Association between tea consumption and risk of cognitive disorders: A dose-response meta-analysis of observational studies

Abstract

BackgroundThe epidemiological evidence for a dose-response relationship between tea consumption and risk of cognitive disorders is sparse. The aim of the study was to summarize the evidence for the association of tea consumption with risk of cognitive disorders and assess the dose-response relationship.MethodsWe searched electronic databases of Pubmed, Embase, and Cochrane Library (from 1965 to Jan 19, 2017) for eligible studies that published in the international journals. A random-effects model was used to pool the most adjusted odds ratios (ORs) and the corresponding 95% confidence intervals (CIs).ResultsSeventeen studies involving 48,435 participants were included in our study. The meta-analysis showed that a higher tea consumption was associated with a significant reduction in the risk of cognitive disorders (OR=0.73, 95% CI: 0.65-0.82). When considering the specific types of tea consumption, the significantly inverse association is only found in green tea consumption (OR=0.64, 95% CI: 0.53-0.77) but not in black/oolong tea consumption (OR=0.75, 95% CI: 0.55-1.01). Dose-response meta-analysis indicated that tea consumption is linearly associated with a reduced risk of cognitive disorders. An increment of 100 ml/day, 300 ml/day, and 500 ml/day of tea consumption was associated with a 6% (OR=0.94, 95% CI: 0.92-0.96), 19% (OR=0.81, 95% CI: 0.74-0.88), and 29% (OR=0.71, 95% CI: 0.62-0.82) lower risk of cognitive disorders.ConclusionsTea consumption is inversely and linearly related to the risk of cognitive disorders. More studies are needed to further confirm our findings.

Tea Consumption and Health Outcomes: Umbrella Review of Meta‐Analyses of Observational Studies in Humans

“…Tea consumption could linearly decrease the risk of cognitive disorders by 6%, 19%, 29% at 100 mL per day (0.94, 0.92–0.96), 300 mL per day (0.81, 0.74–0.88), and 500 mL per day (0.71, 0.62–0.82) . A linear association was also found between tea consumption and Parkinson's disease (PD), as the smoking‐adjusted risk of PD was lowered by 26% with two cups per day .…”

“…Tea consumption seemed to be associated with a reduced risk of cognitive disorders; dose–response analysis showed a 26% lower risk of developing PD at two cups a day (0.74, 0.61–0.89) . Recently, a double‐blind RCT conducted in individuals with Down's syndrome showed that EGCG and cognitive training for 12 months was more effective than placebo and cognitive training at improving visual recognition memory, inhibitory control, and adaptive behavior .…”

The effects of polyphenols and other bioactives on human health

“…104,105 In addition, in a meta-analysis of 17 independent observational studies, tea consumption was found to have an inverse linear relationship with the incidence of cognitive disorders. 6 Other observational studies have also shown that green and black tea consumption is related to a lower risk of experiencing cognitive impairment. 106,107 Tea consumption has further been found to independently reduce the risk for experiencing depression 108 and may have a protective effect against Parkinson's disease.…”

“…Polyphenols from various food sources such as cocoa, coffee, tea, and apples have been associated with various healthrelated benefits, including in cardiovascular disease and type 2 diabetes. [4][5][6][7][51][52][53][54][55][56][57][58][59][60][61][62][63][64] Possible mechanisms include effects on blood pressure, endothelial function, glucose metabolism, inflammation, oxidative stress biomarkers, platelet function, and cholesterol, as well as indirect effects mediated by interaction with the gut microbiome. 20,21 A portion of the evidence describing the role of polyphenols in cardiovascular health comes from epidemiologic studies involving different dietary patterns and intake of certain classes of foods.…”

“…In particular, the class of phytochemicals called polyphenols may confer health benefits, particularly as they relate to NCDs. [4][5][6][7] In contrast to vitamins and minerals and other nutrients, inadequacies in plant polyphenol intake are not associated with specific deficiency diseases, making it difficult to define appropriate reference intake values for these food components. 8 Despite this knowledge gap, many of these compounds have been identified, with some producing promising results in observational studies and randomized clinical trials in certain NCDs.…”