Since Homo sapiens evolved in a natural environment, an intrinsic physiologic and psychological positive reaction to nature has developed that is involved in maintaining the human being's homeostasis. Thus, an automatic and subconscious propensity to react to nature in a positive manner is theorized.⁴⁰ Orians⁴¹ proposed that there is higher attentional response to environmental cues such as trees and natural features associated with landscapes providing sources of food and water.

Most importantly, therapeutic gardens should contain familiar elements that are typical of the region and activities that elders may have participated in at previous stages of their lifetime.

Therapeutic garden design focuses on increasing sensory stimulation by providing assisted living or dementia residents access to the outdoor spaces on a daily basis. Dementia facilities have elaborate structural and electronic devices to prevent residents from eloping and to reduce the risk of injury or death.⁴² Therapeutic gardens provide assisted living or dementia residents a safe environment for exercise, reflection and passing time with other residents, friends or family members. They may also have structured spaces that reduce disorientation.

To stimulate the senses, therapeutic gardens typically include a variety of plants to promote visual, olfactory, and tactile stimulation and to attract birds and butterflies. Also, trees may provide shade, color, seasonal variation, and sound when the leaves rustle in the wind. Walking paths promote movement, encourage contact with plants (all nontoxic and non-injurious), and lead the residents to protected areas for sitting and socializing.⁴³ For the dementia populations, the paths should be continuous with no dead ends to encourage cardiovascular exercise. Vegetables and herbs can be planted to expand visual and tactile experiences and help with improved eating. Some therapeutic gardens include raised planters where the residents can use their hands or simple safe tools for digging and other activities with supervision. Gardens should be designed to stimulate the senses and to encourage older adults to spend time outside in nature. Horticultural therapy may also be used to promote gardening interests both as pastimes and to stimulate function and cognition.⁴⁴ For climates with extended periods of inclement weather, therapeutic gardens may have enclosed perimeter walkways with exits into the garden. Large windows looking out into the garden allow the residents full view of the garden in order to promote positive ideations and to remind them of the presence of the garden.⁴⁵

Therapeutic gardens in residences for the elderly may reduce pain perception. The sensory stimulation of a natural setting has been proposed to reduce the consciousness of unpleasant internal and external stimuli. In a randomized controlled study utilizing murals of nature sights and tapes of nature sounds supplied to patients undergoing bronchoscopy, pain, but not anxiety, was significantly reduced.⁴⁶ It was suggested that such non-intrusive interventions may reduce the need for pharmacologic analgesia while the patient is undergoing painful, invasive procedures. The mechanism of this distraction therapy was not identified.

With aging, the risk of needing rehabilitation for acute and chronic medical problems such as cognitive decline, altered mental status, strokes, heart attacks, and surgical procedures increases. Preliminary studies suggest post trauma and post surgical patients have improved treatment outcomes secondary to greater exposure to natural settings. Ulrich⁴⁷ performed one of the classic studies on the positive effect of passive interaction with garden settings to reduce pain. Post-cholecystectomy patients having a window with a view of nature required fewer high potency analgesics and had shorter hospital stays than patients with windows having a view of a brick wall.

Another measure of the strength of a passive interaction with nature involved the role of sunlight in post cervical and lumbar surgery patients. Walch et al.⁴⁸ found that patients in high sunlight rooms had less perceived stress, utilized fewer analgesic medications and had lower costs for pain medications. Also, there was a trend, although it was not statistically significant (p=0.58), toward reduced perception of pain. In a third passive interaction study, Park⁴⁹ reported that having plants in the hospital room following thyroidectomy, appendectomy and hemorrhoidectomy shortened patients' post operative hospitalization, reduced analgesic use, and reduced pain, anxiety and fatigue when compared to the control group that had no plants in their rooms.

Many patients in horticulture or rehabilitation therapy have attention deficits due to either internal or external negative stimuli secondary to clinical entities such as pain, post-stroke sequelae, head trauma, anxiety, depression or dementia. James⁵⁰ hypothesized that navigation of one's complex external environment is facilitated by two components of attention, voluntary and involuntary. In his attention restoration theory (ART), voluntary attention filters extraneous stimuli when an individual is attempting to concentrate on a specific task. This voluntary attention undergoes fatigue with time and stress. On the other hand, involuntary attention does not incur fatigue and is stimulated by colors, motion, contrasts and the unusual sensory stimuli in garden settings. Consequently, in a natural setting, engaging the involuntary attention may spare voluntary attention fatigue, allowing a more prolonged and higher level of attention. The benefits of improving attention in a garden setting when compared to attention in non-green or traditional rehabilitation settings has been described.^51-54 Elderly with mild cognitive impairment, dementia, post stroke deficits, or chronic pain may have impaired executive control function (ECF) secondary to cerebral and subcortical changes. Decreased ECF is often accompanied by attention deficits.^55-59 In such cases, conserving voluntary attention in garden settings during activity or rehabilitation sessions may be advantageous and may shorten outcome times when compared to results achieved in the traditional non-green inpatient rehabilitation settings.^7,28

Attention deficits may be barriers to cognitive⁶⁰ and functional improvement following brain injury.⁶¹ The benefit of therapeutic measures to improve alertness and sustained attention for post stroke patients has been reported.⁶² Several studies support the ART hypothesis as a component in attention restoration. Herzog et al.⁶³ reported that the perceived restorative effectiveness of natural settings was ranked higher than the perceived restorative effectiveness of sports, entertainment centers and viewing urban settings. Laumann et al.²⁹ tested the hypothesis that exposure to nature stimuli improves attention restoration. They reported that reduced autonomic arousal, when viewing a video with nature scenes, resulted in subjects' improved attention and orienting task performance. Using different screen sizes, De Kort et al.⁵⁴ found that attention restoration improved with a corresponding increased sense of immersion (increasing screen dimensions) when viewing nature scenes. Improved performance on attention measures was also reported for students looking out a window at natural scenes when compared to students looking out a window at man-made landscapes.⁶⁴

In a study of more active outdoor participation, Hartig et al.⁵¹ found a positive correlation between outdoor walking and attention improvement. After 40 minutes of completing a task requiring focused attention, subjects that walked in a wilderness park reported improved mood and decreased errors in proof reading compared to subjects that followed the tasks with a walk in an urban setting or sat in a windowless room listening to music or reading magazines. In another study of attention restoration with pregnant women in their third trimester, Stark⁵² demonstrated that spending two hours a week in nature activities improved concentration and reduced errors. Using a similar protocol, Cimprich et al.⁵³ found that two hours of exposure to a natural environment per week improved women's capacity to direct their attention 19 days after breast cancer surgery when compared to controls.

The brain is the central organ in determining the best response to a level of danger, thus initiating appropriate responses. Physiological and behavioral reactions to stress involve bi-directional communication of the brain with multiple systems, including the endocrine, cardiovascular and immune systems.⁶⁵ A healthy response to acute stress that promotes adaptation is termed allostatic stress. In contrast, a reaction that promotes a state of chronic stress with negative structural remodeling of the hippocampus, amygdala and prefrontal cortex is termed allosteric load.⁶⁶

The fight or flight model of stress described by Hans Selye⁶⁷ begins by activation of the hypothalamic-pituitary axis (HPA) and the sympathetic systems in addition to the limbic-frontal neurocircuitry system of fear.⁶⁸ Such a response is needed to survive and manage threats such as a house fire or assault. Damage to the brain and body occurs when the stress is chronic, resulting in dysregulation of neurobiologic stress mediators. Allostatic load occurs when the mediators of stress are not turned off after the threat has ceased or when they are not turned on in a manner to adequately manage an immediate threat.⁶⁶

For the elderly, the role of chronic stress on the aging brain is particularly important. Loss of hippocampal cells with aging is normative in most cases; however the glucocorticoid hypersecretion syndrome is not. It is suspected that the cytological degeneration of amyloid in the hippocampus and neocortex, including neurofibrillary tangles and neurotic plaques,⁶⁹ in addition to organ aging, combine to accelerate glucocorticoid hypersecretion.⁷⁰ Thus hippocampal damage from a combination of aging, AD and other trauma appears to promote glucocorticoid hypersecretion as illustrated by elevated basal cortisol and dexamethasone (DEX) resistance.^70-73

Elevated cortisol levels appear to play an important role in memory⁷⁴ and affective disorders.⁶⁶ Imaging studies with PET and fMRI of persons with recurrent depression altered patterns of activity and decreased volume of the hippocampus, amygdala and prefrontal regions.^75-77 In major depression, the duration of the symptoms is a stronger predictor of hippocampal volume loss on MRI than is age.^76,78 Based on these and other findings, it appears that prolonged stress with concurrent neurobiologic changes during aging may accelerate the loss of function and cognition with the end result of an earlier need of health care support due to a declining ability to live independently.^57,58,79-81

The neurobiology and physiology of the stress response provide background for the Overload and Arousal Theory of Ulrich and Parsons.¹⁴ They proposed that modern society bombards the human central nervous system (CNS) with excessive noise, movement and complex visual stimuli. These stressors eventually overload long-term neural and endocrine dysfunction leading to functional and cognitive decline. It is thought that an environment with the appropriate ratio between plant abundance and hardscape (man made structures) may reduce the deleterious effects of man-made settings to the human inhabitants. The ratio of nature and hardscape to foster a positive therapeutic result has been debated.⁸² Current opinion is that this ratio needs to be greater than 70% lush garden and less than 30% hardscape to have a clinical advantage.⁸³ Such an environment that includes pleasant smells, colors and shapes of the plants, in addition to less complex visual stimuli, may reduce CNS arousal and reduce short and long term stress. Appropriately designed garden settings may be ideal for experiencing stress modulation^30,32 and thus have an important therapeutic role for the elderly experiencing the stresses of aging with comorbid medical and psychiatric problems.

Garden settings, both viewed and experienced actively, have already been associated with stress reduction in other populations. Parsons et al.⁸⁵ reported that after a mildly stressful event, subjects viewing simulated drives through nature dominated environs had greater stress reduction, as measured by blood pressure and electrodermal activity, than subjects viewing simulated automobile drives through environs replete with man made hardscape. In another study, subjects viewing pleasant rural scenes on the wall while using a treadmill experienced greater blood pressure reduction than subjects viewing unpleasant urban scenes.^26,85 Ulrich et al.⁸⁶ found that persons waiting to donate blood had more reduced stress as measured by blood pressure and pulse rate when viewing nature scenes on TV than did donors viewing urban scenes on TV, regular TV programming or no TV programs. Viewing nature scenes not only lowers sympathetic arousal, it may alter EEG activity. Nakamura and Fujii⁸⁷ reported that viewing pictures of a natural hedge produced a greater ratio of alpha to beta activity on EEG when compared to subjects viewing a picture of a similarly shaped concrete wall.

In more active garden activities, Hartig et al.³¹ found that after undergoing tasks to increase psychophysiological stress, a walk in a garden setting improved performance on a test of attention when compared to group members who walked in an urban setting. Restoration of blood pressure, emotion and attention were all more positively affected for the nature group compared to the urban group. A recent study by Van Den Berg and Custers¹⁷ also involved active participation within gardens. Gardeners whose stress levels had first been deliberately elevated with a difficult task demonstrated significantly lowered salivary cortisol levels and higher self-reported positive mood after 30 minutes of light gardening activities as compared to those who engaged in indoor pleasant reading after the stressful event. Although the relaxing reading did also reduce cortisol levels, this reduction was less than with the gardening, and positive mood showed no increase with the indoor activity. The authors suggest that gardening, as an involved and goal-directed way of interacting with nature, can be valuable in promoting restoration from stress.

Thus, there are numerous studies demonstrating the effect of nature in decreasing sympathetic response and stress. Multiple modalities have been used to measure stress responses, including blood pressure, pulse rate, electrodermal activity, EEG activity, salivary cortisol level and self-reported positive and negative moods. These studies demonstrate the need for more research to determine if there will be a quantitative difference in stress reduction as measured by sympathetic and endocrine responses when the elderly engage in active and passive garden activities compared to similar activities performed in non-garden environments.

Wander gardens are therapeutic gardens designed specifically for the safety and benefit of residents with dementia. For example, all plants are edible, the garden is enclosed to prevent residents from eloping and all paths lead the residents back to entrances. The number of factors critical to understanding the role of wander gardens for dementia patients is myriad.⁶ Namazi and Johnson⁹⁵ stated that decreased inappropriate behaviors expressed within 30 minutes of finding an unlocked door suggested that a sense of freedom may improve the residents' quality of life. Having the option of leaving the indoor residential area for a well designed garden may be useful in reducing agitation and negative behaviors towards other residents and staff. Thus, the question arises: Is there a positive interaction between dementia patients' ambulatory capacities and benefits from the wander garden?

Several studies have suggested that being able to see trees and flowers reduces agitation and aggression and promotes healing.^7,96,102 In a prospective observational study, Detweiler et al.⁴⁸ investigated the effect on dementia resident behaviors by adding a wander garden to an existing dementia facility. In this study, 34 male residents were observed for 12 months before and after opening the wander garden. Behaviors were assessed using the Cohen-Mansfield Agitation Inventory Short Form (CMAI),104 incident reports, as needed medications (PRNs), and surveys of staff and residents' family members. Results showed that the final CMAI scores and number of PRN medications used were lower than baseline values with a trend for residents who used the garden more often to have less agitated behavior. Staff and family members felt that the wander garden decreased inappropriate behaviors, and improved mood and quality of life of the dementia residents.

Retaining a habit of exercise to assist in supporting ambulatory capacity is an important element in preventive health during aging.105 The consequences of visiting a wander garden on monthly agitation levels of a group of elderly veterans diagnosed with dementia was assessed utilizing a growth model within the framework of hierarchical linear modeling.106 The focus was on differences in the ambulatory capacity of the veterans using wheelchairs, merry walkers and those ambulating freely. A sample of 34 veterans residing in a locked ward in a dementia unit was observed for a baseline period and for twelve months after a wander garden was opened in their facility. The findings suggest that while visiting the wander garden helped lower agitation levels in all the dementia patients there was a differential effect based on the patients' ability to walk unassisted versus those in wheelchairs and merry walkers, with freely ambulatory patients benefiting more.106

In the expanding elderly population, over one third of the community dwellers older than 65 years of age will fall, with 50% of these elderly experiencing recurrent falls.107-109 For the elderly in long-term care facilities, falls and fall-related injuries have been reported to be three times higher than for community-dwelling older adults with a mean of 1.5 falls per institutional bed year.110,111 Dementia is an independent risk factor for falls with an increasing incidence as the disease progresses. The yearly estimates of fall prevalence range from 30% in early dementia to 75% for institutionalized residents with advanced dementia.112

Each year the medical costs climb despite the state of the economy.113 The total direct cost of all fall injuries for people 65 and older is expected to increase from greater than $19 billion in 2000 to about $55 in 2020 in the USA.114,115 Excluding physician fees, the average cost for a fall injury in persons aged 72 and older, was approximately $19,440.116 While about 90% of falls do not require medical attention, approximately 10% necessitate medical attention. Moreover, about 5% of the falls needing medical treatment result in fracture.117,118 It is noteworthy that 95% of hip fractures in the elderly are caused by falls. The mortality for hip fractures in nursing home residents is higher than for community residents with hip fractures.119,120

A variety of medications can be employed to treat behavioral disturbances in the elderly with and without dementia. In the residents with dementia, fall risk is often compounded by the side effects of the routine medications employed to treat the comorbid medical problems in addition to those medications prescribed for concurrent depression, agitation, psychosis, anxiety and insomnia.121 The most common classes of medications to treat agitation and behavioral problems in dementia include antipsychotics, antidepressants, anxiolytics and hypnotics.122 Most of these medications contribute to increased fall risk in the elderly.121 Of all medications, psychotropic medications have the highest risk of increasing falls.123-125

There is sparse data regarding the influence of a garden on scheduled medication use and fall risk for dementia unit residents. Risk factors for falls are extensive for the moderate to severe dementia residents, with psychiatric medications one of the most prominent. Detweiler et al.126 examined the complex interaction of falls and scheduled medications in a garden. The questions investigated were whether a garden had a positive effect on fall frequency and severity and whether it reduced the number and doses of scheduled psychiatric medications used to treat dementia unit residents. The 28 residents experienced about a 30% decrease for both the raw number of falls and fall severity scores after the garden opened. The raw number of falls decreased 38.7% for the high garden users compared to 7.9% for the infrequent garden users. There was a significantly decreased need for high dose antipsychotics, whereas there was relatively no change in primary antidepressant, hypnotic and anxiolytic use.126