INTRODUCTION

Health at a Glance 2017, from the Organization for Economic Co-operation and Development (OECD), reports that dementia is one of the leading causes of death. In 2015, it represented 4.5% in women and 2.1% in men. The same study places Portugal in 4th place with 19.9 cases per thousand inhabitants, only surpassed by Germany, Italy and Japan, the latter occupying the top of the table with 23.3 cases per thousand inhabitants, while the OECD average is situated in the 14.8. As average life expectancy increases in Portugal, the number of dementia cases increases, and it is estimated that this number will increase to 31.3 per thousand inhabitants by 2037¹.

Although it mostly affects the elderly, dementia is not a normal consequence of aging. Dementia is a group of disorders that comprise a progressive loss of cognitive functions and affect the dexterity that is necessary for the normal development of activities of daily living (ADL)^2-3 among them, attention, short- and long-term memory, activity and movement planning⁴, which leads to person’s development loss, causing changes in their family and social environment, due to their dependence state⁵.

Alzheimer's disease is the most common form, accounting for about 60-70% of dementia cases. Among the less frequent forms of dementia, we can highlight vascular, mixed, Lewy body and Parkinson's disease dementias, among others⁵.

Thus, Alzheimer's Disease of still unknown cause, leads to neurodegeneration and the consequent (progressive and irreversible) worsening of brain functions, culminating in the total loss of autonomy⁶.

The initial symptoms include memory loss, spatial and temporal disorientation, confusion and problems regarding reasoning and thinking, causing changes in the person's behavior, personality and functional capacity, and hindering the performance of their ADL⁶.

At the moment, there is no treatment to stop the progression of the disease and pharmacological treatment is limited to alleviating the symptoms caused by dementia⁷.

The studies carried out indicate that changes in lifestyles and physical exercise can prevent or delay the onset of dementia^8,9. These data suggest that physical exercise improves neuropsychological functioning, although leisure activities can also bring improvements. Thus, an aerobic physical exercise program can be an adjuvant alternative to maintain and improve these functions⁹.

The Specialist Nurse in Rehabilitation Nursing (SNRN), according to the Regulation of Specific Competences, has the competence to design, implement, evaluate and reformulate motor and cardiorespiratory training programs, depending on the expected results¹⁰ in which the prescription of physical exercise is inserted.

The starting question of this systematic literature review (SLR) is: what are the benefits of physical exercise in people with dementia?

The objective of the SLR is to identify the benefits of physical exercise at the cognitive, sensory and motor levels in people with dementia.

MATERIAL AND METHODS

Among the various types of reviews, SLR is the most used, and is defined “as a systematic, explicit and reproducible method that allows the identification, evaluation and synthesis of studies carried out by researchers, academics and health professionals”^{(11: 47)} in order to reduce biases. It is a method that allows for a rigorous synthesis of all research related to a specific question, thus making it possible to obtain the best evidence, which is why it is considered one of the pillars for evidence-based practice¹¹.

To perform an SLR, seven steps must be taken into account: 1) construction of the research protocol; 2) formulation of the question; 3) research studies; 4) selection and review of studies; 5) critical evaluation of each of the articles; 6) data collection; 7) synthesis of results/data¹¹.

To formulate the research question, we used the recommendations of the Joanna Briggs Institute (JBI)¹² based on the PICO strategy. Each dimension of the PICO contributed to define the inclusion criteria: Population (P) - People with dementia including Alzheimer's Disease as it is a more frequent typology of dementia; Intervention (I) - Physical exercise; Comparison (C) and Results (O) - Benefits of exercise.

This resulted in a research question: “What are the benefits of physical exercise for people with dementia?”.

The descriptors related to each of the components of the PICO strategy were: Dementia; Alzheimer Disease; Physical Exercise; Physical Activity, previously validated in the Health Sciences Descriptors and Medical Subject Headings platform.

The inclusion criteria were defined as: experimental and quasi-experimental primary studies, which address the practice of physical exercise in people with dementia and Alzheimer's disease, published over the last 5 years (2014-2018), in Portuguese, English and Spanish, with free access full text.

The survey was conducted during the months of October and November 2018 through the EBSCOHost electronic database platforms (CINAHL Complete; Cochrane Collection Plus; Nursing & Allied Health Collection: Expanded; MEDLINE® Complete; Library, Information Science & Technology Abstracts; Medic Latina), Virtual Health Library (VHL).

The search was carried out by two people simultaneously, from October 20th to November 24th, 2018, taking into account the following Boolean conjugation with the descriptors in English:

((Physical Exercise) OR (Physical Activity)) AND ((Alzheimer Disease) OR Dementia))

Table 1 describes the process of combining descriptors and keywords for searching the databases. Figure 1 illustrates the PRISMA flowchart corresponding to the identification, analysis, selection and inclusion of articles.

The articles selected for full reading were independently evaluated by two investigators, according to methodological quality criteria proposed by the JBI¹², with only articles with more than 75% of the criteria being selected.

Information was extracted from the articles about authors, year, country, sample, data on modality, intensity, volume, frequency and duration of physical exercise. The classification of the levels of evidence of the included studies was based on the criteria of the Registered Nurses Association of Ontario¹³.

Figure 1 Identification, analysis and selection of articles¹⁴. 

RESULTS

Seven articles were included in this RSL, published in the following years 2015^15,16,17,19, 2016^18,21 and 2017²⁰, the sample of people varied between 30²¹ and 170¹⁵. Regarding the control group, it ranged between 15^16,21 and 116¹⁹. Duration of studies between 8 weeks¹⁸ and 15 months¹⁹. All studies included (Table 2) are experimental primary studies according to the Nurses Association of Ontario with levels of evidence Ib, that is, evidence obtained from at least one controlled study¹³.

DISCUSSION

The analysed studies present a variety of results, namely: cognitive function and memory^16,18-19; balance and risk of falling^15,20-21; mobility ^15-16,19,21; ADL^15-18,21 and role of the caregiver^15-16,19,21; apathy, agitation and depression¹⁹. Regarding the modalities, studies were carried out through muscle strengthening exercise programs^15,20-21, aerobic exercises^17,19-20, combined motor coordination and balance exercises^20-21 (Otago's exercises) ¹⁸, gait²¹, use of pedalboard¹⁶ and static bicycle¹⁹, which encompass different characteristics in terms of frequency, intensity, volume and duration. Otago's Exercise program consists of a set of lower limb muscle strengthening exercises, balance exercises and a walking plan. They are prescribed individually, take about 30 minutes and are performed three times a week, however, walking it is performed at least twice a week, and the progression increases throughout the sessions.²²

The intensity varies between mild^16,19, moderate²⁰ and high¹⁵, despite being little explored in the presented articles. It is observed that the ways of prescribing intensity varied a lot, with seven predictors: Maximum Heart Rate (HRmax); Maximum Oxygen Consumption (VO2max); Resting Heart Rate (FCR); Peak Oxygen Consumption (VO2peak); Thresholds: T1: Anaerobic threshold and T2: Respiratory Compensation Point (CRP); Peak Heart Rate (HRpeak) and Useful Functional Capacity.²³ And, according to the guidelines of the American College of Sports Medicine for Exertion tests and their prescription²⁴_, the intensity should be categorized by cardiorespiratory exercises, resistance exercises, flexibility exercises and neuro-motor exercises, being recommended for the latter, two or three days a week, 20-30 minutes a day and should involve motor skills, namely balance, agility, coordination, training with proprioceptive exercises and multifaceted activities , to improve coordination skills and reduce the risk of falls in the elderly. It recommends aerobic activity with an intensity of 40 to 60% of the reserve heart rate, or 11 to 13 on the Borg scale²⁵. It also states that the duration is related to the intensity of the exercise, thus, a lower intensity should be maintained for a longer period of time and due to the potential risks associated with high intensity exercises, light to moderate intensity with greater duration for the non-athlete adult.

CONCLUSION

The initial goal of this SLR was achieved as evidence is revealed of the beneficial effects of physical exercise on cognition and motor skills in people with dementia.

Thus, we were able to answer the research question and realize that interventions that combine aerobic exercise, strength, endurance, balance and motor coordination are essential interventions to produce improvements in the health and well-being of people with dementia, not only over time, but also when compared to other interventions, such as sedentary social and recreational activities.

Studies have shown significant improvements in areas such as cognition, agitation, mood, mobility and functional capacity. Although the frequency, intensity and volume of the studied exercises vary and even though the optimal parameters have not yet been determined, the analysis of this review concludes that a physical activity program based on aerobic exercises, such as the use of pedalboards at a frequency of 3 to 5 times a week, at an intensity that goes up to 60 to 75% of the reserve heart rate and with a duration of 30 to 50 minutes, it can bring benefits in terms of increased capacity to perform ADL. It is also concluded that a program of high intensity muscle strengthening exercises with emphasis on the lower limbs, with 2 sets of 12 repetitions at a frequency of 2 to 5 times a week can have effects on balance and motor coordination.

In future studies, an activity plan that includes specific exercises with well-defined characteristics shoud be instituted, as well as the possibility of being carried out at home with the training and intervention of caregivers to be taken into account.

Finally, it remains to be recognized that despite the countless knowledge that is already possessed, doubts still remain concerning the physical exercise to be prescribed, namely the duration, volume and intensity needed, and thus extracting the maximum benefits from it for people with dementia. Answering these questions is fundamental for exercise prescription by the SNRN.