Study: Effect of matcha green tea on cognitive functions and sleep quality in older adults with cognitive decline: a randomized controlled trial for 12 months. Image credits: masa44 / Shutterstock
Daily matcha intake sharpens social cognition and improves sleep quality, offering potential benefits for older adults dealing with early stages of cognitive decline.
A randomized, controlled clinical trial was recently conducted to investigate the effect of matcha green tea intake on cognitive function and sleep quality in individuals with mild cognitive impairment. The pilot report is published in the journal PLOS ONE.
Background
Dementia is one of the most serious age-related neurodegenerative diseases worldwide. According to the World Alzheimer Report 2022, the number of dementia patients is expected to rise from 57 million in 2019 to 152 million in 2050.
Sleep disturbance is another major problem in the aging population. Reducing sleep duration from 7 hours to 6 hours has been found to increase the risk of dementia by 30% in older adults between the ages of 50 and 60.
Lifestyle habits, including diet, play a crucial role in maintaining cognitive functions in older adults. Preclinical studies have reported that nutrition is essential in preventing dementia-related cognitive decline.
Matcha green tea powder contains several bioactive compounds, including epigallocatechin gallate (EGCG), theanine and caffeine, which are known to have a beneficial effect on cognitive functions and mood.
In this randomized controlled clinical trial, scientists examined the effect of matcha green tea on cognitive function and sleep quality in older adults living in Japan over a 12-month period.
Study design
A total of 99 older adults aged 60 – 85 years took part in the trial. Of these, 64 had subjective cognitive decline, and 35 had mild cognitive impairment.
The participants were randomly divided into two groups: the intervention group and the control group. The intervention group received two grams of matcha green tea daily for twelve months. The control group participants received placebo capsules that were identical to the matcha capsules in appearance, color and smell.
Participants’ cognitive functions and sleep quality were measured at baseline and at 3-, 6-, 9-, and 12-month follow-up visits.
Important observations
The study found that intake of matcha and placebo capsules was 98-99% throughout the study period. A significantly increased blood theanine level in the matcha group compared to that in the placebo group also indicated high compliance with the study intervention.
The evaluation of the perception of facial expressions in cognitive functions indicated that the intake of matcha green tea is associated with a significant increase in social cognition, including recognition of facial expressions and descriptions (word meanings). However, it is important to note that no significant improvements were observed in the primary cognitive outcomes, including Montreal Cognitive Assessment (MoCA-J) and Alzheimer’s Disease Cooperative Study Activity of Daily Living (ADCS-MCI-ADL) scores. An improving trend in sleep quality was also observed in participants who consumed matcha green tea for 12 months.
However, no significant differences were observed between the matcha and placebo groups in other cognitive functions tested, including functional skills in daily life, attention and concentration, executive functions, memory, language, visuoconstructive skills, conceptual thinking, calculations and orientation.
In facial expression perception tests, a reduction in false responses and a shortening of simple reaction time were observed in matcha-consuming participants compared to placebo-consuming participants.
The study found that there were significant positive correlations between social cognition scores and cognitive impairment in all participants at the baseline and 12-month visits. The correlations were stronger in participants with subjective cognitive decline than in participants with mild cognitive impairment.
Significant correlations were also observed between social cognition scores and conventional cognitive functioning test scores in participants with subjective cognitive impairment, but not in participants with mild cognitive impairment.
Study meaning
The study findings indicate that regular consumption of matcha green tea can improve emotional perception and sleep quality in older adults with subjective cognitive decline or mild cognitive impairment. However, the absence of significant changes in primary cognitive outcomes suggests that the benefits of matcha may be limited to specific aspects of cognition, such as social acuity, rather than broader cognitive functions.
The sleep quality-improving effect of matcha green tea can be attributed to its theanine content. Previous studies involving both healthy adults and schizophrenia patients have shown that theanine intake is associated with better sleep quality.
A large body of evidence has suggested that sleep disorders can significantly increase the risk of developing mild cognitive impairment. Improving sleep quality by continuous positive airway pressure therapy, together with administration of donepezil, has been shown to improve cognitive performance in patients with mild cognitive impairment.
Given these observations, the current study suggests that matcha-mediated improvement in sleep quality could be responsible for the observed improvement in social cognition in the intervention group.
However, the study findings should be interpreted with caution due to certain limitations. A major limitation is the relatively small sample size, which may not fully represent the broader population of older adults with cognitive decline. Additionally, the study relied on self-reported measures of sleep quality, such as the Pittsburgh Sleep Quality Index (PSQI), which may not capture all aspects of sleep architecture. More objective measures, such as polysomnography, are recommended in future studies to assess sleep stages, including REM and non-REM sleep.
The cultivation method of Matcha green tea differs from conventional green tea. This alternative cultivation method increases the levels of catechins and theanine, making matcha green tea potentially superior to green tea in terms of health benefits.
Matcha green tea is widely available and culturally well accepted worldwide. Thus, incorporating it into the daily routine can provide a simple yet effective strategy for cognitive enhancement, improving sleep quality and preventing dementia.
Future studies are needed to comprehensively investigate the long-term effects of matcha on cognitive decline. These studies should include larger sample sizes, more sensitive neuropsychological tests, and biomarker analyzes to better understand the mechanisms underlying matcha’s effects on cognition and sleep.
Furthermore, it would be useful to investigate whether the observed improvements in social cognition translate into meaningful changes in daily functioning and quality of life in older adults at risk for dementia.