A Literature Review of the Effect of Animal-Assisted Therapy in Reducing Agitation in Patients with Alzheimer’s Disease

Abstract      

Agitation, such as verbal outbursts and physical aggression, is one of the most challenging symptoms of dementia in patients with Alzheimer’s disease. Non-pharmacological interventions, such as pet therapy, have emerged as a potential treatment for agitation symptoms. This literature review evaluates the application of  pet therapy and its efficacy on mitigating agitation in patients with Alzheimer’s. Synthesizing clinical trials, this paper focuses on the physiological and neurobiological mechanisms through which Animal Assisted Interactions (AAI) can reduce agitated behaviors. Mechanically, this paper explores how through observable decreases in physical stress indicators like pacing and verbal outbursts, as well as increases in measured biomarkers like oxytocin, AAI shows itself as a promising non-pharmacological alternative to treating agitation in patients. That being said, methodological limitations across current literature such as brief intervention timelines highlight the need for larger and highly controlled randomized controlled trials to establish long-term clinical protocols.

Introduction

Alzheimer’s disease (AD) is a progressive neurodegenerative disorder that affects millions of individuals above the age of 40 globally and represents a major public health challenge. When most consider AD, cognitive decline is recognized as the hallmark symptom of the disorder. Despite this, it is often the non-cognitive manifestations—known as Behavioral and Psychological Symptoms of Dementia (BPSD)—that place the greatest burden on caregiving facilities and families of patients (Cerejeira, Lagarto, and Mukaetova-Ladinska 2012). Historically, agitation in AD patients has been managed through psychotropic medications; however, these pharmacological approaches carry significant risks, including sedative side effects and accelerated cognitive decline. Consequently, there is a clinical focus on identifying effective, non-pharmacological interventions (Cerejeira, Lagarto, and Mukaetova-Ladinska 2012).

 Animal-Assisted Interactions (AAI) have emerged as a compelling non-pharmacological therapy for use in geriatric care. AAI uses the human-animal bond to improve emotional, physiological, and social well-being (Filan and Llewellyn-Jones 2006). Therapy animals provide a non-verbal and non-judgmental companion whose contact with patients triggers a release of oxytocin along with a simultaneous decrease in cortisol levels and blood pressure (Kim et al. 2021).

Unfortunately, data on AAI for Alzheimer’s patients is severely hampered by methodological limitations, such as small sample sizes and insufficient follow-up tracking (Filan and Llewellyn-Jones 2006; Yakimicki et al. 2019).

Background

Alzheimer’s disease is a degenerative and irreversible neurological disorder that was first discovered in 1906 by German psychiatrist and neuropathologist Dr. Alois Alzheimer. It began when Dr. Alzheimer examined a middle-aged female patient, August Deter, who was exhibiting extreme and abnormal paranoia, memory loss, and agitation. Unable to prevent Deter’s death, Dr. Alzheimer performed a post-mortem histological examination hoping to find the cause for the observed deterioration of Deter’s physical, cognitive, and behavioral functions. Upon the examination, Dr. Alzheimer discovered the now hallmark signs of Alzheimer’s disease such as amyloid plaques and neurofibrillary tangles of brain fibers (Alzheimer 1907; Graeber and Mehraein 1999). These findings were presented to Dr. Alzheimer’s colleagues and the disease was coined “Alzheimer’s disease” nearly 4 years later in 1910 by Dr. Emil Kraepelin in his textbook Psychiatrie (Kraepelin 1910). At first, Alzheimer’s disease was believed to be a rare condition with an age barrier dictated by Deter who had developed the disease in her fifties (Graeber and Mehraein 1999; Kraepelin 1910). However, around the 1960s and 70s, what was originally thought to be “senile dementia” (cognitive decline that came with age) was found to be pathologically identical to Alzheimer’s disease (Blessed, Tomlinson, and Roth 1968). This discovery led to Alzheimer’s disease and dementia being interchangeable names for this cognitive condition that affects an overall population of around 55 million people worldwide (World Health Organization 2023) including an estimated 7.4 million Americans (Alzheimer’s Association 2024). The disease can show symptoms as early as in the patient’s 40s in rare cases of early-onset. However, most cases see a typical late onset of Alzheimer’s disease on individuals 65 or older (Alzheimer’s Association 2024). These diagnoses were gathered through measuring a patient’s cognitive decline as well as an objective framework based on living biomarkers (Jack et al. 2018). As part of that framework, amyloid-beta testing (brain imaging) and tau pathology testing (blood or cerebrospinal fluid tests) are used to establish the existence of abnormal amyloid plaques and the spread of toxic neurofibrillary tangles, respectively. The presence of these signs and symptoms are required to establish an Alzheimer’s diagnosis (Jack et al. 2018; Hansson et al. 2021).

Pharmacological intervention has been used for many years in an attempt to combat Alzheimer’s disease. Medicinal drugs, while impermanent, hold many benefits for patients (Cummings et al. 2022; Birks and Harvey 2018). Along with boosting neurotransmitters and managing behavior, some medicines can provide a temporary stabilization for Alzheimer’s patients that can help reduce caregiver burnout (Cummings et al. 2022; Birks and Harvey 2018). Even so, pharmacological limitations continued to halt scientists and doctors in developing a cure for Alzheimer’s (Cummings et al. 2022). Furthermore, pharmacological treatment can have adverse side effects such as gastrointestinal (GI) distress and increased risk of falling (Birks and Harvey 2018). Most of all, regular use of Alzheimer’s medication reduces its efficacy over time as more neurons die off (Cummings et al. 2022; Birks and Harvey 2018). As a result, modern medicine bifurcated its approach to the disease into two distinct focuses (Winblad et al. 2016). One track being long-term prevention and early detection of Alzheimer’s and the other being a focus on the management and comfort of patients already suffering from the disease (Winblad et al. 2016). With how progressive Alzheimer’s disease is, it became important to identify the warning signs of cognitive impairment before it developed into a near complete incapability of self-regulation (Jack et al. 2018, 535; Winblad et al. 2016). For those with Alzheimer’s disease, the primary clinical target of dementia care is quality of life (Winblad et al. 2016; Gitlin et al. 2012).

As such, there have been a wide variety of methods attempted ranging from pharmacological interventions to familial and personal caregivers (Gitlin et al. 2012, 2020). And while there are pharmaceutical treatments that manage to slightly slow cognitive decline, they often come with side effects and limited efficacy for behavioral symptoms (Cummings et al. 2022; Birks and Harvey 2018). This has prompted researchers to look for non-pharmacological therapies (Gitlin et al. 2012; Park et al. 2020). One such method that has recently gained more traction is pet therapy or animal assisted therapy (AAI) (Park et al. 2020). Pet therapy has already been proven to be effective in treating general mental health conditions like anxiety and depression (Charry-Sánchez et al. 2018). The presence of an animal companion helps many individuals with such afflictions to feel more grounded and calmer; and in hope of seeing a similar effect in patients with Alzheimer’s disease, pet therapy has gradually been introduced as a possible option for maintaining a reasonably high quality of life for individuals with Alzheimer’s (Park et al. 2020; Charry-Sánchez et al. 2018).

Effect of Pet Therapy on Agitation

The effectiveness of pet therapy in mitigating agitation is rooted in distinct psychological and physiological mechanisms. From a sensory perspective, the experience of stroking an animal’s fur returns the individual to the functions of the parasympathetic nervous system, increasing release of chemicals like acetylcholine and allowing calming hormones like oxytocin to take over. Furthermore, these positive interactions are associated with reduced production of the stress hormone cortisol, which was detected in saliva samples from patients (Sheikh et al., 2021). Additionally, what Sheikh’s literature review found that is especially promising about AAI is the bi-directional aspect that can be seen with pets such as dogs that dynamically react to human emotion — for example, when a dog holds eye contact with a human, or when a dog knows to lean into a person to help them feel accepted by the animal.

Managing the behavioral and psychological symptoms of dementia (BPSD)—particularly agitation, aggression, and late-afternoon distress known as sundowning—presents a profound clinical challenge in Alzheimer’s care for both the caregivers and those with Alzheimer’s. Clinical trials within high-stress medical settings demonstrate that the introduction of a trained therapy dog yields statistically significant, immediate reductions in patient agitation compared to standard care routines (Krüger et al., 2021). Kruger’s study was a systematic review of 51 studies concerning AAI with patients with Alzheimer’s disease. The study found that there was a correlation between animal intervention and a decrease in agitation, while oppositely finding no significant relationship between AAI and depression/quality of life.  Even so, this behavioral shift suggests that the physical presence of an animal provides a grounding, non-threatening stimulus capable of redirecting a patient’s attention away from environmental stressors or internal confusion.

Despite these positive outcomes, a comprehensive analysis of the literature reveals critical methodological limitations regarding the sustainability of these interventions. While the immediate de-escalation of agitation during a pet therapy session is well-documented, evidence tracking the long-term or residual effects after the animal leaves remains scarce and often low-certainty (Park et al. 2020). Park performed a systematic review of 9 randomized controlled trials published between 2000 and 2019. It was found that there is a statistically significant amount of evidence that AAI reduces depression in dementia patients. However, with broader outcomes like sustained agitation reduction and long-term behavioral changes, the overall evidence base was limited by small sample sizes and a lack of follow-up tracking. Additionally, individual patient histories must be considered; for individuals with pre-existing cynophobia (fear of dogs) or animal allergies, the introduction of a therapy animal can inadvertently exacerbate psychological distress rather than soothe it. Consequently, current research positions pet therapy as a highly potent, acute tool for situational agitation management, though further standardized, longitudinal studies are required to determine how to extend these calming effects into a patient’s broader daily routine.

Research Gaps 

Most studies concerning AAI in use for treating stress and agitation in dementia patients all share similar research limitations. Those limitations being that oftentimes the studies lack sufficient sample sizes or long-term follow-up for the realistic viability of using therapy animals in caregiving settings — to address this, prospective longitudinal studies should be conducted. Another variable these studies fail to capture is the maintenance aspect of using therapy animals to help treat dementia patients. The care for the therapy animals adds another layer of work to be done for patients that already require around the clock care. Even if there were to be specific people assigned to taking care of the therapy animals, it would require more people in the caregiving/nursing profession which is already short staffed.

Conclusion

The synthesis of current literature indicates that pet therapy can serve as a valuable non-pharmacological strategy for reducing agitation and behavioral distress in individuals living with Alzheimer’s disease. The presence of therapy animals consistently yields reductions in acute agitation, accompanied by increased positive emotional engagement. The physical presence provided by animals appears to mitigate anxiety without the adverse risks often associated with psychotropic medications.

However, while short-term behavioral benefits during active sessions are well-supported, long-term durability remains questionable. Future research should prioritize larger sample sizes and designs that allow researchers to follow up with patients from the sample long after the end of the initial experiment. In this way, the research on AAI with Alzheimer’s patients can hopefully be expanded and possibly conformed into a standardized protocol in caregiving facilities.

References

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