Dementia is associated with cognitive decline as well as behavioural and psychological symptoms (BPSD). Agitation (e.g. pacing and calling out) is the most commonly exhibited symptom in older adults with dementia [1, 2]. The prevalence of agitated behaviours amongst persons with dementia in nursing homes is 48-82% . These challenging behaviours are stressful to carers and difficult to treat. Behaviours stemming from pain, major depression or psychosis benefit from treatment with analgesics, antidepressants or antipsychotics. In other cases, psychotropic medications have limited efficacy but are widely used . Some pharmacological interventions are reported to precipitate agitation in nursing home populations [5–7] and can have adverse effects including confusion, somnolence, gait abnormalities and falls . Therefore, increasingly more attention has been paid to nonpharmacological interventions which are associated with fewer risks .
Three psychologically-oriented paradigms have emerged to explain BPSD and to generate testable interventions. Learning theory asserts that behaviours are reinforced when carers reward them with attention. Calling out, for example, increases in frequency if nursing staff attend to residents when they are noisy but otherwise ignore them . In the unmet needs paradigm, inappropriate behaviours stem from normal human needs - physical, emotional and social - that carers fail to perceive and address . Needs for social interaction and physical movement, for example, might be addressed by carefully selected group activities and exercise. According to the stress threshold model, dementia reduces the capacity to cope with stress, resulting in inappropriate behaviours . Stress levels can be modulated to tolerable levels by attending to signals of distress and alternating periods of rest and activity. In reality, most psychosocial treatments blend elements of all three paradigms.
Recent reviews and meta-analysis [13–15] showed that sensory interventions (e.g. aromatherapy and hand massage), one-to-one social interaction, individualised music, recreation therapy and family videotapes reduced BPSD more compared to conditions offering an equivalent level of social interaction in a small number of robustly designed studies with moderate to strong quality ratings and adequate statistical precision [14, 15]. The largest effect sizes were found in studies of treatments that could be tailored to participants' backgrounds, interests and skills. For example, music that participants had enjoyed earlier in life reduced agitation better than standard classical music  while audiotapes of a family member's voice worked better than a stranger's voice . A few treatment effect sizes reached 0.7, exceeding those of most psychotropic medications [14, 15]. The calibre of research was generally low, however, and only 17 of 37 carefully selected studies from a total of 176 had "positive" results. Most studies were flawed by low symptom counts, unreliable behaviour ratings, small sample size and limited time-frames. Few of them controlled for the benefits of the one-to-one interaction that underpins most psychosocial treatments. Agitation can respond well to real, and even simulated, personal contact [17, 18] making control conditions providing equivalent social attention, interaction and diversion desirable.
Taking these limitations in account there still is evidence that one-to-one interaction with a diversional or ADL focus outperforms baseline or "usual care" conditions in reducing agitation and improving affect. Activities based on Montessori principles might perform even better. A recent study using a Montessori-based activities program (including 5 pre-selected categories of activities) showed that the Montessori program resulted in improvement in aggressive and physically non-aggressive behaviours, an increase of positive affect and fewer difficulties in providing care compared to a "presence"-condition .
Montessori-based activities derive from the principles espoused by Maria Montessori and subsequent educational theorists to promote engagement in learning, namely task breakdown, guided repetition, progression in difficulty from simple to complex, and the careful matching of demands to levels of competence [20, 21]. With respect to dementia, Montessori activities provide socialisation, meaningful activity and diversion through the medium of one-to-one interaction, in line with Cohen-Mansfield's theory of unmet need , and they can easily be adapted to the interests and skills of people with dementia. Activities are designed to tap procedural memory which is better preserved than verbal memory while minimising language demands and providing external cues to compensate for cognitive deficits. Familiar objects provide cues to their own use (e.g. playing cards suggest sorting them in a sequence) and tasks are demonstrated by a facilitator who then hands the object to participants, thus prompting them to follow suit.
The current study explores the effect of personalised one-to-one interaction based on Montessori principles on BPSD in residents in aged care facilities compared to a plausible control condition, which controls for the benefits of the one-to-one interaction that accompanies the Montessori intervention. To this end, we will conduct a controlled trial with randomised cross-over between conditions to test the hypothesis that individualised, goal-directed activities reduce the frequency of behavioural symptoms of dementia significantly and increase positive affect and engagement more than a relevant control condition.