Effects of Resveratrol Supplementation on the Cognitive Function of Patients with Alzheimer's Disease: A Systematic Review of Randomized Controlled Trials

Abstract

Background Alzheimer's disease (AD) comprises 60-70% of diagnosed dementia cases, and is characterized by the deposition of ß-amyloid peptide and the formation of neurofibrillary tangles of tau protein. Resveratrol is a neuroprotective agent acting in the prevention of redox impairment in addition to exerting anti-apoptotic actions on brain cells. An ability to reduce neuronal damage in patients with AD has been suggested by preclinical studies. Objectives The aim of this systematic review was to investigate the evidence in the published literature from studies that evaluated the effects of supplementation with resveratrol, alone or in a solution with glucose and malate (RGM), on the functional and cognitive performance of patients with AD, as assessed by validated instruments. Methods A systematic literature search was performed in MEDLINE, CENTRAL, Embase, CINAHL, Web of Science, and Scopus databases including articles published up to August 2021. Randomized, placebo-controlled, clinical trials that reported cognitive and functional performance, as measured by the Alzheimer's Disease Assessment Scale-Cognitive Subscale (ADAS-cog), Cooperative Study of Alzheimer's Disease-Activities of Daily Living (ADCS-ADL), or the Mini Mental State Examination (MMSE), in AD patients treated with resveratrol, alone or as RGM, were included. Results After 1855 studies were identified, 24 RCTs underwent full-text review, with 20 studies excluded because they did not meet the inclusion criteria. Thus, four RCTs were included in the qualitative analyses. The findings demonstrate that there are still few studies in humans, but they showed that this polyphenol acts in the delay of cognitive impairment in patients with AD, when administered alone or in combination with glucose and malate. Conclusions Supplementation with resveratrol seems to influence the progressive cognitive and functional decline in AD patients, when compared with a placebo group.