Effect of Horticultural Therapy on Frontal Lobe Cognitive Function in Older Adults with Dementia
Article information
Abstract
Background and objective
This study was conducted to determine the effect of a horticultural therapy program on frontal lobe function, which is a component of cognitive function, in the elderly users of an adult day-care center.
Methods
Horticultural therapy programs were carried out once a week for a total of 8 sessions from March 8 to April 26, 2023. A total of 27 older adults with dementia were targeted, with 10 in the control and 17 subjects in the experimental group.
Results
When homogeneity was tested between the control and experimental groups before the horticultural therapy program, there were no statistically significant differences in all items, including Go/No-Go (p = .393), Digit Span (p = .690), Word Fluency (p = .157) and Concentration/Distractibility (p = .169), indicating that the groups were homogeneous. The control group showed no significant differences in Go/No-Go (p = .132), Digit Span (p = .257), Word Fluency (p = .062) and Concentration/Distractibility (p = .180). However, the experimental group showed statistically significant differences in Go/No-Go (p = .001), Digit Span (p = .001), Word Fluency (p = .038) and Concentration/Distractibility (p = .007).
Conclusion
Therefore, the experimental group had lower evaluation scores than the control, indicating that the horticultural therapy program had an effect on cognitive function in the frontal lobe. The process of analyzing cognitive function of dementia patients can be said to be an important process to predict potential intervention techniques. It is hoped that horticultural therapy for the older adults with dementia will be effective in improving cognitive function and that these programs will be actively used to recognize the older adults with dementia.
Introduction
Dementia is an acquired disease that occurs when brain function is damaged, resulting in a progressive decline in one or more of the cognitive domains, including concentration, memory, language, perception, and executive functions, making it difficult for someone to manage their daily tasks (Lee et al., 2021; Sachdev et al., 2014). Alzheimer’s disease, which accounts for approximately 70% of all dementia cases, causes dementia symptoms due to degeneration of the brain cells, while vascular dementia, which accounts for the remaining 20–30%, occurs when brain tissue is damaged by cerebrovascular disease, causing a decline in brain function (Jung et al., 2022). Cognitive impairment is common in dementia and in stroke patients, and is known to be closely related to the state of the brain (Kim and Im, 2015). Early detection of dementia allows for improvement in symptoms, maintenance of some level of daily life functioning, and prevention of worsening symptoms with appropriate treatment. Therefore, interventions that can improve cognitive function and delay the progression of symptoms in older adults with dementia (OAD) are urgently needed (Ji et al., 2004).
Horticultural therapy with plants is an intervention technique that allows for mental and physical healing by stimulating the human sensory organs and allowing people to connect with the natural world (Son et al., 1997). As horticultural therapy has been reported to be effective in increasing mental stability and achieving physical improvements in various subjects (Ulrich, 1990), much research has been conducted on OAD. As a result, horticultural therapy has been shown to improve cognitive, emotional, psychosocial, and physical functioning in OAD (Kang and Kang, 2021). Horticultural therapy has been recognized as a new medical technology for cognitive intervention treatment (Ministry of Health and Welfare Notification No. 2017-125), and medical institutions can now prescribe the therapy as one of the items not covered by the National Health Insurance (NHI) for patients with mild cognitive impairment or dementia (Korean Horticultural Therapy Welfare Association, 2019).
The frontal lobe, located in the front part of the cerebral hemisphere, is responsible for important cognitive functions such as thinking, planning, reasoning, problem solving, judgment, emotions, and behavioral control. When the frontal lobe is damaged, various symptoms may result, including executive function disorder, speech problems, difficulty concentrating, memory problems, poor judgment, difficulty controlling emotions, and executive dysfunction (Oh, 2010). In horticultural therapy, simply looking at plants helps activate brain functions such as the frontal and temporal regions, and increases activity in areas responsible for memory and thinking (Son, 1999). The cognitive functions of the frontal lobe are known to decline more rapidly with age than those of other regions; abilities such as concentration and word fluency have been found to decline with age (Park, 2004). The decline in cognitive functions of the frontal lobe has been found to be particularly pronounced in the oldest-old (Lee, 2021). The executive function deficits that appear in the early stages of dementia are associated with the degeneration of the prefrontal cortex (PFC) of the cerebrum (Nathan et al., 2001). In cases of dementia or lesions in the cerebral cortex, scores on neuropsychological tests that require executive function, such as word fluency, are low, and ineffective neural activity in the frontal cortex (FC) is observed (Lee and Kim, 2019). Executive function deficits can be accompanied by declines in other cognitive functions, which can lead to impairments in activities of daily living in older adults (Jung et al., 2022). As the degeneration of the PFC of the cerebrum progresses, neurocognitive problems occur due to changes in cognitive function, and most age-related neurocognitive disorders are dementia (Park, 2019). To date, there has been no research on the effects of horticultural therapy on frontal lobe cognitive function in OAD.
Dementia is a progressive disease, and many tools have been introduced to help screen and clinically evaluate patients with dementia (Shin, 2010). The Alzheimer’s Disease Assessment Scale (ADAS) was developed as a diagnostic tool to assess the level of cognitive and non-cognitive symptoms in patients with Alzheimer’s disease (Rosen et al., 1984). Through several previous studies, the Korean version of the Alzheimer’s Disease Assessment Scale-Cognitive Subscale (ADAS-Cog-K) has been shown to be a cognitive assessment tool with high reliability and validity (Suh and Mohs, 2003). It is known to be useful for screening dementia patients or determining the type of dementia, as it includes various cognitive domains, including concentration, memory, language ability, visuospatial ability, executive function, and frontal lobe function (Kim and Im, 2015; Kim et al., 2007).
The purpose of this study was to develop a horticultural therapy program using items that can assess frontal lobe function in the ADAS-K-Cog, and to examine its effects on cognitive function. It also aimed to provide baseline data that can be actively used in future interventions for OAD who are admitted to nursing homes.
Research Methods
Subjects
The subjects were 27 older adults with mild dementia who used K Daycare Center in City G, excluding those with severe dementia who were unable to communicate. More than 90% of the subjects who participated in this experiment had Alzheimer’s disease, not vascular dementia. They were diagnosed with dementia based on the medical opinions of neurosurgeons capable of diagnosing dementia, and on brain tests (MRI, PET-CT, etc.) and neuropsychological tests.
The control group consisted of 10 subjects (1 male, 9 females) with a mean age of 82.3 ± 4.9 years and a cognitive function (MMSE) score of 19.4 ± 3.0 points, while the experimental group consisted of 17 subjects (4 males, 13 females) with a mean age of 80.7 ± 5.1 years and a cognitive function (MMSE) score of 18.9 ± 2.3 points (Table 1). In addition to dementia, most subjects had at least one chronic disease, including cerebral infarction, diabetes, hypertension, degenerative arthritis, heart disease, Parkinson’s disease, and panic disorder. All subject selected could hear, see, move, communicate, and follow basic instructions to receive horticultural therapy. Informed consent was obtained both from family caregivers and from the subjects, and approval was obtained from the Institutional Bioethics Committee (CUIRB-2022-0073).
Research tools
Horticultural therapy program
The composition of horticultural therapy programs was decided after prior consultation with the staff of the K Daycare Center, and materials were selected that were relatively easy to handle and safe within the scope of the subjects’ physical activity abilities. The steps were simplified to consist of activities within a feasible range for them.
From March 8 to April 26, 2023, horticultural therapy programs were delivered to the experimental group on Wednesday afternoons, once a week for 1 hour per session, for a total of 8 sessions. The programs were conducted by the researcher (a Ph.D. student in horticultural therapy) and five horticultural therapists (Korea Horticultural Therapy and Welfare Association (KHTA)). Subjects were instructed in horticultural activities that they could actually perform, including arranging flowers, cutting, knotting, folding paper boxes, taping, writing, applying glue, packaging, planting, and putting in soil. They also performed activities such as answering questions about the types of flowers that bloom in spring, arranging flowers according to numbers, and making paper boxes using tools (Table 2).
Assessment tools and cognitive intervention
The Alzheimer’s Disease Assessment Scale-Cognitive Subscale-preliminary Korean version (ADAS-Cog-K) was used in this study (Korean Association for Geriatric Psychiatry, 2021). The translated version, ADAS-Cog-K, comprehensively covers several cognitive domains, including concentration, memory, language ability, visuospatial ability, executive function, and frontal lobe (FL) function. Among these, FL function consists of items such as Go/No-Go, Digit Span, Word Fluency, and Concentration/Distractibility. Therapeutic interventions in the horticultural therapy programs were attempted for each item based on the items of the ADAS-Cog-K, and assessments were made both before and after the programs to examine changes in FL cognitive function. Lower scores indicate better cognitive functioning.
Go/No-Go evaluates subjects’ responses by asking them to respond to only one of two signals presented by an evaluator and not the other, and the number of incorrect responses from a total of 40 items is scored from 0 to 5 points. As a cognitive intervention for the Go/No-Go tasks, subjects were instructed to perform hand movements such as putting in two spoonfuls of stones and taking out one spoonful with a spoon in hydroponics, and all tasks were divided into steps so that they could follow along by responding to the given signals.
Digit Span tasks are administered in both forward and backward order, with subjects repeating the numbers in the order presented by an evaluator or repeating them in reverse order. The tasks are scored by awarding subjects one point for each sequence of numbers correctly recalled, per trial and direction, ranging from 0 to 5 points. As a cognitive intervention for the tasks, the making of carrier boxes was implemented, and subjects were asked not only to count the materials, but also to memorize the numbers. They were also asked to recall the numbers and work steps every 10 minutes.
Word Fluency is a test that assesses subjects’ ability to produce words within a time limit, and can detect and differentiate the decline of frontal lobe function by assessing the productivity of thinking. As a cognitive intervention, subjects were given one minute each to name the materials and list the items that can be purchased in flower shops; they were asked to produce as many words as possible in the given time.
Concentration/Distractibility is a test that examines subjects undergoing horticultural therapy programs by closely observing them, considering the conversation that was held at the beginning of the test and all the processes during the test, to determine if they have difficulty concentrating or are distractible. It is designed to help increase subjects’ concentration by providing activities that can be easily performed through cognitive intervention.
Data analysis
SPSS Statistics software (version 19.0, IBM, USA, 2012) was used to analyze the results. The Mann-Whitney U test was used to compare the pre- and post-test means between the control and experimental groups in the assessment of frontal lobe function, and the Wilcoxon signed-rank test was used to compare the pre- and post-test means within each group.
Results and Discussion
This study was conducted to examine the effects of horticultural therapy programs on frontal lobe function related to the cognitive domain of older adults with dementia in daycare centers. When homogeneity was tested between the control and experimental groups before the horticultural therapy programs, there was no statistically significant difference for any of the items: Go/No-Go (p = .393), Digit Span (p = . 690), Word Fluency (p = .157), and Concentration/Distractibility (p = .169), indicating that the groups were homogeneous (Table 3).
Comparing the means between the control and experimental groups after horticultural therapy programs, there was a significant difference in Go/No-Go, with the control group scoring 2.90 points and the experimental group scoring 1.00 points (p = . 001). However, there was no significant difference between the groups in Digit Span (p = .063), Word Fluency (p = .505), and Concentration/Distractibility (p = .053). In the Go/No-Go task, subjects were asked to respond by performing a finger movement (Go) or inhibiting it (No-Go). It appears that not only was the horticultural therapy program, which involved a lot of finger movement, effective, but also that subjects may have responded more easily to the task using their bodies compared to other items assessed while speaking.
When Go/No-Go, Digit Span, Word Fluency, and Concentration/Distractibility of the subjects were evaluated both before and after the programs, the comparison of means within the control group showed that there was no significant difference for any of the items. However, within the experimental group, there was a significant difference in all four items: from 2.88 to 1.00 points (p = . 001) for Go/No-Go, from 3.58 to 2.52 (p = .001) for Digit Span, from 2.41 to 1.88 (p = .038) for Word Fluency, and from 3.52 to 3.00 (p = .007) for Concentration/Distractibility. (Table 4).
Cognitive-motor training interventions in daily living have been shown to be effective in the maintenance and improvement of executive function in older adults (Wollesen et al., 2020). When presented with a dual task requiring concentration and body movement (e.g., dual-task walking) that involves attention and executive function (i.e., when presented with tasks to be performed sequentially), the prefrontal cortex is activated and cerebral blood flow is improved. Therefore, it appears that a dual task in a horticultural therapy program that is performed in stages is more effective in improving cognitive function than a single task (Doi et al., 2013). When a cognitive task is novel, the frontal cortex (FC) is activated; when the cognitive task is familiarized, FC activation decreases; then, when a similar but different cognitive task is presented, the FC is slightly activated again (Raichle et al., 1994). This is consistent with the finding that there was a positive effect in the Go/No-Go task in this study, where subjects were given two instructions and asked to perform a finger movement under one instruction (Go) and inhibit it under the other (No-Go).
It seems that the selection of appropriate cognitive interventions is important for the effectiveness of horticultural therapy programs. Unlike previous studies, this study focused on the selection of cognitive interventions for each sub-item, in addition to the cognitive function (the therapeutic purpose) of the subjects, which were applied in stages to all activities. This study is limited by the small number of subjects and the short duration of the programs, which makes it difficult to generalize the results. To expect sustainable effects, it seems necessary to conduct further or follow-up studies after a certain period of time. There are limitations to the study of older adults with dementia, but considering the educational background, age group and differences in cognitive function of the subjects, as well as horticultural therapy programs, it seems that specific research is needed from a neurological perspective, along with the use of survey tools that help improve cognitive function.
Conclusion
This study was conducted once a week for a total of 8 sessions to examine the effect of a horticultural therapy program on the cognitive function of older adults with dementia (OAD) in a daycare center. The subjects were a total of 27 OAD using the K Daycare Center in G City, with 10 and 17 in the control and experimental groups, respectively. In this study, therapeutic interventions were applied to each of the detailed items to activate the frontal lobe function of OAD, including Go/No-Go, Digit Span, Word Fluency, and Concentration/Distractibility. They were evaluated before and after the program to examine the differences. The control group showed no significant differences in Go/No-Go (p = . 132), Digit Span (p = .257), Word Fluency (p= .062), and Concentration/Distractibility (p = .180) before and after the implementation of the horticultural therapy program. However, the experimental group showed statistically significant, positive differences in Go/No-Go (p = .001), Digit Span (p = .001), Word Fluency (p = . 038), and Concentration/Distractibility (p = . 007). In particular, since there was a significant difference between the groups on the Go/No-Go item in the post-test (p = .001), horticultural therapy appeared to be valuable as a program that trains OAD to respond immediately to presented signals. Therefore, it is suggested that a horticultural therapy program has a positive effect on frontal lobe function among the cognitive function domains, and that horticultural therapy is effective as a cognitive intervention program. The analysis of cognitive function in OAD is considered an important process that allows the prediction of potential intervention techniques.
Notes
This work was supported by research funds from Daegu Catholic University in 2023.