**1. Introduction**

In 2016, it was estimated that 47 million individuals are living with dementia worldwide, and this figure is projected to increase to 113 million in 30 years. As a result, the public health burden of dementia is anticipated to significantly increase in the coming years [1]. Currently, the World Health Organization is striving to promote dementia prevention and increase dementia awareness by significantly investing in health and welfare and active research into dementia [2]. Furthermore, many countries have implemented national strategies aimed at optimizing dementia management in preparation for the anticipated burden of dementia and its effects on their healthcare system [3]. Dementia patients commonly suffer from behavioral and psychological symptoms of dementia (BPSD) [4]. BPSD include socially inappropriate neurobehavioral symptoms such as mental and emotional symptoms, hyperactivity, and sleep disorders [5]. Depression and agitation are the most common emotional problems that affect dementia patients [4]. The goal of dementia treatment is to manage patients' inappropriate behaviors and psychological symptoms while considering their quality of life (QOL), and active research into cognitive stimulation therapy, a nonpharmacological intervention for dementia, is ongoing [6]. However, previous studies into therapies for dementia have generally focused on their effect on cognitive abilities such as memory, problem-solving ability, and communication skills, and the impact of these therapies on the psychological and social aspects of dementia has been neglected [7]. Recently, many interventions for the treatment of BPSD have received attention [8–10], including animal-assisted interventions [11,12].

Animal-assisted interventions (AAI) are interventions that involve animals. There are various subgroups of AAI, namely animal-assisted activities (AAA), animal-assisted therapies (AAT), and service animal programs (SAP) [13]. These are known to be effective interventions for older people with cognitive impairment, and recent studies have reported that AAI have positive effects on dementia patients [14]. AAA refer to unofficial activities involving animals that meet certain requirements and are characterized by a certain level of flexibility and spontaneity. AAT refer to interventions involving animals that are aimed at improving certain patient outcomes and are incorporated into rehabilitation programs [15]. SAP refers to programs that utilize trained animals to help clients with physical disabilities to overcome functional difficulties in their activities of daily living [16]. These interventions provide joy to patients, increase their motivation, and allow them to rest [17], and patients are able to resolve their unmet physical and emotional needs by being involved in activities related to patients therapeutic goals [18]. In particular, walking a living animal is not only beneficial to dementia patients but also facilitates the rehabilitation of adults who have undergone surgery or have an illness by reacquainting them with ambulation and recovering ambulation speed [19–21]. The first AAI to be developed were found to reduce depression [22], and the ability of AAI to reduce depression and improve QOL in older people with dementia is currently being investigated [11,23–25]. Despite the known benefits of AAI, their use is restricted in some medical environments due to concerns about patients having a fear of animals, possible infection risk, and fright [26].

Recently, pet-robot intervention (PRI) has been proposed as an alternative to AAI. PARO, the most widely studied PRI, is a seal-shaped robot which responds to light, temperature, touch, and posture and monitors the client's emotional changes and health status using sensors [27]. PARO is reported to have various beneficial psychological and social effects such as promoting interaction, reducing stress, and alleviating depression. Furthermore, PRI has similar effects to AAI involving living animals; overcomes the limitations associated with living animals; and has cost, hygiene, and safety benefits [28]. Notably, one study reported that PARO has a positive impact on depression and psychological agitation in older people with dementia and concluded that PARO is a nonpharmacological intervention effective at alleviating neuropsychiatric symptoms [29]. Furthermore, PARO alleviated stress and agitation and reduced the use of antipsychotics and analgesics in older people with dementia [30].

It is well-known that AAI and PRI have beneficial effects on symptoms of dementia [23,30]. In addition, systematic reviews of the effect of AAI or PRI on symptoms of dementia have been performed [31–33]. However, no studies have been conducted into the effects of both AAI and PRI on BPSD. Therefore, the aim of this systemic review and meta-analysis was to investigate the effects of AAI and PRI on BPSD and to present clinical evidence for the application of these interventions.
