The efficacy of cognitive interventions on the performance of instrumental activities of daily living in individuals with mild cognitive impairment or mild dementia: protocol for a systematic review and meta-analysis

Daily activities can be subcategorised as either basic or instrumental activities. Basic daily activities (BADL) are activities that are concerned with taking care of one’s own body and encompass 10 categories: bathing/showering, bowel and bladder management, dressing, eating, feeding, functional mobility, personal device care, personal hygiene and grooming, sexual activity and toilet hygiene [1]. Instrumental activities of daily living are more complex daily activities. They encompass 12 categories: care of others, care of pets, child-rearing, communication management, driving and community mobility, financial management, health management and maintenance, home establishment and management, meal preparation and clean-up, religious observance, safety and emergency maintenance, and shopping [1]. Engagement in these activities is required for people to participate in home and community life.

The ability to complete BADL usually remains intact among those with MCI or mild dementia [2, 3]. Impairment in BADL activities of daily has been shown to manifest after impairments of instrumental activities of daily living (IADL) [4]. There is a positive relationship between cognitive function and performance of IADL [5‐10]. IADL demand more complex neuropsychological processing than BADL and are more susceptible to the subtle deterioration associated with cognitive decline [11]. It has been demonstrated that deterioration in memory and other cognitive functions may result in problems performing IADL, and thus, impact on people’s ability to independently live in the community [12‐14]. For example, de Paula et al. [6] examined the subdomains of memory and executive functioning, finding that episodic memory and executive function correlated with IADL performance in domestic chores, telephone use, meal preparation and laundry (ps < .p5) as well as significantly predicted performance in financial management, shopping, medication management and using transportation (ps < .05). Similar results were found in Cahn-Weiner et al. [15] that memory and executive function were significantly associated with IADL performance (p = .001). Similarly, Farias et al. [16] also revealed that change in executive function was associated with a change in IADL performance (p < .001). Thus, a greater degree of decline in memory and executive function were associated with greater functional decline. A systematic review [17] examining IADL performance of individuals with MCI compared with cognitively healthy individuals and people with dementia found that people with MCI had intermediate functional performance in more complex tasks requiring higher cognitive demand such as telephone use, medication management and keeping appointments between cognitively healthy controls people with mild dementia, particularly.

As part of the normal ageing process, older adults may experience deterioration in cognition in which their cognitive functioning negatively affects their ability to perform IADL [18]. These cognitive changes appear to be greater in individuals with MCI and even more significant in individuals with dementia [17, 19, 20]. MCI and dementia are classified as neurocognitive disorders, whereby there is evidence of an acquired cognitive decline in one or more neurocognitive domains [21]. Deficits may be present in any of the six cognitive domains outlined in the Diagnostic and Statistical Manual of Mental Disorders (DSM-5). These domains are complex attention, executive function, learning and memory, language, perceptual-motor function and social cognition. Cognitive interventions, which address the various cognitive domains, may be vital to maintaining or preventing a decline of cognitive function and subsequent IADL performance in individuals in the pre-clinical or early stages of dementia.

Cognitive interventions include (1) cognitive training, (2) cognitive rehabilitation and (3) cognitive stimulation [22]. These three intervention approaches feature in current literature relating to individuals with MCI and dementia as interventions targeting specific cognitive functions or interventions targeting functional performance in activities including IADL [22, 23].

Cognitive training consists of practising cognitive tasks, focussing on improving cognitive functions in areas such as memory, attention, problem solving and calculation. Cognitive training aims to improve cognitive functions in one or more cognitive domains [22, 24].

Unlike cognitive training, cognitive rehabilitation does not aim to improve cognitive functions specifically. Instead, the aim of cognitive rehabilitation is to address the problems in daily activity performance as a result of the decline in cognitive functions. Cognitive rehabilitation focuses on identifying goals to enhance daily activity performance, providing a tailored intervention for each person. Interventions often include providing compensatory and adaptive strategies and are targeted at improving performance in specific daily activities. Examples of cognitive rehabilitation include memory retrieval techniques, activity or environment modification and errorless learning [22, 25].

Cognitive stimulation is another intervention strategy that promotes engagement in activities to stimulate general cognitive and social functioning in a non-specific manner. Examples of cognitive stimulation include participating in group discussions, book clubs, quizzes and trivia, or music-related activities [24, 25].

A therapy program that utilises a combination of cognitive training, rehabilitation and/or stimulation with individuals with MCI or early stages of dementia may have the greatest benefit because they continue to retain the ability and the cognitive capacity associated with learning and applying new skills [26]. These three cognitive interventions are commonly adopted to assist people living with MCI or dementia as there is currently no proven curative therapy [23, 27]. Therefore, early cognitive intervention becomes vital in maintaining cognitive functions and daily activity performance in older adults.

Due to varying criteria for MCI and the difficulties with diagnosis, it is difficult to determine the prevalence of the disease [28‐30]. A Canadian Health and Aging study reported an estimated population prevalence of 1.03 to 3.02% when adopting different definitions for MCI [29]. The range in prevalence between 3% and 19% was also demonstrated in a population-based epidemiological study [31]. Another review [32] reported prevalence estimates for MCI ranging from 16 to 20%.

Although the exact prevalence of MCI is difficult to determine, it has become widely recognised that the mild cognitive changes associated with MCI are a probable transitional period between normal ageing and a clinical diagnosis of dementia [33‐36]. A study of 133 individuals with MCI and found a conversion rate from MCI to Alzheimer’s disease type dementia to be a staggering 30.5% [37]. According to the World Health Organization, around 50 million people are living with dementia. The total number of people with dementia is expected to increase to 82 million in 2030 and 152 million by 2050 [38]. In 2015, it was estimated that an equivalent value of 1.1% of global gross domestic product would be required to cover the total global societal cost of dementia which was estimated to be USD 818 billion [38]. Mild cognitive impairment, therefore, can constitute a substantial economic burden for public health systems.

With the increasing prevalence of cognitive impairment and dementia in the aging population [39‐42], there is a need to review the efficacy of cognitive interventions to maintain or improve function. To date, reviews have reported the effectiveness of cognitive interventions on cognitive function, particularly on memory. Although individuals with MCI may have preserved functional abilities, it is well established that they may experience subtler difficulties such as making more errors or needing more time than healthy individuals to perform complex IADL. There has not been a systematic review examining the effectiveness of cognitive interventions directly on IADL across the continuum of cognitive decline from MCI to mild dementia. For example, systematic reviews by Simon et al. [25] and Jean et al. [43], both examined the impact of cognitive interventions for MCI on daily activity performance but only as a secondary outcome, and the results on specific IADL were not reported.

This current review will extend previous systematic reviews by including the effectiveness of cognitive interventions on the performance of IADL in all subtypes of MCI and mild dementia. The associated decline in cognition and decreased performance of IADL are not only associated with reduced independence and quality of life [7], but also have far-reaching economic implications and increased health care costs associated that may present challenges to the current health care system [7, 44]. For example, the total direct cost of dementia was $8799 million in Australia and is projected to increase two-fold in 20 years’ time [45]. Most of the direct cost goes to hospitalisation, attending general practitioners and specialists and providing care. Facilitating performance of IADL in people with MCI or mild dementia is an important strategy to aid successful community-based living and reduce the need for additional care and health services. This systematic review and meta-analysis will summarise the available evidence regarding the efficacy of cognitive interventions on the performance of IADL in adults with MCI or mild dementia and highlight areas for further research into cognitive interventions to promote IADL functioning for independent living.

The objectives of this review are to identify, evaluate and synthesise all available randomised controlled trials of cognitive interventions (cognitive training, cognitive rehabilitation and cognitive stimulation) targeted at maintaining or improving IADL performance in older adults with MCI or mild dementia.

A systematic review utilising narrative synthesis and a meta-analytical approach will be conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-analysis (PRISMA) guidelines [46]. The protocol of this systematic review has been registered in PROSPERO (registration number CRD42016042364).

Dementia is an overarching term used to describe a group of diseases associated with an observable decline in cognitive functioning, and individuals living with these conditions often have difficulty with daily activities that affect their independent living. Due to the multiple clinical presentations and underlying etiologies associated with dementia and MCI, there is currently no curative treatment available for the underlying diseases that cause these syndromes [64]. This systematic review and meta-analysis will determine the effectiveness of cognitive interventions in maintaining or improving the performance of IADL in individuals with MCI or mild dementia. It is anticipated that the dissemination of results will inform rehabilitation professionals on the most effective cognitive interventions for clinical practice. It will potentially provide substantial benefit to both people living with MCI or dementia and the health care system by keeping more people living in the community rather than full-time residential care and allowing those in full-time residential care to require less intensive support. Moreover, it can inform and encourage the development of policies and guidelines for the support of these individuals. Results and policy recommendations will be presented at rehabilitation conferences and policy forums. In addition, our description of all recent research in this topic area will identify if and where further research is required.