Benefits of Music Therapy in the Cognitive Impairments of Alzheimer’s-Type Dementia: A Systematic Review

Background/Objective: Alzheimer’s disease is a condition that can cause memory, thinking, and behaviour impairments. This type of dementia affects approximately 50 million people globally. Currently, there is no remedy for this disease, but there are different treatment approaches, both pharmacological and non-pharmacological, that try to alleviate the symptoms. The remarkable fact about Alzheimer’s response to music is that musical abilities can be preserved even though language could be lost. The objective of this systematic review is to assess the benefits of music therapy on cognitive impairments in older adults with Alzheimer’s disease. Methods: This is a systematic review carried out following the PRISMA guidelines. The literature searches were conducted in the following databases: PubMed, SCOPUS, Cochrane Library, and Dialnet. The inclusion criteria established were as follows: randomised controlled studies and clinical trials published in English and Spanish from 2010 to 2024, patients diagnosed with dementia of the Alzheimer’s type, aged 65 years or older, who had participated in music interventions and had cognitive changes. Results: Eleven studies were included in this review. They showed that music therapy interventions mainly improved memory, language, and orientation. The results of a methodological quality analysis showed that six of the articles had good methodological quality and four had excellent methodological quality. Conclusions: The results of this review suggest that treatment with music therapy improves cognitive impairments in patients with Alzheimer’s disease. In addition, we can be sure that music creates a link between the patient and the specialist.


Introduction
Dementia is a group of disorders characterised by a deterioration of the cognitive level, affecting activities of daily living and social functioning.It is one of the leading causes of disability and dependence in older people worldwide.In addition, it has a significant impact not only on those directly affected but also on their caregivers, families, and communities, as well as on society [1].
Around 5-8% of the population over 60 years of age suffers from dementia at some point in their lives.Moreover, it is estimated that by 2030, 82 million people will have some form of dementia [2].In particular, about 60-70% of the population with dementia suffers from the Alzheimer's disease type [1].
Alzheimer's disease is a slowly and progressively degenerative disease that affects memory and mental functioning, but it can also lead to other problems such as confusion, mood swings, and disorientation in time and space.Usually, this condition and its symptoms worsen slowly over time until they are so severe that they interfere with the daily life of the person [3].It is one of the most disabling and dependence-causing diseases among older people in the world [1].
Old age is considered the main risk factor for developing Alzheimer's disease.The largest percentage of the population suffering from the disease is 65 years old and over.Ninety per cent of this age group and about one-third of the population over 85 years of age suffer from Alzheimer's disease [4].
Although there is currently no curative treatment or treatment that can reverse the progression of the disease, numerous interventions are available to improve the lives of both people with dementia and their carers.Non-pharmacological therapies include psychostimulation, cognitive stimulation, reminiscence, art therapy, reality orientation, sensory stimulation, animal therapy, physical exercise, and psychomotor therapy [5].In addition, music therapy is also included in this type of treatment approach.According to the Word Federation of Music Therapy (WFMT), music therapy is the "professional use of music and its elements (harmony, rhythm, and melody) as a form of intervention in the medical, educational and everyday environment with individuals, groups, families or communities, seeking to optimise their quality of life and improve their health and physical, social, communicative, emotional, intellectual and spiritual well-being".This approach uses sound, music, movement, and body-sound instruments to develop, produce, and generate a bond or relationship between the music therapist and the patient in order to favour the recovery or rehabilitation process [6].
Human beings have musical abilities of their own, so anyone can benefit from a music therapy process.Even if a person suffers from Alzheimer's disease, musical abilities are intact.Music therapy interventions in Alzheimer's disease focus on physical, cognitive, social, and emotional areas [7].Thanks to the cognitive activation generated through music, all higher functions are stimulated.This enables those functions that are preserved to be stimulated with the objective of lasting as long as possible.Music therapy also works on both verbal and non-verbal communication through the imitation of movements and expressions of gestures.In addition, ideational and ideomotor praxias are stimulated through dance and the use of musical instruments and visual and auditory perception by locating and responding to stimuli, among others [7].
The aim of this review is to assess the benefits of music therapy on cognitive impairments in older people with Alzheimer's disease.

Study Design and Search Strategy
This systematic review was conducted according to the PRISMA statements and guidelines [8].
A literature review was conducted during the month of February 2024.The search strategy was established in order to analyse the benefits of music therapy on cognitive impairment in older adults with Alzheimer's disease under study and to update the scientific evidence available in the literature on this subject in recent years.
The following databases were used for the search: PubMed, SCOPUS, Cochrane Library, and Dialnet.The search strategies used were as follows: "cognitive dysfunction", "Alzheimer", and "music therapy" translated into Spanish in those databases that required it.The strategies used in each database are shown in Table 1.
The bibliographic references of the studies of interest were manually searched to identify other eligible trials.In line with this approach, four additional studies were included in the analysis.

Eligibility Criteria
The criteria selection was established following the PICO model (population, intervention, control, and outcome).The inclusion criteria were as follows: The exclusion criteria were as follows: -Publications older than 14 years.-Literature reviews and publications that were not clinical trials.

Study Selection
The pre-selection of the studies was made considering the proposed object of study.Once the search for studies was performed and filters were applied, the researchers reviewed all the titles and abstracts of the identified studies in order to establish their eligibility and inclusion in this systematic review.
The articles that met the inclusion criteria were analysed in detail.The data obtained from the studies included in the review (objective, intervention, duration, variables, assessment tools, and results) were compiled in a table.In addition, the methodological quality of the studies was assessed, and the related data were collected.
All potential full-text articles were independently retrieved and evaluated by two reviewers.The level of agreement between the two reviewers was not specifically calculated.However, any disagreement on the inclusion or exclusion of the full-text articles was discussed and resolved.

Methodological Quality Analysis
The methodological quality of the studies included in this review was assessed with the "PEDro" scale [9].In 1998, Verhagen developed the PEDro scale to evaluate the methodological quality and possible bias of clinical trials.Although 11 items conform to the scale, the first item is not considered in the total score as it relates to the external validity.
The score ranges from 0 to 10 as each item gets a point if the study meets the criteria for methodological quality.The total score is interpreted in such a way that 10 points indicate an excellent methodological quality, scores from 6 to 8 indicate a good methodological quality, scores between 4 and 5 points correlate to a medium quality, and fewer than 4 points show a low methodological quality.

Results
The search in all databases obtained a total of 488 potential studies to be included in this review.Duplicated records and those that did not meet the inclusion criteria were excluded, leaving a total of seven studies included in this review.A total of four articles were obtained from the manual search and included in the review process, leaving a total of 11 studies.The study selection process is shown in the PRISMA flow diagram (Figure 1).The characteristics of the studies included in this review can be found in Table 2, titled studies included in the review.

Cognitive Function Addressed in the Studies
The clinical trials included in this systematic review aimed to offer a wide range of therapeutic approaches for music therapy in the cognitive approach to Alzheimer's disease.In particular, two of the included studies focused on the following very specific aspect of cognition: memory.Simmons-Stern et al. [17] aimed to determine whether the benefit of music mnemonics on basic letter recognition in Alzheimer's disease patients can be extended to content memory.They wrote letters related to common instrumental activities of daily living.In addition, they first selected forty objects related to instrumental activities of daily living together with two actions commonly related to that object.Subsequently, an excerpt from an original nursery rhyme was associated with it, and the lyrics were modified according to the new content to be memorised.In addition, Moltrasio et al. [19] also focused on memory as an object of study, specifically on determining the effect of activating and relaxing music on visual episodic memory in patients with Alzheimer's dementia.In the experimental group, the participants were presented with 36 images that could evoke different degrees of activation, and after a week, they were given an activating, relaxing, or white noise music treatment.After the music exposure, they had to say which images they remembered, by means of a brief description, followed by a recognition task.
Another study that addressed a very specific area is that conducted by Arroyo-Anlló et al. [18].Their study focused on the effects of music on self-awareness and the subject's capacity to understand his/her own states of consciousness.Self-consciousness includes the awareness of one's own mental states, such as perceptions, attitudes, opinions, and intentions to act.
Gómez Gallego et al. [10,15] and Jihui et al. [13] analysed the effects of music therapy on global cognitive functioning, mental state, and neuropsychological aspects.In addition, one of the articles included in this review, Särkämö et al. [16], focused on caregivers.Their study aimed to assess the efficacy of the use of musical intervention on relatives and carers.Also, two studies comparing the effects of active and receptive music therapy were found in this review, including Särkämö et al. [12] and Gómez Gallego et al. [10,15].In addition to those authors who attempted to compare the effects of music therapy with respect to other therapies, we can highlight Innes et al. [11], who compared music therapy with a Kirtan Kriya (KK) Meditation programme, Giovagnoli et al. [14], who compared it with a cognitive training programme, and Chéour et al. [20], who were the only ones to compare it with a motor programme, both individually and combined with a music therapy programme.

Music Therapy Techniques
Analysing the most commonly used music therapy techniques, we found that the use of singing was very frequent in experimental groups.A total of four articles in this review used this technique [12,13,16,17] with a repertoire of songs known and selected by the participants or family members as part of their musical preferences.In particular, Sakamoto et al. [12] and Särkämö et al. [16] accompanied this technique with movement, either dancing or clapping and moving.Nonetheless, Jihui et al. [13] only used the singing of familiar songs and Simmons-Stern et al. [17] used children's songs.Only the study conducted by Giovagnoli et al. [14] used active techniques with a non-verbal approach with free interactions of sound and music using rhythmic and melodic instruments.
On the other hand, we also found studies that used singing, but within a structured music therapy session.In the study by Gómez Gallego and Gómez García [10], each session of the experimental group included several activities as follows: welcome song (patients had to greet and introduce themselves), rhythmic accompaniment activities with clapping and musical instruments (triangles, tambourines, and maracas), movements with background music (several songs were selected and instructions were given to patients to move their upper and lower limbs according to their rhythm and, once a week, dance therapy with hoops and balls was performed), games of recognition of songs and performers (musical bingo was played, and once a week, song recognition was assessed through drawing), and a farewell song (patients were asked to say goodbye).In addition, the second article included in this review, which also used a structured approach, used a welcome song, rhythmic exercises, dance exercises, a music questionnaire, and a farewell song [15].
As for more receptive or passive techniques, the use of music playback was used in experimental groups [11,[18][19][20] and control groups [12,15,16].Arroyo-Anlló et al. [18] and Chéour et al. [20] were the only ones that used music selected by the participants to be listened to.However, Innes et al. [11] and Moltrasio et al. [19] used CDs of music already set by them with instrumental music (Mozart, Bach, Vivaldi, Beethoven, Pachelbel, and Debussy) and classical music (Haydn Joseph's Symphony No. 70, D major, and Pachelbel's Canon in D major), respectively.

Treatment Provider and Type of Participants
Regarding the professionals who applied music therapy, we found seven articles in this review in which qualified music therapists [10,[12][13][14][15][16]20] conducted the experimental intervention.These studies coincide as they used music therapy with structured sessions [10,15] and with active music therapy techniques such as singing, playing instruments, and rhythmic activities [12][13][14]16].Studies where the professional applying the music therapy intervention was not specified coincide with those using passive music therapy techniques such as listening to music [11,[17][18][19].
All participants of the articles selected for this review were at a mild to moderate stage of dementia [10,11,[13][14][15][17][18][19][20], except for those in the study led by Sakamoto et al. [12], who were at a severe stage, and those in the study by Särkämö et al. [16], in which the intervention was performed on caregivers.

Effects of the Intervention
Focusing on the effects on cognitive functions, we found that the application of active music therapy techniques improved cognition in general [10,15,18,20] and showed improvements specifically in verbal fluency [10,13], orientation [10,16], and memory [10,13,16,17,19,20].It also helped to reduce the behavioural problems of dementia [10,12,15] and improve the level of functionality [15] and mood [12,14,16].In contrast, more passive activities such as listening to music helped to maintain cognitive functioning [18] and improve emotional and psychological well-being [11].

Methodological Quality Assessment
The scores obtained on the PEDro scale in the analysis of the studies selected for this review are shown in Table 3.After an exhaustive reading of the 11 studies, it could be observed that the scores were in a range with a maximum value of 10 and a minimum of 6 points.The results of the scale showed that six of the articles have a good methodological quality [10][11][12][17][18][19][20] and four have an excellent methodological quality, which are studies [13][14][15][16].

Discussion
Numerous studies have been carried out with the aim of assessing the efficacy of treatments in older adults with Alzheimer's disease.However, so far, only a few have been published with the aim of evaluating the benefits of music therapy as a non-pharmacological therapy for older adults with Alzheimer's disease.In terms of the objective of this review, there are few clinical trials and RCTs that attempted to test the effects of music therapy on cognitive impairments in people with Alzheimer's disease.
Music therapy is a young scientific discipline with a broad object of study, which has grown from medicine and later also from psychology and musical pedagogy [21].Therefore, the limitation of this study, which made it difficult to carry out this review, is the insufficiency of scientific articles related to the cognitive benefits of music therapy as a non-pharmacological therapy.This may be related to the slow inclusion of this discipline in the field of health.
In almost all the studies analysed in this review, the sample was very small, so the results from these interventions cannot be generalised to the entire population with Alzheimer's disease.However, it will help us to continue progressing in the study of this type of non-pharmacological therapy.
Changes in cognition need a certain amount of time to occur [22].After an exhaustive examination of all the studies included in this review, we observed that most of the interventions have a short duration (approximately 3 months), and few sessions were carried out (an average of 10/12 sessions).Most of the analysed studies obtained significant improvements except for two of them [18,19], whose intervention period was 3 months and two weeks, respectively, and whose conducted sessions were approximately 5 to 7 min.However, one of the studies in which significant improvements were obtained was the study by Jihui et al. [13], which was carried out for six months with two daily sessions of 30-40 min per session, and all the variables studied were improved except for activities of daily living.This suggests that to obtain better results, it would be necessary to apply this type of intervention daily or with longer sessions.This claim is supported by the fact that the studies analysed that did not achieve improvements conducted short sessions during a short period of time.
Regarding the techniques most commonly used in music therapy, we can divide them into passive receptive techniques (the patient's level of participation is lower) and active or expressive techniques (the patient actively participates in the session) [23].Music therapy also uses techniques related to sound and body, and the techniques can be divided into the following [24]: Musical improvisation: Musical improvisation allows the patient to explore aspects of him/herself and aspects in relation to others.It can be vocal, instrumental and/or corporal.It allows the patient to get to know his inner world and to relate to his environment.
Music and movement: Music and movement allow the patient to express himself through his body, connecting his inner world with his environment.
Song: Singing is the union of musical, physical, and social activity, giving rise to a social, motivational, and playful activity.
Musical listening: Musical listening is a technique that facilitates the expression of emotions, concentration, and memory.
Rhythm and percussion: Rhythm and percussion tone and modulate the internal rhythms of the body and improve coordination, motivation, interpersonal relationships. . .With regard to techniques, two of the studies analysed in this review used active techniques of music therapy (singing, playing instruments, clapping. ..) [14,17] and two others were based on passive music listening [11,[18][19][20].In addition, the two types of techniques were combined in the same session in six studies [10,12,13,15,16].This aspect leads us to believe that this last approach is the best treatment option and the one most frequently chosen in the available research on this subject.The studies included that used the approach with mixed techniques obtained better results in the variables studied, the most favoured being orientation and memory and, to a lesser extent, language.
The use of familiar music makes users relate to their sound identity.Although one of the included studies [13] that used this type of music did not show significant results in cognitive or language function, there was evidence of the positive effect on immediate attention span, delayed word recall and self-awareness, socialisation, and cognition [18].Music can stimulate emotions, and listening to music has been related to limbic and paralimbic area activation [25].The use of familiar music in the development of interventions may be one of the main factors in stimulating memories from certain moments in patients' lives.
Adapting songs that are familiar to patients can help Alzheimer's patients in advanced stages to talk more, as practising music improves listening and language skills and also helps to promote memories [26].In the studies analysed in our review, this technique was frequently used [12,16,17,20], showing positive effects on the emotional state of patients [12] and function cognitive globally [20].Singing has also been found to have a temporary and short-term benefit on working memory [16] and to reduce false recognition and eliminate the mnemonic benefit of music [17].
Visuo-spatial supports facilitate the understanding of people with difficulties in oral communication [27].In the studies by Giovagnoli et al. [14] and Moltrasio et al. [19], they used verbal support in addition to visuospatial support.In the first of these studies, the results showed that thanks to these supports, social relations improved.Nevertheless, the intervention of neuroeducation and active music therapy and the intervention of cognitive training helped the stabilisation of memory [14].In contrast, the study by Moltrasio et al. [19] did not obtain significant results.This may be because of the small sample size (n = 28) and the short duration of the study (2 weeks).
Meditation can be useful in a clinical setting as it is associated with states of physiological relaxation that can be used to relieve stress, anxiety, and other physical symptoms, as well as being related to producing cognitive changes [28].Specifically, in this review we found that in the study carried out by Innes et al. [11], where a Kirtan Kriya Meditation and a music listening programme were completed, perceived stress was reduced, improving the frequency of forgetfulness and the subjective long-term memory function at 26 weeks.These techniques can be incorporated into those already used in music therapy for Alzheimer's disease patients.
Only one study that combined music therapy with some kind of motor programme was found in this review [20].The authors compared both programmes separately and combined, obtaining good results in global cognitive function, memory, and functional capacities such as step length, walking speed, and distance covered in the Six-Minute Walk Test.The authors advocated the combined use of both interventions rather than the individualised use of both, which opens up a range of possibilities for music therapy in the motor area.
Regarding the methodological quality of the studies, it can be highlighted that six of the articles have a good methodological quality [10][11][12][17][18][19][20] and four have an excellent methodological quality, which are studies [13][14][15][16].According to the results of the scale (Table 3), all the studies complied with most of the criteria related to the study design and intervention except for the blinding of the therapists and patients, which is because of the nature of the treatment.The use of the PEDro scale ensures the control of possible bias and a better analysis of the studies.Therefore, the good quality of the research analysed in this review supports the interpretation of the results.
Within the field of music therapy, it is necessary to distinguish between "music in medicine" and music therapy.In "music in medicine", patients can listen to recorded or live music, and the intervention is punctual and does not form part of any therapeutic process.Its objective is to promote public well-being from a playful perspective, and it is carried out by professional musicians, health professionals, etc.In contrast, music therapy actively involves patients, the intervention is part of the therapeutic process, it is performed by qualified music therapists, and music is the means to an end and patient-professional relationships are established [29].In this sense, it may be considered a limitation of this review that not all the included studies specified the person who carried out the intervention and applied the treatment.Of the 11 articles included in this review, only 7 specified that the professional who was carrying out the experimental intervention was a qualified music therapist [10,[12][13][14][15][16]20].The rest of the studies either did not explain who the practitioner was [11,18,19] or used a non-health professional, such as a musician [17].However, what was demonstrated in our analysis is that when active techniques are used, which require the involvement of a professional, the figure of the music therapist is explicit in all of them [10,[12][13][14][15][16].The effects of the interventions can be extrapolated to music therapy, as defined by the Word Federation of Music Therapy (WFMT) [6].
Future research needs to take this limitation into account in order to be able to specify, with more evidence, the benefits of music therapy in older adults with Alzheimer's disease.This requires that the professionals applying the intervention are music therapists and that this is specified in the methodologies of the studies.

Conclusions
The results of this review suggest that music therapy improves cognitive impairments in patients with Alzheimer's disease.
Although the number of publications focusing on the use of music therapy for the management of cognitive impairment in Alzheimer's disease is increasing, there is still a need for further research in this field in order to improve cognitive impairment in people with this condition.
We can affirm that music creates a communication link between the specialist and the patient, which can improve different cognitive symptoms of Alzheimer's disease.However, it is necessary that this treatment approach is applied by qualified music therapists in order to extrapolate the results of music therapy itself and not to the use of music in the area of medicine.

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Studies published in Spanish or English.-Studies published between 2010 and the present (February 2024).-Clinical trial studies.-Patients diagnosed with Alzheimer's disease, aged 65 years or older, who have suffered changes in cognition and have participated in music interventions.

Table 1 .
Syntax of combined descriptors in the scientific database search.

Table 2 .
Studies included in the review.
The significant improvements in initiative were higher after CT (38.46%) than after AMT (23.08%) and NE (0%).At 3-month follow-up, verbal initiative (p = 0.02) and episodic memory decreased in all patients.Social relationships and mood improved in all three groups but with more entrenchment after AMT and NE (p < 0.001).

Table 3 .
Assessment of the methodological quality of the studies included in this review.