Introduction

According to the latest World Health Organization statistics, approximately 13.7 million deaths in 2016 were attributable to modifiable environmental risk factors, representing 24% of global mortality and highlighting the substantial impact of environmental conditions on human health. A wide range of environmental hazards—including air, water, and soil pollution, climate degradation, ultraviolet radiation, and noise—have been implicated in the onset of over 100 diseases and injuries, such as dyspepsia, mental disorders, chronic bronchitis, cardiovascular and cerebrovascular diseases, and various forms of cancer1,2,3,4,5,6,7. Chronic conditions such as hypertension, diabetes, coronary heart disease, and stroke pose significant threats to the health of middle-aged and elderly populations, severely diminishing quality of life and placing considerable strain on public healthcare systems8,9,10,11.

The natural environment serves as the foundation for forest therapy, with its air, water, and vegetation constituting integral therapeutic elements. In the 1990s, Japanese researchers first recognized the medical potential of natural environments and introduced the concept of “forest bathing”12,13,14. A growing body of evidence has since validated the physiological and psychological benefits of forest therapy, including reductions in blood pressure and heart rate, alleviation of stress, improvements in depressive and anxiety symptoms, attenuation of sympathetic nervous system activity, enhancement of parasympathetic function, and modulation of autonomic nervous system balance15,16,17,18,19,20,21,22,23. Short-term exposure to forest environments has also been associated with elevated activity and counts of natural killer (NK) cells24,25. A positive association exists between forest exposure and mental health, with such environments shown to reduce negative emotions and enhance psychological resilience26,27. Salivary cortisol levels—a biomarker of stress—are closely linked to sleep quality, with evidence suggesting that forest settings improve sleep, alleviate psychological distress, and contribute positively to the physical and mental well-being of individuals with depression or other psychiatric disorders28,29,30,31. Marycolo et al. proposed the “20-minute park effect,” demonstrating that even brief exposure (20–30 min) to natural settings significantly reduces stress levels32. Nature contact has also been shown to buffer the adverse effects of stress on both mental and physical health33,34,35,36,37. At the physiological level, short-term forest therapy leads to marked decreases in systolic blood pressure (SBP) and diastolic blood pressure (DBP), as well as heart rate, alongside increases in NK cell activity and counts38. Additionally, elevated concentrations of negative air ions (NAIs) in natural environments have been shown to enhance antioxidant capacity, combat fatigue, regulate the nervous system, and offer supportive effects in disease management39,40.

Existing literature extensively documents the health benefits of natural environments; however, limited research addresses the physiological impacts of specific ecological settings. Tea forests, known for their roles in carbon sequestration, oxygen release, climate regulation, and ecological enhancement, remain underexplored as therapeutic environments. Current studies primarily emphasize the health-promoting properties of tea consumption, which constitutes a lifestyle intervention, whereas exposure to tea groves represents an environmental stimulus—two fundamentally distinct pathways influencing human health. It is hypothesized that the unique volatile organic compounds (VOCs) emitted by tea forests may exert beneficial effects on metabolic function, immune regulation, respiratory health, and psychological well-being, including stress and anxiety reduction. According to data from the Tea Industry Special Task Force of Guizhou Province, China, the region’s tea forest area reached 466,666.67 hectares in 202241, with Fenggang County ranked as the second-largest tea-producing region in the province and recognized nationally as a key production base42. The present study employed a controlled design to evaluate the physiological and psychological benefits of short-term tea forest exposure—through activities such as walking and tea picking—among middle-aged and elderly participants.

Methods

Experimental location

The Chashoushan Forest Health Care Base, situated in Zunyi City in northeastern Guizhou Province, China, was selected as the experimental site for this study (Fig. 1). The site lies at an altitude of 1,300 m, covers an area of 5,800 acres, and is characterized by an average annual temperature of 15.2 °C, summer temperatures not exceeding 24 °C, an average annual humidity of 79%, a forest coverage rate of 86%, consistently excellent air quality (100%), and a NAI concentration exceeding 5,000 ions/cm3. To ensure scientific rigor and comparability, an urban area in Fenggang County—located within 5° of latitude and longitude at a similar altitude—was selected as the control environment.

Fig. 1
figure 1

Itinerary of the subjects for each day during the experiment.

Note: The regular work in the itinerary is mental work within the test site.

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Participants

Between April and June 2024, 53 middle-aged and elderly electrical automation practitioners residing long-term in urban environments were recruited through a hybrid “online and on-site” method. After strict screening by a team of professional physicians based on predefined inclusion and exclusion criteria, 34 participants aged 30–62 years were ultimately enrolled. The experimental group (EG) comprised 18 participants with a mean age of 48.11 ± 7.53 years, while the control group (CG) included 16 participants with a mean age of 48.94 ± 8.84 years(Table 1). From June 25 to June 30, 2024, a five-day, four-night intervention was conducted. The EG engaged in tea forest-based activities such as walking and understory picking, while the CG performed walking or routine activities in the urban environment of the same region. Inclusion criteria were as follows: (1) absence of psychiatric disorders and capacity for independent living; (2) Sub-health Measurement Scale Version 1.0 (SHMS V1.0) score ≥ 40; (3) age between 40 and 60 years; and (4) no prior participation in forest recreation or similar experiences within the past six months. Exclusion criteria included the presence of severe cardiac, hepatic, splenic, pulmonary, or renal diseases; immune or infectious diseases; substance dependence (including alcohol, cocaine, or other drugs); and pregnancy.

The recruitment process adhered to the ethical principles of the 1964 Declaration of Helsinki and its subsequent amendments or equivalent ethical standards. The study protocol received approval from the Ethics Committee of Guizhou Medical University. Detailed information about the study was provided to all participants, and written informed consent was obtained prior to their inclusion.

Study design and procedures

Throughout the experimental period, weather conditions in both environments—tea forest and urban—were consistently clear to overcast, with no significant differences in altitude or atmospheric pressure between the two sites. Daily wellness interventions were conducted in accordance with the pre-established health activity schedule (Fig. 1). On June 24, 2024, all participants convened at the designated assembly point. To minimize external influences on emotional states, participants were instructed to refrain from engaging in stimulating behaviors, such as alcohol consumption, for the duration of the study. Participants in EG were accommodated in a hotel located within 500 m of the forest health base and engaged in health activities within the tea forest environment for a minimum of three hours daily. Participants in CG resided in an urban hotel and performed comparable activities in the city environment during the same rest periods. To ensure consistency and scientific validity, dietary intake and macronutrient ratios were standardized across groups, with meal plans designed by certified clinical dietitians. Physical activity levels were regulated through daily step counts (8,000–9,000 steps), tracked via the WeChat pedometer, to control for exercise-induced variability in outcomes.

Experimental indicators

Environmental characteristic parameters

Environmental parameters—including noise levels, temperature, relative humidity, wind speed, and NAI concentration—were monitored using a multifunctional sound level meter, a portable handheld weather station, and a negative ion detector. Measurements were taken every two hours between 9:00 and 17:00 daily in both environments (Table 2). Human thermal comfort was assessed using the Human Comfort Index (HCI) as proposed by Lu Dinghuang et al.43, with the calculation formula detailed below:

Table 1 Subject demographic characteristics.
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Table 2 Summary of instruments and equipment.
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$$\:\text{H}\text{C}\text{I}=0.6\times\:\left|\text{T}-24\right|+0.07\times\:\left|\text{H}-70\right|+0.5\times\:\left|\text{V}-2\right|$$

where T represents the air temperature in ℃, H represents the relative humidity in %, and V represents the wind speed in m/s.

Volatile organic Compounds(VOCs)

On a sunny, windless day, air samples and fresh plant material were collected from both the tea forest and urban environments under matched conditions, including similar vegetation age, growth environment, and plant physiological status, with no signs of disease. Samples were obtained at 9:00, 11:00, 13:00, 15:00, and 17:00 using a vacuum gas sampler to assess VOCs. Fresh leaves and twigs were placed in sampling bags and preserved in dry ice containers or iceboxes to ensure sample integrity.

Physiological measures

Blood pressure, peripheral oxygen saturation, pulse rate measurements

On the first and final days of the intervention, after a minimum of five minutes of seated rest, participants underwent physiological assessments including SBP, DBP, peripheral oxygen saturation (SpO2), and pulse rate (PR). These parameters were measured three times on the left arm using a multiparameter physiological monitor, and average values were recorded.

Lymphocyte subpopulation measurements

Venous blood samples (2 mL) were collected at 8:00 AM on both the first and final days of the study. Fasting blood was drawn from the antecubital vein using sterile blood collection systems by two trained healthcare professionals. Samples were maintained at 4 °C in refrigerated conditions or a water bath before being transported to the Guizhou Jinyu Medical Testing Center for analysis. Flow cytometry was employed to quantify suppressor T cells (CD8+), helper T cells (CD4+), NK cells, total lymphocytes (CD56+), and the CD3 + CD4+/CD3 + CD8 + T cell ratio.

All equipment that came into direct contact with participants was thoroughly disinfected before and after each use. Strict hand hygiene protocols were observed by researchers, including the use of disinfectant solutions prior to and following each participant interaction.

Psychological measures

Mood state

The Profile of Mood States (POMS), as revised by Zhu Beili44, was employed to assess participants’ emotional states before and after the wellness intervention. The scale comprises seven subscales: tension–anxiety (T-A), anger–hostility (A-H), depression (D), vigor (V), confusion (C), fatigue (F), and self-esteem. The Total Mood Disturbance (TMD) score is derived by summing the scores of the five negative emotion subscales (T-A, A-H, D, C, F), subtracting the scores of the two positive emotion subscales (V and self-esteem), and adding a constant of 100 for normalization. Higher TMD scores reflect more severe emotional disturbance45. In the current study, the POMS demonstrated high internal consistency, with a Cronbach’s alpha of 0.94 and a McDonald’s omega of 0.76.

Sleep quality

Sleep quality was assessed using the revised Pittsburgh Sleep Quality Index (PSQI), adapted by Liu Xianchen et al.46. The instrument evaluates seven components: subjective sleep quality, sleep latency, sleep duration, habitual sleep efficiency, sleep disturbances, use of sleep medication, and daytime dysfunction. A total score exceeding 7 indicates poor sleep quality47, with lower scores corresponding to better sleep outcomes. The PSQI demonstrated strong reliability in this study, with a Cronbach’s alpha of 0.85 and a McDonald’s omega of 0.73.

Statistical analysis

All physiological and psychological data were compiled and subjected to statistical analysis. A normality test was conducted to assess the distribution characteristics of the sample data. Depending on the results of this test, within-group comparisons before and after the intervention were analyzed using either paired-sample t-tests or Wilcoxon signed-rank tests. Between-group differences post-intervention were assessed using independent-sample t-tests or Mann–Whitney U tests. Statistical significance was determined at the threshold of p < 0.05.

Results

Monitoring of environmental parameters

During the recuperation period, the average daily concentration of NAIs in the tea forest environment consistently exceeded 1,000 ions/cm3, with the lowest recorded value being 1,671.80 ± 248.73 ions/cm3. Peak NAI concentrations occurred between 11:00 a.m. and 3:00 p.m. In contrast, the city environment exhibited significantly lower NAI levels, with a maximum concentration of 942.40 ± 24.00 ions/cm3. Air pollutant levels in the tea forest were markedly lower, and the air quality was consistently rated as “excellent.” According to the HCI derived from Eq. 1, participants experienced greater thermal comfort in the tea forest environment (HCI = 3.36) compared to the city environment (HCI = 3.69). Additionally, the average ambient noise level in the tea forest remained below 50 dB, whereas the city environment recorded higher noise levels ranging from 60 to 80 dB, compromising environmental tranquility. Collectively, the superior NAI concentration, enhanced comfort, lower noise levels, and better air quality in the tea forest environment provide favorable conditions for recreational health activities (Fig. 2).

Fig. 2
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Changes in daytime Negative air ion concentration, Human comfort indext, Noise level, and air pollutant concentration at different locations.

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Volatile organic compounds (VOCs)

During Analysis of fresh leaf and branch samples identified 104 VOCs species in the tea forest environment. Among these, esters were the most prevalent (27 species, 57.07%), followed by alcohols (21 species, 21.96%), aromatic hydrocarbons (7 species, 7.33%), terpenes (18 species, 4.66%), aldehydes (7 species, 3.16%), alkanes (10 species, 0.69%), and ketones (5 species, 0.34%). In the city environment, 98 species were detected, with esters accounting for 26 species (38.40%), alcohols 21 species (33.77%), aromatic hydrocarbons 1 species (1.58%), terpenes 16 species (4.43%), aldehydes 13 species (3.92%), alkanes 9 species (1.06%), and ketones 6 species (1.16%).

VOCs analysis of air samples further revealed 87 species in the tea forest environment, with peak concentrations observed between 12:00 and 14:00. These included 7 esters, 1 alcohol, 6 aromatic hydrocarbons, 10 terpenes, 4 aldehydes, 2 ketones, and 36 alkanes. In contrast, 143 VOC species were detected in the city environment, comprising 31 esters, 20 alcohols, 8 aromatic hydrocarbons, 20 terpenes, 15 aldehydes, 6 ketones, and 43 alkanes (Fig. 3).

Fig. 3
figure 3figure 3

Changes in VOCs at different locations.

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Effects of tea forest recreation on human physiological indicators

Effect of tea forest recreation on blood pressure, peripheral oxygen saturation and pulse rate

No significant differences were observed in baseline physiological indicators between EG and CG prior to the intervention. Following the recuperation period, the CG showed modest improvements: SBP decreased from 125.83 ± 11.46 mmHg to 124.61 ± 12.01 mmHg, and PR declined from 85.50 ± 9.17 beats/min to 84.17 ± 8.83 beats/min (P < 0.05). Changes in DBP and SpO2 were not statistically significant. In the EG, significant reductions were observed in SBP (from 123.05 ± 8.84 to 118.50 ± 7.25 mmHg), DBP (from 101.90 ± 8.72 to 98.95 ± 8.86 mmHg), and PR (from 87.90 ± 9.31 to 81.25 ± 8.94 beats/min) (P < 0.05). No significant change was noted in SpO2. Compared to the CG, no statistically significant post-intervention differences were observed between groups in SBP, DBP, or PR. However, a decrease in SpO2 was noted in the EG (from 96.15 ± 1.87% to 94.89 ± 1.23%). These findings suggest that Cha-lin recuperation effectively reduces blood pressure and heart rate, thereby enhancing cardiovascular resilience and supporting respiratory-circulatory function (Fig. 4).

Fig. 4
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Blood pressure, peripheral oxygen saturation, pulse rate before and after analysis results.

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Impact of tea forest recreation on human immune functions

Immunological indicators did not differ significantly between groups prior to intervention. Post-recuperation, the CG exhibited a significant increase in CD8 + T cells (from 478.69 ± 206.30 to 493.88 ± 206.54 cells/µL), while other immune indices remained unchanged. In contrast, the EG showed multiple significant improvements: CD4 + T cells increased from 634.06 ± 228.21 to 758.94 ± 272.06 cells/µL, NK cells from 362.17 ± 151.74 to 461.00 ± 211.57 cells/µL, and CD56 + cells from 1862.00 ± 556.45 to 1987.50 ± 592.48 cells/µL. Additionally, the CD3 + CD4+/CD3 + CD8 + T cell ratio increased from 1.30 ± 0.67 to 2.16 ± 1.51, while CD8 + T cells decreased from 569.67 ± 252.72 to 441.61 ± 206.03 cells/µL. These changes indicate a strengthened immune response and reduced immune dysfunction following forest-based intervention, highlighting the positive immunomodulatory effects of tea forest recreation (Fig. 5).

Fig. 5
figure 5

CD4, CD8, CD3 + CD4 + T cells/CD3 + CD8 + T cells, NK cells, CD56 before and after analysis results.

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Impact of tea forest recreation on the mental health of the population

Tea forest recreation helps to regulate the state of Mind

Baseline mood state scores showed no significant differences between groups. Post-intervention, the CG exhibited no significant improvements in mood parameters, with the exception of slight reductions in A-H, F, and C. In contrast, the EG demonstrated substantial improvements: T-A decreased from 3.32 ± 1.34 to 2.14 ± 1.11, F from 3.14 ± 1.27 to 1.86 ± 1.56, and D from 1.79 ± 1.50 to 0.93 ± 0.66, while V increased significantly from 5.00 ± 2.43 to 11.68 ± 4.03. The TMD score declined from 105.14 ± 4.65 to 91.75 ± 5.04. Compared to the CG, the EG exhibited significantly reduced negative emotions, enhanced positive affect, and marked overall improvements in psychological well-being, confirming the beneficial effects of tea forest recuperation on mental health (Fig. 6).

Fig. 6
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The mood state changes before and after analysis results.

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Tea forest recreation is favorable to the improvement of sleep quality

No significant difference in baseline sleep quality scores was observed between the two groups. Following the recuperation period, CG showed moderate improvements in sleep onset and sleep duration, likely attributable to reduced occupational demands, increased social interaction, and a more relaxed living environment. In EG, post-intervention scores for sleep onset (from 1.90 ± 0.70 to 0.26 ± 0.51), sleep duration (from 1.68 ± 0.91 to 0.68 ± 0.54), and sleep disturbances (from 2.29 ± 0.46 to 1.10 ± 0.75) were significantly reduced. The total PSQI score decreased markedly from 10.13 ± 1.50 to 6.90 ± 1.33 (p < 0.05). Compared to CG’s post-rehabilitation score (9.30 ± 1.39), EG exhibited a significantly lower total PSQI score, along with substantial reductions across all subscales of the PSQI. These results suggest that recuperation in the tea forest environment effectively alleviates sleep disturbances, enhances sleep quality, and subsequently contributes to improved quality of life and work performance (Fig. 7).

Fig. 7
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The sleep quality improvement before and after analysis results.

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Discussions

The adverse effects of environmental pollution on human health have garnered increasing global concern. According to the 2021 Global Burden of Disease Report48, air pollution and abnormal temperature patterns have emerged as leading contributors to the global disease burden. Air pollution alone accounted for approximately 8.1 million deaths worldwide, ranking as the second leading risk factor for mortality globally. The concentration of NAIs is recognized as a critical indicator of air quality. In urban settings and enclosed indoor environments, NAI concentrations often fall below 500 ions/cm3, a level associated with detrimental effects on the respiratory, circulatory, immune, and nervous systems. In contrast, natural environments typically exhibit NAI concentrations exceeding 1,000 ions/cm3, a threshold indicative of favorable environmental conditions that promote health. During the present study, the tea forest environment consistently maintained NAI concentrations above 1,000 ions/cm3, while the urban environment registered significantly lower levels. From a medical standpoint, prolonged exposure to environments with NAI concentrations ranging between 1,000 and 5,000 ions/cm3 exerts beneficial regulatory effects on the immune system, enhancing immune function and increasing resistance to disease. When NAI levels reach 5,000–10,000 ions/cm3, their potent oxidative capacity enables the disruption of bacterial cell structures, resulting in effective airborne disinfection and a substantially reduced risk of infectious disease transmission49,50,51. Individuals with chronic conditions such as bronchitis, emphysema, coronary artery disease, and hypertension frequently report marked symptom relief following even short-term exposure to natural settings such as coastal areas or forested landscapes characterized by lush vegetation and clean air52.

Particulate matter (PM), particularly PM2.5, was identified in 2021 as the leading risk factor contributing to disability-adjusted life years (DALYs), accounting for 8.0% of the global total. Both epidemiological and toxicological evidence have linked PM2.5 exposure to a broad spectrum of health conditions, including asthma, impaired pulmonary function, structural lung changes, respiratory inflammation, immunosuppression, cardiovascular events, and malignancies53,54,55,56,57,58,59,60,61. In addition to PM2.5, air pollutants such as ozone (O3), nitrogen dioxide (NO2), sulfur dioxide (SO2), carbon monoxide (CO), and carbon dioxide (CO2) have been associated with adverse effects on the respiratory, cardiovascular, nervous, and musculoskeletal systems, as well as with negative impacts on mental health and behavior62,63,64,65,66. The results of this study confirm that the tea forest environment exhibits superior air quality, reduced noise levels, elevated NAI concentrations, favorable HCI scores, and an abundance of health-promoting VOCs—collectively indicating its suitability for human habitation and its potential for supporting physical and psychological well-being.

According to a report by China Meteorological News, human comfort is strongly influenced by environmental temperature and humidity. Optimal comfort is experienced when ambient temperatures range from 18℃ to 25 ℃and relative humidity falls between 40% and 70%. When temperatures rise to 26 ℃–30 ℃ and relative humidity remains below 60%, individuals may feel warm but not uncomfortably so. However, temperatures exceeding 30℃ combined with relative humidity above 70% typically result in pronounced discomfort due to oppressive heat. The China Meteorological Administration’s 2023 Blue Book on Climate Change in China reported that the nation’s climate continues to warm, with the average surface temperature in 2022 being 0.92 ℃ higher than the historical mean67. Climate change intensifies the urban heat island effect, which has a direct and measurable impact on public health in urban areas68,69. Ambient noise levels also play a critical role in human comfort. A sound environment ranging from 30 to 40 dB is generally perceived as quiet and conducive to relaxation. Once noise levels exceed 50 dB, sleep and rest may be disrupted, leading to persistent physical and mental fatigue and impairing normal physiological functions. At levels above 70 dB, conversational clarity diminishes, concentration becomes difficult, and declines in work efficiency and overall quality of life are observed. Prolonged exposure to noise levels exceeding 90 dB poses significant risks of hearing impairment and other health disorders70.

VOCs, also known as phytoncides or plant essences, are gaseous substances emitted from forest plants under natural conditions. These bioactive compounds can be absorbed through respiration and skin, producing therapeutic effects on human health71,72. The VOC profile of the tea forest environment includes ketones (e.g., cis-jasmonone, β-ionone), alcohols (e.g., linalool, geraniol), aldehydes (e.g., nerolidehyde, citral, geranium aldehyde), terpenes (e.g., β-myrcene, D-limonene, caryophyllene, α-farnesene, alpha-cuparene), and esters (e.g., cis-3-hexenyl cis-3-hexenoate), aligning with findings by He et al.73. Compounds such as β-ionone, D-limonene, β-myrcene, linalool, caryophyllene, and citral exhibit antioxidant, anti-inflammatory, immunomodulatory, and analgesic properties. These VOCs have demonstrated efficacy in alleviating anxiety and depression symptoms and show promise in research related to cancer, inflammation, and infectious diseases74,75,76,77,78,79,80. In contrast, harmful VOCs—including styrene, toluene, ethylbenzene, and para-/ortho-xylene—isomers—were detected at low concentrations in urban environments, primarily due to industrial emissions, vehicle exhaust, solvent use, and fuel evaporation. Benzene, toluene, and ethylbenzene are listed on China’s Environmental Priority Pollutant Blacklist81 and are also classified as priority pollutants by the United States Environmental Protection Agency. Benzene exposure via inhalation, ingestion, or dermal absorption is closely associated with increased leukemia risk. Toluene exerts neurotoxic and hematotoxic effects, while other aromatic hydrocarbons such as ethylbenzene and styrene pose additional health hazards82,83,84.

Research by Song, Lee, and colleagues demonstrated that short-term forest walks significantly reduced heart rate in both young men and women84,85,86. A field study conducted across 24 certified forest therapy bases in Japan similarly reported that forest environments led to reductions in PR and blood pressure, enhanced parasympathetic nervous system activity, and decreased sympathetic activation when compared to urban settings27. Although inter-individual variability may obscure statistical significance in some physiological indicators, tea forest recuperation, when compared to urban exposure, exerted a measurable positive impact on physiological health. In the present study, participants exposed to the tea forest environment exhibited reductions in blood pressure and PR, along with increased SpO2. Environmental influences have been shown to exert a stronger effect on immune function than genetic factors87,88. Chronic stress is known to suppress immune responses and promote dysregulated or pathological immunity89,90. The immune system depends on maintaining stable proportions and interactions among lymphocyte subtypes to preserve homeostasis and immune competence. One critical marker of immune regulation, the CD3 + CD4+/CD3 + CD8 + T cell ratio, typically ranges from 0.71 to 2.78 in healthy adults. Stress has been found to disrupt this ratio and impair immune responses, as reported by Steptoe and Segerstrom91,92. In the current study, participants in EG experienced significant increases in helper T lymphocytes, NK cells, and total lymphocyte counts following tea forest recuperation. In contrast, immune cell levels in CG exhibited only marginal and statistically non-significant changes, suggesting that the tea forest intervention contributed meaningfully to improved immune function. Previous studies further support these findings: after “3 days and 2 nights” of forest therapy, significant increases were observed in peripheral CD3 + lymphocytes and CD56 + NK cells, along with elevated levels of cytotoxic proteins including perforin, granzyme, and granulysin93. A five-day/four-night forest immersion similarly resulted in a marked increase in activated NK cells, with post-intervention levels significantly higher in forest-exposed individuals than in those in urban environments94. Additionally, 12 weeks of forest walking in VOC-rich environments led to increased NK cell counts and elevated blood melatonin levels among middle-aged women95. The beneficial effects on NK cell quantity and activity have been shown to persist for at least seven days following forest exposure24,96.

Grilli et al. reported a positive correlation between forest exposure and psychological well-being26. In this experiment, participants demonstrated reduced negative emotional states, enhanced positive emotions, improved mood stability, and significantly better sleep quality following tea forest rehabilitation. These findings are consistent with existing literature, which indicates that forest bathing alleviates negative affective symptoms while enhancing positive mood, contributing to improved mental health97. Populations including young women, military personnel, and individuals with chronic illness have reported notable improvements in sleep quality, work performance, and overall quality of life following participation in forest-based health interventions98,99.

Conclusions

In summary, compared to urban environments, the tea forest environment is characterized by a significantly higher concentration of NAIs, a “very comfortable” HCI, elevated environmental tranquility, and an “excellent” air quality rating. It also exhibits greater diversity and concentration of VOCs, particularly beneficial phytoncides such as β-ionone, D-limonene, β-myrcene, linalool, and caryophyllene. These features collectively contribute to a high-quality ecological setting favorable for health-promoting interventions.

Following exposure to the tea forest environment, middle-aged and elderly participants experienced reductions in blood pressure and PR, along with increased SpO2. Immunological improvements were also observed, including significant increases in lymphocyte subsets, an elevated CD3 + CD4+/CD3 + CD8 + T cell ratio, and reductions in suppressor T cells. Psychological benefits included enhanced mood states and improved sleep quality, further underscoring the therapeutic value of the tea forest environment.

This study aimed to evaluate the influence of tea forest environments on the physical and mental health of middle-aged and elderly individuals, offering meaningful reference value for forest-based healthcare practices. Nonetheless, the limited sample size and inter-individual variability may constrain the generalizability and statistical power of the findings. Future research should prioritize expanding the sample size, minimizing individual differences, and broadening the participant population to include individuals with psychological disorders, cardiovascular disease, chronic obstructive pulmonary disease, and cancer, thereby comprehensively assessing the health benefits of tea forest rehabilitation.