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Background: Sleep is a potentially modifiable factor associated with dementia, including Alzheimer's disease, but current evidence supporting this is insufficient. Objective: This study aimed to determine whether sleep duration and bedtime patterns are associated with the risk of dementia among middle-aged and older people. Methods: This cohort study had an eight-year follow-up period. Participants were 13,601 community-dwelling people aged 40–74 years living in Murakami (Niigata, Japan). Data were collected using a self-administered questionnaire. Predictors were self-reported sleep duration and bedtime, and the outcome was newly-diagnosed dementia determined using the long-term care insurance database. Covariates were demographic characteristics, body mass index, smoking, alcohol consumption, total physical activity, insomnia symptoms, disease history, and either bedtime or sleep duration. Cox proportional hazard models were used to calculate hazard ratios (HRs). Results: The mean age of participants at baseline was 59.2 years. Over a mean follow-up period of 8.0 years, 319 cases of dementia were observed. A long self-reported sleep duration relative to the reference sleep duration (7 hours) was associated with increased dementia risk, with the "8 hours" group (adjusted HR = 1.30, 95% CI:0.99–1.73) and "≥9 hours" group (adjusted HR = 1.46, 95% CI:1.00–2.15) having an increased risk (marginally significant) relative to the reference group. Early bedtime was associated with increased dementia risk (adjusted p for trend = 0.0010), with the "21 : 00 or earlier" group (adjusted HR = 1.61, 95% CI:1.14–2.28) having an increased risk relative to the reference ("23 : 00"). Conclusions: A long self-reported sleep duration and early bedtime are both associated with increased dementia risk in middle-aged and older people [ABSTRACT FROM AUTHOR]

Background: The association between body mass index (BMI) and dementia risk is heterogeneous across age groups and might be influenced by sex. Objective: This study aimed to clarify sex differences in the association between BMI and dementia risk in community-dwelling people. Methods: This cohort study with an 8-year follow-up targeted 13,802 participants aged 40–74 years at baseline in 2011–2013. A self-administered questionnaire requested information on body size, including height, weight, and waist circumference (the values of which were validated by direct measurement), socio-demographics, lifestyle, and disease history. BMI was calculated and categorized as < 18.5 (underweight), 18.5–20.6 (low-normal), 20.7–22.6 (mid-normal), 22.7–24.9 (high-normal), 25.0–29.9 (overweight), and≥30.0 kg/m2 (obese). Incident cases of dementia were obtained from the long-term care insurance database. A Cox proportional hazards model was used to calculate multivariable-adjusted hazard ratios (HRs). Results: The mean age of participants was 59.0 years. In men, higher BMI was associated with lower dementia risk (fully-adjusted p for trend = 0.0086). In women, the association between BMI and dementia risk was U-shaped; the "underweight," "low-normal," and "overweight" groups had a significantly higher risk (fully-adjusted HR = 2.12, 2.08, and 1.78, respectively) than the reference ("high-normal" group). These findings did not change after excluding dementia cases which occurred within the first four years of the follow-up period. Conclusion: Overweight/obese women, but not men, had an increased risk of dementia, suggesting that sex differences in adiposity might be involved in the development of dementia. [ABSTRACT FROM AUTHOR]

Objectives Coffee, green tea, and caffeine are potential preventive factors for dementia, but the underlying evidence is insufficient. This study aimed to examine associations between the consumption of coffee, green tea, and caffeine and dementia risk in middle‐aged and older people. Methods: This was a cohort study with an 8.0‐year follow‐up. Participants were community‐dwelling individuals (n = 13,757) aged 40–74 years. A self‐administered questionnaire survey was conducted in 2011–2013. Predictors were the consumption of coffee/green tea, from which caffeine consumption was estimated. The outcome was incident dementia obtained from the long‐term care insurance database. Covariates were demographic factors, body mass index, physical activity, energy, smoking, drinking, and disease history. Adjusted hazard ratios (HRs) were calculated using Cox proportional hazards models. HRs were also calculated using a Cox model with delayed entry. Results: The number of dementia cases during the study period was 309. Participants with higher coffee consumption had lower HRs (adjusted p for trend = 0.0014), with the fifth quintile (≥326 ml/day) having a significantly lower HR (0.49, 95% confidence interval [CI]: 0.30–0.79) than the first quintile (<26 ml/day, reference). Similarly, participants with higher caffeine consumption had a significantly lower HR (adjusted p for trend = 0.0004) than the reference. The Cox model with delayed entry yielded similar results. These associations were significant in men, but not in women. Moreover, participants who consumed 2–2.9 cups/day and ≥3 cups/day of coffee had lower HRs (0.69, 95% CI: 0.48–0.98 and 0.53, 95% CI: 0.31–0.89, respectively) than those who consumed 0 cup/day. The association between green tea consumption and reduced dementia risk was significant (adjusted p for trend = 0.0146) only in the 60–69 years age subgroup. Conclusions: High levels of coffee and caffeine consumption were significantly associated with a reduced dementia risk in a dose‐dependent manner, especially in men. Moreover, coffee consumption of ≥3 cups/day was associated with a 50% reduction in dementia risk. [ABSTRACT FROM AUTHOR]

Objective: In this 5‐year cohort study, we aimed to determine whether the intake of natto, a fermented soya bean food product, has an indirect effect on tooth loss incidence through BMD changes among postmenopausal women. Background: Evidence indicates (1) that natto has a beneficial effect on bone health and (2) that a decrease in bone mineral density (BMD) is associated with tooth loss. Methods: The study recruited 435 postmenopausal women (average age = 64.2 years). Natto intake (exposure) was assessed at baseline using a food frequency questionnaire. Lumbar spine BMD and number of teeth were measured at baseline and 5‐year follow‐up. BMD change (mediator) and the number of teeth lost (outcome) over time were calculated. The mediation model consisted of these 3 variables. Mediation analysis was performed to test the indirect effect of the natto intake measured through BMD change on tooth loss. Results: During the study, the mean number of teeth lost was 1.2 (standard deviation = 1.8), and the mean BMD decline was 2.5% (standard deviation = 7.1). After adjusting for potential confounders, increasing habitual natto intake was significantly indirectly associated with a lower incidence of tooth loss mediated by BMD change (incidence rate ratio of tooth loss among women with "≥1 pack/day" natto intake was 0.90 [95% confidence interval = 0.82‐0.99] compared to those with natto consumption of "rarely"). Conclusions: Dietary natto intake is significantly indirectly associated with a lower incidence of tooth loss among postmenopausal women, and systemic bone density could be a mediator of this association. [ABSTRACT FROM AUTHOR]

Aims: A prior meta‐analysis found that obesity (body mass index [BMI] ≥ 30 kg/m2) was associated with a high fall risk, while being overweight (BMI≥25, <30 kg/m2) was associated with the lowest fall risk. However, whether these associations hold true for East Asians is unknown. This study aimed to assess the association between BMI and incidence of recurrent falls in Japanese aged 40–74 years. Methods: This 5‐year follow‐up cohort study involved 7538 community‐dwelling individuals who did not experience recurrent falls in the year before the baseline study. Information on demographics, body size, lifestyle, and disease history was obtained using a self‐administered questionnaire. BMI was categorized as <18.5 (underweight), 18.5–20.6 (low‐normal), 20.7–22.7 (mid‐normal, reference), 22.8–24.9 (high‐normal), and ≥ 25.0 kg/m2 (overweight). The outcome was recurrent falls reported, and fall history in the previous year was recorded as none, once, or twice or more (recurrent falls). Results: Mean BMI was 23.5 kg/m2 (SD 2.9) for men and 22.7 kg/m2 (SD 3.2) for women. The adjusted odds ratio (OR) for recurrent falls in the BMI ≥25 group was significantly higher (1.41, 95%CI: 1.02–1.93) than that in the reference group. The adjusted OR in the BMI ≥25 group was significantly higher than that in the reference group for the age ≥ 60 subgroup (1.62, 95%CI: 1.09–2.40), but not for the age < 60 subgroup (OR = 1.04, 95%CI: 0.60–1.80). Conclusions: Being overweight may be a risk factor for recurrent falls in community‐dwelling older Japanese. Further studies are needed to determine the underlying mechanism. Geriatr Gerontol Int 2021; 21: 498–505. [ABSTRACT FROM AUTHOR]