated with these cancers among Asian populations have been inconsistent and limited, especially for esophageal adenocarcinoma and gastric cardia cancer. We performed a pooled analysis of 10 population‐based cohort studies to examine this association in 394,247 Japanese individuals. We used Cox proportional hazards regression to estimate study‐specific hazard ratios (HRs) and 95% confidence intervals (CIs), then pooled these estimates to calculate summary HRs with a random effects model. During 5,750,107 person‐years of follow‐up, 1569 esophageal cancer (1038 squamous cell carcinoma and 86 adenocarcinoma) and 11,095 gastric (728 cardia and 5620 noncardia) cancer incident cases were identified. An inverse association was observed between BMI and esophageal squamous cell carcinoma (HR per 5‐kg/m2 increase 0.57, 95% CI 0.50–0.65), whereas a positive association was seen in gastric cardia cancer (HR 1.15, 95% CI 1.00–1.32). A nonsignificant and significant positive association for overweight or obese (BMI ≥25 kg/m2) relative to BMI <25 kg/m2 was observed with esophageal adenocarcinoma (HR 1.32, 95% CI 0.80–2.17) and gastric cardia cancer (HR 1.24, 95% CI 1.05–1.46), respectively. No clear association with BMI was found for gastric noncardia cancer. This prospective study—the largest in an Asian country—provides a comprehensive quantitative estimate of the association of BMI with upper gastrointestinal cancer and confirms the subtype‐ or subsite‐specific carcinogenic impact of BMI in a Japanese population. The impact of BMI on upper gastrointestinal cancer by subtype or subsite among Asians is inconclusive. Using data from 10 large‐scale population‐based cohort studies, we evaluated the association between BMI and upper gastrointestinal cancers for 394,247 Japanese individuals. With 1038 esophageal squamous cell carcinoma, 86 esophageal adenocarcinoma, 728 gastric cardia cancer, and 5620 gastric noncardia cancer cases, we confirmed the subtype‐ or subsite‐specific carcinogenic impact of BMI in an Asian population.

•This study investigated the association between Japanese diet and the intake of 12 major nutrients.•The Japanese Diet Index was preferably correlated with 11 nutrients.•This dietary pattern, however, was correlated with high sodium intake. To our knowledge, the overall nutritional quality of the Japanese diet has not been assessed previously. The aim of this study was to investigate the relationship between adhering to a Japanese diet and nutrient intake. We conducted a cross-sectional study of 1129 Japanese persons ≥70 y of age. Dietary habits were assessed using a food frequency questionnaire. The primary outcome was nutrient intake (12 components of NRF9.3 index). The overall nutrient adequacy (ONA) score was applied for assessing the potential of nutrient density. Correlation analysis was performed to compare the Japanese Diet Index (JDI) and nutrient intake, and multiple regression analysis was used to simulate the modified JDI (MJDI). The JDI was positively correlated with all nine beneficial nutrients, and negatively correlated with two nutrients (saturated fat and sugar). The JDI was significantly correlated with the ONA score (Spearman's coefficient = 0.248). The MJDI, which was defined by the coefficients for seven food items, was significantly correlated with the ONA score (Spearman's coefficient = 0.515). However, the JDI and MJDI were correlated with higher sodium intake. The present findings suggest that adhering to a Japanese diet defined by the JDI score is associated with better nutrient intake. However, this dietary pattern also appears to be associated with high sodium intake.