A Meta-Analysis of the Intervention Effects of Horticultural Therapy on Elderly Patients with Dementia

Objective Horticultural therapy is an important non-pharmacological intervention for dementia, but its impact on different evaluation dimensions remains to be clarified. This paper systematically summarizes the dimensions of the impact of horticultural therapy on patients with dementia, analyzes the heterogeneity of the intervention effects of patients’ basic characteristics and intervention program features, identifies the key modulating factors for optimizing intervention effects, and provides evidence-based support for the formulation of precise intervention programs.

Methods This paper adopts a systematic literature review method, referring to the “Preferred Reporting Items for Systematic Reviews and Meta-Analyses” (PRISMA) framework, and collects and analyzes literature from multiple disciplines such as medicine, environmental science, and landscape architecture. Seven databases, including CNKI, Wanfang Database, SinoMed, Web of Science, PubMed, Embase, and Cochrane Library, were searched from the establishment of the databases until December 31, 2025. Data analysis was conducted using the Meta package in R 4.5.2 software, and subgroup analysis was performed based on pre-specified factors such as patients’ basic conditions and intervention program features. The stability of this study was evaluated through sensitivity analysis, and publication bias was tested using Egger’s test and funnel plots.

Results After strict screening according to the pre-specified inclusion and exclusion criteria, 16 articles that met the requirements of this study were selected for meta-analysis, involving a total of 1,278 research subjects. The included literature covered more than 40 measurement scales and assessment indicators in areas such as physical function, biomarkers, neuropsychology, mental behavior, and quality of life. By summarizing indicators that reflect the same or highly related aspects, they can be systematically integrated into three dimensions: cognitive function, mental health, and physical health. Cognitive assessment covers screening, domain-specific, and quality of life impact; physical health evaluation integrates physical function, physiological systems, and daily activity ability; mental health assessment includes emotional disorders, mental behavior symptoms, and social psychological functionings. Subgroup analysis was conducted based on the sources of heterogeneity between studies, comprehensively considering patients’ basic conditions and intervention program features. Among them, patients’ basic conditions include three-dimensional factors such as disease stage, education level, and intervention site. The effects of horticultural therapy vary in different disease stages, patients’ education levels, and intervention sites. The effect is most significant and the evidence is robust in the moderate disease stage (d_sm=0.68), similar but with heterogeneity in the mild stage, and weaker in the delirium stage; patients with the lowest education level (<7 years) benefit the most (d_sm=0.82), while a “plateau effect” occurs in higher education levels; the effect is optimal and stable in long-term care institutions (d_sm=0.80), moderate to high in the community, and similar but with higher heterogeneity in hospitals, and the conclusions need further verification; intervention program features include four-dimensional factors such as intervention period, intervention frequency, intervention duration, and intervention method. The effect is the greatest in long-term intervention periods (≥32 weeks) but the evidence is inconsistent (d_sm=0.83); intervention frequency is significantly positively correlated with efficacy, with 4 to 5 times per week being the best (d_sm=0.99); intervention duration shows a negative correlation trend with effect, with ≤30 minutes being the most significant (d_sm=0.97), but the sample size is limited; among intervention methods, VR horticultural therapy has the highest effect size (d_sm=0.72), but there are few studies; outdoor horticultural therapy has the most stable effect (d_sm=0.62), and indoor horticultural therapy has higher heterogeneity.

Conclusion Systematic reviews reveal that horticultural therapy demonstrates positive effects across three dimensions: cognitive function, mental health, and physical health. Cognitively, multisensory stimulation activates the brainstem reticular formation, enhancing attention, memory, and executive function. Psychologically, it effectively alleviates depression and anxiety, and reduces stress levels. Physiologically, it improves hand-eye coordination, muscle strength, sleep quality, and immune function. Although the overall effect is relatively small, it is statistically significant. In terms of application characteristics, patients in the moderate stage benefit the most, those with low educational levels have the greatest marginal benefit, and long-term care institutions and community settings are more effective than hospitals. Regarding intervention programs, long-term and high-frequency interventions are more effective; outdoor real environments are superior to virtual or indoor environments; and mid-term interventions strike a balance between novelty and adaptability. This study provides empirical support for non-pharmacological interventions. Horticultural therapy, with its low risk, high acceptability, and multiple benefits, is of great significance in the context of an aging population. Future research should conduct more rigorous large-sample, long-term studies to deeply analyze the effects of patient characteristics and intervention elements on therapeutic effects, providing a more solid evidence base for optimizing clinical applications.