BackgroundEvidence on preventing Alzheimer’s disease (AD) is challenging to interpret due to varying study designs with heterogeneous endpoints and credibility. We completed a systematic review and meta-analysis of current evidence with prospective designs to propose evidence-based suggestions on AD prevention.MethodsElectronic databases and relevant websites were searched from inception to 1 March 2019. Both observational prospective studies (OPSs) and randomised controlled trials (RCTs) were included. The multivariable-adjusted effect estimates were pooled by random-effects models, with credibility assessment according to its risk of bias, inconsistency and imprecision. Levels of evidence and classes of suggestions were summarised.ResultsA total of 44 676 reports were identified, and 243 OPSs and 153 RCTs were eligible for analysis after exclusion based on pre-decided criteria, from which 104 modifiable factors and 11 interventions were included in the meta-analyses. Twenty-one suggestions are proposed based on the consolidated evidence, with Class I suggestions targeting 19 factors: 10 with Level A strong evidence (education, cognitive activity, high body mass index in latelife, hyperhomocysteinaemia, depression, stress, diabetes, head trauma, hypertension in midlife and orthostatic hypotension) and 9 with Level B weaker evidence (obesity in midlife, weight loss in late life, physical exercise, smoking, sleep, cerebrovascular disease, frailty, atrial fibrillation and vitamin C). In contrast, two interventions are not recommended: oestrogen replacement therapy (Level A2) and acetylcholinesterase inhibitors (Level B).InterpretationEvidence-based suggestions are proposed, offering clinicians and stakeholders current guidance for the prevention of AD.
Aims: To examine the association between marital status and cognitive impairment among community-dwelling Chinese older adults. Methods: We analyzed data from 2,498 Chinese aged 55 and older from the Singapore Longitudinal Aging Study cohort. Cognitive impairment was defined as a Mini-Mental State Examination total score of 23 or below. Odds ratios of associations were reported and adjusted for potential confounders in logistic regression models. Results: The prevalence of cognitive impairment was 12.2% (n = 306). Being single was associated with about 2.5 times increased odds of cognitive impairment compared to being married (adjusted OR = 2.53, 95% CI: 1.41-4.55). The association between marital status and cognitive impairment was much stronger in men compared to that in women, and was indeed statistically significant only for men. Among the single and widowed persons social engagement was associated with a lower risk of cognitive impairment. Compared with subjects in the lowest tertile of social engagement scores, the odds of having cognitive impairment was lowered by 50% for subjects in the second and the third tertile. Conclusion: Being single or widowed was associated with higher odds of cognitive impairment compared to being married in a cohort of older Chinese men but not women.
In this high-functioning elderly Chinese population, elevated homocysteine is associated with deficits in constructional ability and processing speed and folate is associated with measures of episodic memory and language. Our results provide support for differential effects of homocysteine and folate on specific cognitive functions.
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