A total of six publications were included in this review. The study selection process is shown in Fig. 1. The six publications are underpinned by the following intervention types: two equine assisted therapy interventions [26, 27], one equine-assisted activities program intervention [28, 29], and one adaptive riding intervention [30, 31]. Of these six publications, two relate to the same study [28, 29].

PRISMA diagram of the study selection process

The results of the methodological quality assessment of the included publications are reported in Table 1. Four publications were of medium to high quality [26,27,28, 31] and two were high quality [29, 30].

Study characteristics are provided in Table 2. Five studies were from the USA [27,28,29,30,31] and one from Brazil [26]. All the included studies were published between 2018 and 2022, except for one study which was published in 2014 [27]. In relation to study design, four were quantitative [26,27,28, 31] and two were qualitative [29, 30]. Borges de Araujo et al. [26] utilized a quasi-experimental, uncontrolled pre-post design, whilst Fields et al. published quantitative [28] and qualitative [29] data from a mixed-methods case-study. The remaining studies utilised a randomised pre-post crossover study [27], a descriptive case study [31], and a qualitative case study design [30]. Sample sizes were small and ranged from 5 participants [29, 30] to 16 participants [27]. Non-random convenience sampling was used for all studies.

Participants from four studies were people diagnosed with mild to moderate dementia or Alzheimer’s disease and were recruited from an adult day services centre [27], a long-term care facility [28], unspecified local organisations [31], and a local referral centre for people living with dementia [26]. One study explored the impact of an equine-assisted intervention from the providers perspective [29] and another from the dementia care partners perspective [30]. The mean age of participants living with dementia ranged from 70 years [30] to 83.3 [28]. The mean age for dementia care partners was 58 years [30].

The equine-assisted services examined in this review used horses [26,27,28,29,30,31], donkeys [30, 31] and a pony [28, 29]. Four studies conducted the equine-assisted service at an accredited therapeutic riding centre (Professional Association of Therapeutic Horsemanship International), and two studies used therapy horses that had docile temperaments and were used exclusively as therapy animals [26], and in therapeutic riding programs for children and teenagers diagnosed with autism and mental health conditions [27]. Only one study provided the characteristics of the horses used in their study [27].

The duration of equine-assisted services varied for each study: the longest consisted of 20 half-hour sessions of equine-assisted therapy, twice a week for 10 weeks [26]. The shortest comprised one session a week, of three 15-minute activities per session, for four weeks [27]. Two interventions consisted of weekly one-hour sessions for eight weeks [28,29,30,31]. The intervention activities were varied: one intervention encompassed horse riding [26], two offered a choice of riding or ground activities (grooming, petting, and observing) [28, 30, 31], and one was a non-riding intervention offering ground activities of grooming, observation, horse care, horse exercise, and horse painting [27]. Lassell et al. [31] was the only study to investigate the impact of two different interventions (adaptive riding and adaptive gardening). Fields et al. [28] and Fields et al. [29] investigated the impact of an Equine-Assisted Activities Program, compared to the control of participating in long-term care regular activities of downtime, snack and mealtime, TV, games, physical therapy, and joke/riddle time. Similarly, a crossover design was utilised to establish the impact of participating in an equine-assisted therapy intervention, compared to the control of participating in regular adult day service activities [27].

Two interventions assessed cognitive and behavioural outcomes through the QoL indicators of time use and participation (gaze, position and movement, communication, and active participation) and emotional well-being (apparent affect and agitation) [28, 31]. Both studies used the Activity in Context and Time [28, 31] to measure outcomes. The Activity in Context and Time is a quantitative, computer-assisted tool that measures the activities, time-use patterns, and QoL indicators of people living with dementia in aged-care facilities or other care institutions [32].

Dabelko-Schoeny et al. [27] investigated the impact of participating in equine-assisted therapy on physiological and behavioural outcomes. The physiological outcome of stress was measured via salivary cortisol concentrations of participants, pre- and post-intervention. Behavioural outcomes were assessed using [1] a modified version of the Nursing Home Behaviour Problem Scale [33] to measure disruptive behaviour, and [2] the Philadelphia Geriatric Center Affect Rating Scale [34] to measure behaviour and affect [27]. The Nursing Home Behaviour Problem Scale was developed by Ray et al. [33] and is a 5-point Likert-type scale of 29 items representing common observable disruptive behaviours demonstrated by people living with dementia in nursing homes [33]. The Nursing Home Behaviour Problem Scale used in the study by Dabelko-Schoeny et al. [27] was reduced to 22-items and modified to included questions pertinent to the study population from an adult day centre [27]. Affect was measured using the Philadelphia Geriatric Center Affect Rating Scale, developed by Lawton et al. [34], and recorded observed expressions of sadness, anger, pleasure, anxiety/fear, or interest [27, 34].

Only one study [26] examined physical outcomes, through the assessment of balance (force plate) and functional mobility of participants (Timed Up and Go test and 30-second chair stand test). Balance was measured using the AccuSway Plus force plate from Advanced Mechanical Technology and Balance Clinic software; data was collected according to Mann et al. [35] and Teixeira et al. [36]. The Timed Up and Go test is used to identify elderly people at risk of falls [37] and measures the time taken to stand up from a chair, walk three metres, and return to sit in the same chair [26]. The 30-second chair stand test is a measure of leg strength and is measured by the number of times an individual can sit and stand from a chair in 30 s [38]. Cognitive changes were measured in verbal fluency, and cognitive function via the Mini-Mental State Examination [39]. All outcomes were measured pre- and post-intervention.

Two studies investigated equine-assisted services from a perspective other than the person living with dementia [29, 30]. Lassell et al. [30] investigated well-being, meaning through social connection and functions in daily life of people living with dementia from their carer’s perspectives, whilst Fields et al. [29] examined the safety, acceptability and QoL outcomes for participants from the perspective of providers of the Equine-Assisted Activities Program [29]. Care partners of people living with dementia participated in face-to-face semi-structured interviews within 1–2 weeks of the intervention and discussed outcomes of the intervention for themselves and for people living with dementia [30]. Field notes detailing observations of the date, time, setting, events/activities and reactions of the participants, were guided by Glesne [40] and triangulated with interview data [30]. Similarly, face-to-face semi-structured interviews were conducted immediately after the conclusion of the Equine-Assisted Activities Program to explore providers perspectives of the intervention on QoL of long-term care residents with dementia [29]. The qualitative process of coding the interview data was guided by Neergaard et al. [41].

All included studies found a favourable impact of participating in equine-assisted services. Studies confirmed that participating in equine-assisted services had positive effects on social [28, 30, 31], emotional [27, 28, 30, 31], and behavioural [27] outcomes for people living with dementia, as well as improved physical health [26]. Where the two interventions of riding and gardening were compared [31], participants expressed positive QoL indicators for the domains of apparent affect (interest and pleasure) and participation (engaged gaze, communication, and active participation) for both interventions. However, complex active participation was observed for adaptive riding but not for adaptive gardening [31]; that is, riding participants engaged in two or more activities simultaneously (such as riding and petting the horse) whilst gardening participants participated in only one activity at a time (such as planting or weeding) [31]. Moreover, there were increased observations of pleasure and active participation for riding compared to gardening [31]. Negative QoL indicators for apparent affect (sadness, depression, anger or agitation) were not observed amongst parti