Music therapy is a potential intervention for cognition of Alzheimer’s Disease: a mini-review

Alzheimer’s Disease (AD), which is the most common type of dementia, is a neurodegenerative disease characterized by progressive cognitive impairment and neuropsychiatric symptoms [1, 2]. It can cause patients to lose their daily living abilities. The pathological features of AD are accumulated amyloid beta (Aβ) protein in senile plaques and tau protein in neurofibrillary tangles, as well as the loss of neuron and synapse [3]. AD is one of the greatest health challenges of this century for humanity. With the increasing aging population, the numbers of AD and other dementias are growing dramatically. There is a report which says the number of AD patients has reached over 35 million worldwide in 2013, and this number is estimated to triple by 2050 [4]. However, there is lack of effective disease-modifying drugs for AD [5, 6].

Considering the growing population of AD and the severe harmfulness to patients’ health, non-pharmacological treatments play a more and more important role in preventing and relieving symptoms of AD, such as physical exercise, music therapy (MT), diet and so on [7, 8].

MT is an important method for neuropsychological, cognitive, and social behavior goals in the field of dementia with low-cost [9]. It requires that research, practice, education, and clinical training are based on professional standards in MT (World Federation of Music Therapy (WFMT)) [10]. Many researches have demonstrated that MT is beneficial to improve cognition and to reduce neuropsychiatric syndromes of AD [10, 11]. Since the absence of side effects and the convenience to operate for AD patients and their caregivers, MT becomes an ideal option for intervention. In this review, we will refer to recent articles to summarize different techniques, diverse clinical trials, and the mechanisms of MT in impacting cognition in AD patients, thus providing reference for future research.

Music has been reportedly used in the field of dementia for many years [12]. And many different techniques with the sound elements can be observed in different clinical trials and studies. MT is always conducted by a qualified music therapist [10], so that the therapist can mediate the music treatment according to different patients based on the psychological and/or rehabilitative approaches [9]. Because of the wide and heterogeneous range of applications, there might be some direct influence on the results of MT for dementia. So we will summarize different techniques of MT for dementia especially for AD in this paragraph, including listening to the music, singing songs, music-based intervention, background music, music with activities and multisensory stimulation.

Although most articles have indicated that MT has helpful effects for AD, the opinions on the effect of cognition are inconsistent [11]. There are many articles which have found that MT can reduce the mood symptoms and behavior disorders in dementias, especially depression, anxiety and agitation [30‐33]. Yet the number of researches on the cognition topic of MT for dementia is lesser. Recently, scientists have paid more attention on the cognitive effect in AD patients with MT (see Table 1).

Increasing articles have demonstrated that MT can improve multiple domains of cognitions in AD patients, including attention, psychomotor speed, memory, orientation and executive functions [10, 23, 25, 26]. Bruer RA and other scientists found that listening to the music could increase the global cognition of AD [25, 34]. And Ozdemir L pointed out the effect of MT for AD could last for at least 3 weeks after intervention [26]. After 6-week intervention, Gómez Gallego M et al. found that listening to the music which patients like could significantly improve the memory and orientation of AD. At the same time, improvements were observed in depression and anxiety in AD patients. In addition, anxiety was reduced in mild ones, and delirium, hallucinations, agitation, irritability, and language disorders were reduced in moderate AD ones [22]. Kim HJ et al. demonstrated that multi-domain cognitive stimulation including music therapy could improve the word-list recognition and recall test scores. Besides, the domain of community affairs of AD patients and the Quality of Life (QOL)-AD of caregivers were also better [27]. Satoh M et al. indicated that listening and singing could improve psychomotor speed in AD after 6-month treatment. Decreasing Neuropsychiatric Inventory (NPI) score and prolonging sleep time were also observed after MT [10]. The clinical trial conducted by Arroyo-Anlló EM et al. showed that listening to unfamiliar music decreased the scores of MMSE and FAS, whereas the cognitive test scores did not vary in the familiar music group [15]. Which suggest the preventive and protective effects of music therapy in AD process. However, trials above were almost about dementia patients at the mild or moderate stage. AD patients at severe stage might not cooperate with scientists to complete MT trials because of physical or cognitive problems. For example, they might not usually sing [25], or could not take part in the neuropsychological tests, and so on. So there were few studies about the severe AD patients. Narme P et al. compared MT with cooking therapy in moderate or severe AD or mixed dementia patients. Result showed that both music and cooking improved patients’ emotions and ameliorated their behavioral disorders, yet no benefit was on the cognitive status [24].

In addition, Simmons-Stern NR et al. found that compared with spoken lyrics, AD and healthy older adults showed better scores on the memory test of sung general lyric content. However, participants in two groups performed equally on memory tests of specific lyric content both by sung and spoken. This indicated that music could enhance the preferential sensibility to a familiarity-based content rather than increase the recollection of memory process [35]. Palisson J et al. also verified that sung texts were better remembered than spoken texts for both AD and healthy groups, which indicated music during the encoding stage could facilitate learning and retention [19]. Nevertheless, another research conducted by Simmons-Stern NR et al. in 2010 showed that just AD patients had better recognition accuracy for the sung lyrics than the spoken ones, which did not exist in healthy older adults group [18]. So scientists proposed that music allowed a more holistic encoding to facilitate recognition only in AD patients, and music heightened arousal through better attention in AD patients [18].

Though there are increasing articles on the cognitive effect of music therapy for AD, the mechanisms of music therapy are less discussed. Neuroplasticity mechanism, neurogenesis, regeneration and repair mechanism, neuroendocrine mechanism and neuropsychiatric mechanism are the four main theories.

Although there are some researches which demonstrate that MT is beneficial for preserving cognition of dementia especially of AD, these are not convincing enough. So the evidence of its effectiveness is still insufficient. And we need much more clinical trials with cohort, randomized, blinded, uniform (such as uniformities of frequency, time of intervention, and different kinds of control), and rigorous methodological investigations of the MT not only just for the immediate effect, but also for the long-time effect [44]. Another important thing which we must note is that MT is just a complementary therapy in the strategy for AD. Most researchers did not stop anti-dementia drug interventions especially Acetylcholinesterase inhibitors during MT [10, 11, 15, 23, 24]. And neuroscientists always did not change the doses of anti-dementia medications with MT during the clinical trials. Besides, many evidences are coming from dementia patients at the mild and moderate stage [11, 19, 22, 23, 26, 27]. So we should not stop drug interventions during MT and MT must be started up as early as possible. It is likely that the effect of MT for protecting cognition is not significant when patients are at the severe stage.

In addition to above, combining MT with other adjuvant interventions such as dance, art, video game, physical exercise, and so on, is another area for research and clinical use [28]. The unified method may improve motor and cognitive impairment, in company with reducing psychiatric symptoms of AD patients. And the synergistic action between MT and the therapists for the improvement effect of AD is raised. A document pointed out that decreased problematic behaviors of AD were found with MT and verbal contact from the therapist [41]. So a professional and excellent therapist also plays an important role during the course of MT.

MT can be considered a non-pharmacological intervention which has the potential effects to reduce cognitive decline, improve neuropsychiatric symptoms, and enhance the QOL of AD [34]. Researches have demonstrated that MT can protect cognition of AD especially autobiographical and episodic memories, psychomotor speed, executive function, and global cognition. However, it is just an adjunct method for interventions of AD. So patients should not discontinue medications during MT and it must be started at the early stage of dementia even before dementia. Besides, more clinical trials with prospective, randomized, blinded, uniform and rigorous methodological investigations are needed to add more evidences to support the effect of MT for AD. And combination method with dance, art, video game, physical exercise, and so on is excitingly helpful. We should make a therapeutic strategy individually according to preference and physical endurance of every patient.