The relationship between tea consumption and sleep quality: A bibliometric analysis

 Corresponding author: Maya Maulida Permatasari. Copyright © 2025 Author(s) retain the copyright of this article. This article is published under the terms of the Creative Commons Attribution License 4.0. The relationship between tea consumption and sleep quality: A bibliometric analysis Maya Maulida Permatasari * Department of Industrial Engineering and Management, Faculty of Engineering, Diponegoro University, Semarang, Indonesia. World Journal of Advanced Research and Reviews, 2025, 28(02), 408-419 Publication history: Received on 20 September 2025; revised on 01 November 2025; accepted on 03 November 2025 Article DOI: https://doi.org/10.30574/wjarr.2025.28.2.3668 Abstract This study aims to analyzes the development of studies related to the relationship between tea consumption and sleep quality using a bibliometric approach based on 173 Scopus indexed documents from 2018 to 2024. Key keywords include "Sleep Quality", "Tea", "Herbal Tea", "Green Tea", and "Chamomile Tea". A bibliometric analysis with VOSviewer revealed the highest upward trend in publications in 2023 (32 documents), with the main contributions coming from the United States (13 publications, 522 citations), China (33 publications, 296 citations), and Japan (13 publications, 458 citations). Leading institutions include Ministry of Education of the People's Republic of China (5 publications) and University of Shizuoka (4 publications). Variations in research methodology were identified through the use of measurement tools such as the Pittsburgh Sleep Quality Index (PSQI), electroencephalography (EEG), and analysis of bioactive compounds (L-theanine and caffeine). The differences in that research were influenced by the type of tea (e.g. green tea vs. magnolia), the dose of consumption, and the characteristics of the participants (age, caffeine sensitivity). The results of this study suggest that tea has the potential to promote relaxation and reduce stress through neurochemical mechanisms, although the effects of caffeine need to be anticipated. The design implications of future research include the development of low-caffeine tea variants, the integration of psychometric methods (e.g., Stanford Sleepiness Scale), and a longitudinal approach to evaluating long-term impacts. Keywords: Bibliometric Analysis; Tea Consumption; Sleep Quality; VOSViewer 1. Introduction Sleep is one of the most important biological processes for humans. In addition to providing rest time for the body, sleep also plays a role in maintaining physical and mental stability, as well as maintaining overall health [1]. Sleep problems can include a variety of aspects, ranging from difficulty starting to sleep, difficulty maintaining sustainable sleep, poor sleep quality, to the habit of waking up too early [2]. This sleep disorder is a serious problem that continues to increase. For example, in the United States, the prevalence of sleep problems among working adults showed a significant increase, from 30.9% in 2010 to 35.6% in 2018 [3]. This condition shows that sleep disorders are not only an individual problem but also a public health issue. Although certain medications have been shown to be effective in treating severe cases of insomnia, many individuals are still looking for safe, effective, and easily accessible alternative solutions to improve their sleep quality [4]. One potential solution that is increasingly attracting attention is the use of functional foods. These foods contain bioactive compounds that can provide additional health benefits, including helping to improve sleep quality [4], [5]. Several types of functional foods have been proposed as potential sleep aids. One of the most popular is tea. Drinking tea is a very common habit, especially in Asian countries [6]. Tea derived from the leaves of the Camellia sinensis plant contains a variety of active biomolecules, such as flavonoids and antioxidants, which are known to have biological properties, including warding off free radicals and providing protection against oxidative stress [7]. Based on the World Journal of Advanced Research and Reviews, 2025, 28(02), 408-419 409 processing method, tea can be categorized into three main types: black tea, green tea, and oolong tea. Of the total tea produced globally, as much as 78% is black tea, which is widely consumed in Western countries, 20% is green tea, which is popular in Asian countries, and only about 2% is oolong tea, which is produced by partial fermentation, especially in the South China region [8], [9], [10]. Each type of tea has different characteristics and bioactive content, so its effects on health, including sleep quality, can also vary. Although research on the relationship between tea consumption and sleep quality continues to grow, the available results still show uncertainty due to differences in methodology, type of tea consumed, participant characteristics, and intervention approaches used. Some studies suggest that tea may exert positive effects on sleep through neurochemical mechanisms, such as L-theanine's role in promoting relaxation, while inhibitory factors such as caffeine content are still a challenge. To further understand the impact of tea consumption on sleep quality, this study combines a bibliometric analysis based on VOSviewer and a systematic literature review (SLR) of 173 Scopus indexed documents from 2018 to 2024 which will be used as some of the research questions: 1. Analyze the relationship between keyword occurrence and citation patterns using VOSviewer? 2. Map the development of research related to tea consumption and sleep quality based on publication trends, country/institution contributions, and author collaboration? 3. Evaluate the impact of tea consumption on sleep quality by considering the variables of tea type, dosage, and participant profile? and 4. Identify research gaps, such as the need for longitudinal studies and the development of low-caffeine tea variants, to support innovation of non-pharmacological interventions 2. Methods 2.1. Search Strategy The data search strategy for this study was carried out by utilizing the Scopus search engine. In this study, literature related to tea consumption and sleep quality was obtained through a search in Scopus using the following keywords: "Sleep quality" AND "tea" OR "herbal tea" OR "green tea" OR "chamomile tea" OR "magnolia tea." The search period is set from January 2014 to December 2024, with additional criteria in the form of an English-only article language. The type of literature selected is limited to scientific articles and reviews. In addition, articles that explicitly discuss the link between caffeine and sleep quality are also manually filtered to ensure only studies relevant to the research topic are included-search details in figure 1. Figure 1 Article Selection Process Diagram World Journal of Advanced Research and Reviews, 2025, 28(02), 408-419 410 2.2. Data Collection After the literature is obtained through a search in Scopus, the documents are exported in CSV format with the recording content settings including full record and cited references. This process allows for a comprehensive bibliometric analysis of the collected literature. The data obtained were then summarized based on various parameters such as authors, institutions, countries, journals, and citation frequency to identify patterns and trends in research related to tea consumption and sleep quality. To support bibliometric analysis, VOSviewer software is used. VOSviewer is a bibliometric analysis tool designed to visualize and analyze scientific literature networks. The software automatically processes bibliographic data, identifies relevant keywords, calculates the frequency of keyword occurrences, and performs co-occurrence or co-occurrence analysis of keywords. Based on the relationships between keywords, the algorithm in VOSviewer generates clustering that allows researchers to explore patterns, relationships, and key insights in the literature network. In addition to bibliometric analysis, systematic reviews are also conducted. Researchers manually excluded duplicate articles based on title and abstract. Then, studies that meet the criteria are selected and analyzed in depth. The data obtained from the selected study is recorded in a table using Microsoft Excel. The extracted information includes the author's name, year of publication, country of origin of the study, characteristics of participants (such as number and age), study design, type of tea used, measurements as well as results. 2.3. Data Extraction From each of selected studies, the following information was extracted in detail: • Research objectives • Country of origin of the study • Participant characteristics, including sample size and age • The study design used • Sleep quality measurement method • The main results obtained All data is recorded and organized using Microsoft Excel to ensure accuracy and ease of access during analysis. This approach allows researchers to evaluate patterns, trends, as well as relevant relationships between tea consumption and sleep quality in a systematic and structured manner. 3. Results and discussion This section provides a comprehensive presentation of the results of bibliometric analysis. The main purpose of this analysis is to present a summary of the research on the relationship between tea consumption and sleep quality 3.1. Publication by Year As seen in Figure 2, research on the relationship between tea consumption and sleep quality has improved significantly in the last decade, specifically from 2014 to 2024. The initial number of publications was relatively low, with only a few articles published between 2014 and 2016. In 2017, there were nine publications, and this number began to increase gradually. In 2020, there was a significant surge with 21 publications, which lasted until 2021. This trend further strengthened in 2022 with 28 publications, followed by rapid growth in 2023 (33 publications) and peaked in 2024 with 38 publications. Overall, publications in the last three years (2022-2024) accounted for about 57% of the total research analyzed. This increase in the number of studies indicates a growing academic interest in the topic of tea consumption and sleep quality, which is likely driven by increasing awareness of the importance of sleep health as well as the exploration of non-pharmacological interventions to improve sleep quality. These figures clearly reflect the growing research trends in this area and confirm the relevance and urgency of further study in this domain. World Journal of Advanced Research and Reviews, 2025, 28(02), 408-419 411 Figure 2 Research Trends Publication from 2014 to 2024 3.2. Publications by Author A total of 160 authors has contributed to this field. Table 1 presents the top 10 most prolific authors, each with 2–4 publications. The authors with the highest contributions are Iguchi, K; Morita, A; Nakamura, Y; Unno, K; and Yamada, H., each with a total of 4 publications. The co-authorship analysis shown in Figure 3 shows that there is a wide network of collaboration among the authors. The network reflects cross-disciplinary and institutional collaborations that allow for the exchange of ideas as well as the development of new approaches in research. This strong collaboration is important in answering the complexities of problems related to sleep quality and tea consumption, as well as promoting innovation in this area. Table 1 Top authors by number of publications Author Publication Iguchi, K. 4 Morita, A. 4 Nakamura, Y. 4 Unno, K. 4 Yamada, H. 4 Ao, L. 2 Baba, Y. 2 Cao, J. 2 Chen, Q. 2 Dualé, C. 2 Source: Scopus, 2024 World Journal of Advanced Research and Reviews, 2025, 28(02), 408-419 412 Figure 3 Analysis of Co-authorship of authors 3.3. Publications by Institution A total of 158 institutions has published literature related to tea consumption and sleep quality. Ministry of Education of the People's Republic of China became the institution with the most publications, namely 5 publications, followed by the University of Shizuoka with 4 publications. Table 2 presents a list of the top 10 institutions by number of publications. The institutional dominance of China and Japan reflects the great attention of Asian countries to the potential benefits of tea in improving health, including sleep quality. The large number of institutions contributing shows that this topic is relevant in various research contexts and has global appeal. Table 2 Top 10 institutions by number of publications Institutions Publication Ministry of education of the people’s republic of China 5 University of Shizuoka 4 Inserm 3 Nanjing University of Chinese Medicine 3 Chengdu University of Traditional Chinese Medicine 2 Jilin University 2 Universidade de Sao Paulo 2 China Medical University Shenyang 2 Sanofi S.A 2 Pukyong National University 2 Source: Scopus, 2024 3.4. Publications by Country The analysis by country shows that China has the highest number of publications, at 33 publications with 296 citations, followed by the United States (13 publications, 522 citations) and Japan (13 publications, 458 citations). Table 3 summarizes the 10 countries with the highest publications. Figure 4 shows a visualization map of co-authorship by country, showing the close relationship between researchers from different countries. China's dominance in the number of publications shows the country's important position in tea-related research, which is also supported by a strong tradition of tea consumption in its society. World Journal of Advanced Research and Reviews, 2025, 28(02), 408-419 413 Table 3 Top 10 Countries by number of publications Country Publication Citation Total link strength China 33 296 6 Japan 13 458 3 United States 13 522 13 South Korea 9 216 2 United Kingdom 7 283 11 Brazil 6 119 10 Iran 5 47 4 Italy 5 231 0 France 4 347 2 India 4 65 1 Source: Scopus, 2024 Figure 4 Co-authorship Analysis by Country 3.5. Publication Based on Journal Publishing The documents included in this study come from 75 journals. The journal Nutrients was the most prolific with 13 publications and 494 citations, followed by Frontiers in Nutrition and Heliyon, with 4 publications each. Table 4 presents a list of the 10 journals with the highest number of publications. Nutrients' dominance as a top journal demonstrates the high relevance of this topic to the field of nutrition, which highlights the potential of tea as a healthsupporting functional food. Table 4 Top 10 Journal by number of publications Journal Publication Citations Total link strength Nutrients 13 494 3 Frontiers In Nutrition 4 31 0 Heliyon 4 24 1 Frontiers In Medicine 2 31 1 International Journal of Molecular Sciences 2 16 0 Journal of Medicinal Food 2 30 1 Journal of Nutrition Health and Aging 2 16 0 Journal of Sleep Research 2 22 0 World Journal of Advanced Research and Reviews, 2025, 28(02), 408-419 414 Nutritional Neuroscience 2 31 0 Plos One 2 13 0 Source: Scopus, 2024 3.6. Publication Based on Number of Citations List of the 10 most frequently cited publications. The most frequently cited article is published in Frontiers in Psychiatry with a total of 325 citations by Temple et al. In this review article provides an overview of caffeine consumption, which is the most widely consumed psychoactive drug in the world. This article covers a wide range of topics related to caffeine, including natural and synthetic sources of caffeine, consumption patterns in different populations, as well as the health effects of caffeine consumption on healthy individuals and vulnerable groups such as pregnant women, children, and people with certain health conditions. This article highlights some of the challenges faced in research on caffeine, including the lack of consensus regarding safe doses for different population groups and the need to better understand the long-term effects of caffeine consumption, especially in more vulnerable groups. Additionally, this article emphasizes the need for further research to understand the mechanism of action of caffeine, genetic variation in caffeine metabolism, as well as its impact on mental and physical health. Additional research is also needed to explore how factors such as age, gender, and health conditions affect the effects of caffeine. Table 5. The following is a list of the 10 most cited journal publications. Table 5 Top 10 Publications with the highest number of citations Title Journal Citation Year The Safety of Ingested Caffeine: A Comprehensive Review Frontiers in Psychiatry 325 2017 Nutrition, physical activity, and other lifestyle factors in the prevention of cognitive decline and dementia Nutrients 175 2021 Effects of Oral Gamma-Aminobutyric Acid (GABA) Administration on Stress and Sleep in Humans: A Systematic Review Frontiers in Neuroscience 152 2020 GABA and L-theanine mixture decreases sleep latency and improves NREM sleep Pharmaceutical Biology 106 2019 Effects of an intervention with drinking camomile tea on sleep quality and depression in sleep disturbed postnatal women: A randomized controlled trial Journal of Advanced Nursing 76 2016 Effect of caffeine consumption on the risk for neurological and psychiatric disorders nutrients 66 2020 Stress-reducing function of matcha green tea in animal experiments and clinical trials Nutrients 62 2018 Effects of chronic L-theanine administration in patients with major depressive disorder Acta Neuropsychiatrica 62 2017 Pain-relieving agents for infantile colic Cochrane Database of Systematic Reviews 51 2016 Dietary polyphenols targeting arterial stiffness: Interplay of contributing mechanisms and gut microbiome-related metabolism Nutrients 46 2019 Source: Scopus, 2024 3.7. Analysis Co-Occurrence Based on Keywords A network visualization map of all keywords is illustrated in Figure 5. Different colors represent different directions of research focus. The dot size reflects the frequency with which keywords appear. All the keywords form 5 groups such as: World Journal of Advanced Research and Reviews, 2025, 28(02), 408-419 415 • Red Clusters are sleep, sleep, sleep time, sleep latency, sleep efficiency, sleep pattern, sleep disorders, sleep deprivation, rem sleep, drug effect, caffeine, stress, and green tea. • Yellow Clusters are female, male, middle age, aging, risk factor, demography, health status, hypertension, and diabetes melitus. • Green Clusters are Human, sleep quality, tea, insomnia, anxiety, depression, sleep wake disorders, melatonin, fatigur, antioxidant, and aromatheraphy. • Blue Clusters are adult, young adult, coffee, body mass, exercise, physical activity, drinking behavior, energy drink, soft drink, alcohol, beverage, milk, fruit and vegetable. • Purple Clusters are Pittsburgh Sleep Quality Index, tea consumption, coffee consumption, smooking, age, gender, and marriage. Figure 5 Visualization of co-occurrence analysis by keywords 3.8. Literature Review As a result of the systematic review analysis, as many as 11 journals relevant to this research topic were included in the final evaluation. The journals were selected based on strict selection criteria and included important information such as research objectives, geographical location, participant characteristics, study design, measurement methods, and research results (Table 6). A thorough analysis of these journals aimed to deeply understand the relationship between tea consumption and sleep quality and how various factors affect these outcomes. This study was conducted to summarize the methodology and results of previous studies to determine a clear relationship between tea consumption and sleep quality. The eleven selected studies showed variations in terms of geographical location (e.g., China, Japan, Korea, France), the type of tea used (such as green tea, magnolia tea, and herbal tea containing Hibiscus syriacus L or L-theanine), the design of the study (including randomized controlled trials), and the characteristics of participants (adolescents, adults, to the elderly). Various positive results found include a decrease in stress levels, depression, pain, and fatigue that contribute to improved sleep quality. However, it is important to remember that the interpretation of these results requires caution, given the variation in age, health conditions, and research methodology across the studies analyzed. Some studies show that the consumption of tea at night has a significant positive effect on sleep quality due to the specific bioactive content, such as L-theanine in green tea, which has natural relaxing properties. In addition, randomized controlled studies (RCS) involving herbal tea products containing Hibiscus syriacus L, magnolia tea, and green tea showed that tea can help improve sleep efficiency, reduce insomnia, and improve the overall sleep experience World Journal of Advanced Research and Reviews, 2025, 28(02), 408-419 416 Table 6 Top 10 Publications with the highest number of citations Ref Objective Country Participants Measurement Result [11] The relationship between tea habits and quality of life and the mediating effect of sleep quality China 300.000 permanents residents ≥ 18 years old (adults) HRQoL was measured using a 12-item Short-Form Health Survey. Maintaining the habit of drinking tea (6-7 days per week), in small amounts (<10 g of tea per day) is conducive to increasing the HRQoL of Chinese adults by improving sleep quality. [12] Effect of matcha green tea on cognitive function and sleep quality Japan 124 participants aged 60-85 years (Older adults) Montreal Cognitive Assessment, Alzheimer’s Disease Cooperative Study Activity, PSQI. The study showed regular consumption of matcha may improve emotional perception and sleep quality in older adults with mild cognitive decline. [13] Effect of Tea Consumption on Cognitive Function and Examining Possible Psychosocial Mechanisms with Sleep Quality China 11,910 participants aged ≥ 60 years (Older adults) Propensity Score Matching (PSM) Frequent consumption of tea was found to have a beneficial effect on cognitive function, especially in older people with green tea intake. Sleep quality and depression levels partly mediate the relationship between frequent tea consumption and cognitive function among older Chinese adults. [14] Effect of Hibiscus syriacus L. flower extract (used for tea) on sleep quality Korea 80 participants aged 19 to 65 years old (Adults) PSQI, Insomnia Severity Index (ISI), Epworth Sleep Scale (ESS), sleep diary, and polysomnography (PSG) The potential of HSF extract as a functional food that improves sleep quality in humans will be evaluated, and the trial findings will be submitted to the Korean Ministry of Food and Drug Safety for consideration as a new functional ingredient that can help improve sleep quality. [15] Effect of the combination of magnesium, vitamins B6, B9, B12, rhodiola and green tea/L-theanine (MgTeadiola) on stress-related quality of life parameters (sleep and pain perception). France 123 participants aged 18 to 65 years (Adults) PSQI, Depression Anxiety Stress Scale (DASS) Mg-Teadiola was effective in relieving stress on Days 14 and 28 in chronically stressed but healthy individuals. These findings, in addition to the observation that Mg-Teadiola can reduce pain perception, underscore its potential benefits for patients suffering from pain, where comorbidities such as stress and sleep disturbances are common. Ref Objective Country Participants Measurement Result [16] Three components of herbal tea reduce prolonged fatigue and improve sleep quality Korea 40 participants aged 35 to 44 years (adults) Chalder Fatigue Scale In this study, herbal tea treatment improved sleep quality, in a pattern similar to that observed for fatigue improvement. These results highlight the potential usefulness of herbal teas for treating sleep disorders that accompany fatigue.