Background: It is unclear whether overweight and obesity in older age reduces or increases the risk of incident dementia. Objective: To assess the impacts of overweight and obesity in older age on incident dementia. Methods: We searched cohort studies reporting body weight measured in older age and dementia through PubMed, Embase, Medline, PyschInfo, and Cochrane library until July 2016. Sixteen articles were identified for the review. We pooled data from them and a new unpublished study from China, to calculate relative risk (RR) of incident dementia in relation to body mass index (BMI) and waist circumference (WC). Results: All 16 cohort studies were undertaken in high income countries, with follow-up periods ranging between 3 to 18 years. Thirteen studies showed an inverse association between BMI and dementia, and three studies demonstrated a positive association. Pooled RR of dementia in relation to continuous BMI from 14 studied populations, including the new Chinese data, was 0.97 (95% CI 0.95–1.00); in those followed up <9 years it was 0.95 (0.93–0.96) while in ≥9 years follow-up it was 1.03 (0.96–1.11). In five studied populations examining categorical BMI, RR of dementia in older people classified as overweight and obese was 0.98 (0.54–1.77) and 1.17 (0.65–2.10) respectively, in comparison with other weights. The pooled WC data showed no association between increased WC and reduced risk of dementia. Conclusion: The current evidence did not support a paradox on beneficial impacts of overweight and obesity in older age on incident dementia. More studies with long term follow up are needed to clarify the association of body weight in older age with dementia risk.

Objective: Periodontal disease (PD) is common and increases cardiovascular diseases. However, it is unclear whether PD is associated with increased risk of dementia. We carried out a systematic review and meta-analysis to investigate the influence of PD on dementia. We projected the number of dementia cases to be saved by reducing PD prevalence in the world. Method:We searched cohort and case-control studies reporting the association of PD with all dementia (or any specific type of dementia) through PubMed, MEDLINE, PsycINFO, SocINDEX, CINHAL, and CNKI until 7 th November 2018. Five cohorts and seven casecontrol studies were identified for review. We pooled eligible data to calculate relative risk (RR) of dementia in relation to PD and computed the number of dementia cases saved through reducing PD prevalence.Results: Of 12 studies, six were undertaken in Asia, four in Europe and two in America.Eleven studies showed a positive association between PD and the risk of dementia, of which 10 were significant, and one reported a non-significant inverse association. Overall their quality was good. Pooled RR of dementia in relation to PD from all high quality studies was 1.38 (95%CI 1.01-1.90); in the five cohorts was 1.18 (1.06-1.31) and in the two case-control studies 2. 25 (1.48-3.42). A 50% reduction in the current prevalence of 20% of PD in the population could save 850,000 (630,000-1,420,000) patients with dementia in the world.Conclusions: PD could increase the risk of incident dementia. Preventing and treating PD could contribute to controlling the global epidemic of dementia.

Greater consumption of fish is associated with a lower risk of dementia. Increasing fish consumption may help prevent dementia worldwide regardless of income level.

Background Increased fish consumption reduces the risk of dementia. However, it is unknown whether fish consumption reduced all-cause mortality in people with dementia. The purpose of the study is to investigate the association of fish consumption with all-cause mortality in older people with dementia versus those without dementia. Methods Using a standard method of the Geriatric Mental State, we interviewed 4165 participants aged ≥ 60 years who were randomly recruited from five provinces in China during 2007–2009 to collect the baseline data of socio-demography, disease risk factors, histories of disease, and details of dietary intakes, and diagnosed dementia (n = 406). They were followed up for vital status until 2012. Results The cohort follow-up documented 329 deaths; 61 were in participants with dementia (55.3 per 1000 person-years) and 224 were those without dementia (22.3). In all participants, the risk of all-cause mortality was reduced with fish intake at “ ≥ twice a week” (multivariate-adjusted hazard ratio 0.58, 95% CI 0.34–0.96) and at “once a week or less” (0.79, 0.53–1.18) compared to “never eat” over the past two years. In participants without baseline dementia, the corresponding HRs for all-cause mortality were 0.57 (0.33–0.98) and 0.85 (0.55–1.31), while in participants with dementia were 1.36 (0.28–6.60) and 1.05 (0.30–3.66), respectively. Conclusion This study reveals that consumption of fish in older age reduced all-cause mortality in older people without dementia, but not in people with dementia. Fish intake should be increased in older people in general, prior to the development of dementia in the hope of preventing dementia and prolonging life.

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