Background

Hypertension is the first risk factor for cardiovascular associated diseases. With the change of lifestyle and rhythm, the prevalence of hypertension in countries around the world is increasing year by year [1]. Negative emotions such as high-sodium diet, obesity, excessive drinking, and anxiety and depression are all risk factors for hypertension [2, 3]. Negative emotions such as anxiety and depression interact with hypertension. Previous epidemiological studies [4, 5] have found that about 38.5% of Chinese hypertensive patients are associated with anxiety, and 19.8% were associated with depression. Negative emotions such as anxiety and depression can affect the degree of hypertension and reduce the quality of life of patients by affecting the release of vascular endothelial factor, reducing vascular activity, and increasing vascular resistance [6,7,8]. Therefore, it is very important to focus on improving patients’ anxiety and depression while treating hypertension.

At present, there are many drugs for the treatment of hypertension in clinic. Although they can control hypertension to a certain extent, long-term use of drug use is easy to produce drug resistance, and it is easy to relapse after drug withdrawal. Nonpharmacological treatments can be effective in lowering blood pressure without other health risks. As one of the non-drug treatment methods, music therapy has been used as an adjuvant therapy in hypertension treatment. Currently, many scholars [9,10,11] have evaluated the psychological and physiological effects of music therapy on hypertensive patients, but the sample size of each study is small, and the research results remain different. Even though previous meta-analyses [12, 13] have analyzed the of the effect of music therapy on blood pressure in patients with hypertension, with more related studies published, updated meta-analyses on the role of music therapy for hypertention are needed. Therefore, this meta-analysis aimed to use the meta-analysis method to comprehensively evaluate the application effect of music therapy on hypertensive patients, in order to provide evidence-based basis for the treatment and management of hypertension.

Methods

We conducted and reported this meta-analysis according to the preferred reporting items for systematic reviews and meta-analyses (PRISMA) statement [14].

Document retrieval

Two authors searched PubMed, Embase, Web of Science, the Cochrane Library, Chinese National Knowledge Infrastructure (CNKI), China Biomedical Literature Database, Wanfang Databases for randomized controlled trials (RCTs) on the role of music therapy in hypertension. The retrieval time is from the establishment of the database to Oct 15, 2022. We used a combination of subject headings and free words to search. The language of searched and included publications were limited to English and Chinese. The search terms were as following: (“music” OR “music therapy” OR “sound therapy”) AND (“hypertension” OR “high blood pressure” OR “cardiovascular”)(Supplementary 1). In addition, we conducted a review search of relevant references in the included RCTs and important reviews to broaden the scope of the search.

Inclusion and exclusion criteria

The inclusion criteria for this meta-analysis were: (1) study type: RCT design; (2) study population was the hypertensive patients, who met the diagnostic criteria for hypertension: Systolic blood pressure ≥ 140mmHg and / or diastolic blood pressure ≥ 90mmHg[15, 16]; (3) intervention measures: in addition to receiving routine treatment, patients in the music group accepted the music intervention. The patients in the control group only received the same routine treatment as the music therapy intervention group; (4) The study reported the corresponding outcome indicators, and the data could be extracted.

The exclusion criteria for this meta-analysis were: (1) studies with unclear diagnosis of hypertension or hypertension complicated with risk factors for other diseases; (2) research population were special populations such as pregnant women and military personnel; (3) Low-quality reports(significant data errors, study design problems and incomplete data); (4) reviews, cases and those literature reports with data that could not be extracted for analysis.

Literature screening and data extraction

Literature screening and data extraction were conducted independently by two researchers in a blinded manner, and inconsistent literatures were reviewed and discussed. The following data were extracted according to the designed table: author, publication year, country, sample size, details of intervention measures and reported outcome indicators. The primary outcomes included systolic blood pressure, diastolic blood pressure. The secondary outcomes included heart rate, self-rating anxiety scale (SAS), self-rating depression scale (SDS), Hamilton anxiety scale (HAMA), Pittsburgh sleep quality index (PSQI).

Quality assessment

The quality of the included literature was evaluated according to the risk of bias tool [17] recommended by Cochrane library. The tool includes following items: sequence generation, allocation concealment, blinding of participants and personnel, blinding of outcome assessment, incomplete outcome data, selective outcome reporting, and “other” issues. Every item can be rated as “low risk of bias”, “high risk of bias” or “unclear risk of bias” accordingly.

Statistical analysis

We used Review Manager (RevMan) Version 5.3. software for meta-analysis. Measurement data were expressed as mean difference (MD) and 95% confidence interval (CI). In addition, we performed the heterogeneity test by the Q test, and combined with I2 to quantitatively judge the heterogeneity. If there was homogeneity among studies(I2 < 50%), a fixed-effects model was used to calculate the combined statistics; if there was heterogeneity(I2 ≥ 50%), random-effects model was used. Sensitivity analysis was performed by excluding articles one by one and then recombining the calculation. A funnel plot and Egger’s test were used to assess the publication bias of the pooled results. In this meta-analysis, P < 0.05 was considered to be statistically significant between groups.

Results

Study inclusion

A preliminary search obtained 202 relevant literatures. After screening according to the inclusion and exclusion criteria, a total of 20 RCTs [18,19,20,21,22,23,24,25,26,27,28,29,30,31,32,33,34,35,36,37] that met the criteria were finally included in this meta-analysis. The literature screening process is shown in Fig. 1.

Fig. 1
figure 1

PRISMA flow diagram of RCT selection

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Characteristics of included studies

Of the included 20 RCTs [18,19,20,21,22,23,24,25,26,27,28,29,30,31,32,33,34,35,36,37], a total of 2306 patients with hypertension were included, of whom 1154 patients received music therapy, 1152 received routine anti-hypertension treatment. The characteristics of the included studies are shown in Table 1.

Table 1 The characteristics of included studies
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The quality of included studies

The quality of included RCTs is presented in Figs. 2 and 3. The quality of the studies included in the RCTs was generally good taking into account the integrity of research design and data. Most of the RCTs reported the detailed random sequence generation methods, and random assignment concealment and blinding settings were less reported. Given the nature of music interventions, it was difficult to blind researchers. No bias on other items was found.

Fig. 2
figure 2

Risk of bias graph

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Fig. 3
figure 3

Risk of bias summary

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Meta-analysis

Systolic blood pressure

Seventeen studies [18,19,20, 22,23,24,25,26,27,28, 30,31,32,33,34,35, 37] reported changes in systolic blood pressure in patients before and after the intervention. The pooled results on systolic blood pressure results were heterogeneous (I2 = 91%), so a random-effects model was used to pool the results. The results of meta-analysis showed that the mean systolic blood pressure drop in the music therapy group was greater than that in the control group, and the difference was statistically significant (MD = − 9.00, 95%CI: − 11.99~- 6.00, P<0.001, Fig. 4).

Fig. 4
figure 4

Forest plot for systolic blood pressure change

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Diastolic blood pressure

Sixteen studies [19, 20, 22,23,24,25,26,27,28, 30,31,32,33,34,35, 37] reported changes in diastolic blood pressure in patients before and after the intervention. The pooled results on diastolic blood pressure results were heterogeneous (I2 = 94%), so a random-effects model was used to pool the results. The results of meta-analysis showed that the mean diastolic blood pressure drop in the music therapy group was greater than that in the control group, and the difference was statistically significant (MD = -6.53, 95%CI: -9.12~- 3.93, P<0.001, Fig. 5).

Fig. 5
figure 5

Forest plot for diastolic blood pressure change

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Heart rate

Five studies [24, 25, 29, 33, 37] reported changes in heart rate in patients before and after the intervention. The pooled results on diastolic blood pressure results were heterogeneous (I2 = 97%), so a random-effects model was used to pool the results. The results of meta-analysis showed that the mean heart rate drop in the music therapy group was greater than that in the control group, and the difference was statistically significant (MD = -3.76, 95%CI: -7.32~- 0.20, P = 0.04, Fig. 6).

Fig. 6
figure 6

Forest plot for heart rate change

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Other outcomes

As indicated in Table 2, the results of meta-analysis showed that music therapy reduced the SAS score(MD =-8.55, 95%CI: -12.04~-4.12), SDS score(MD = -9.17, 95%CI: -13.85~-5.18), HAMA score(MD = -3.37, 95%CI: − 5.38~- 1.36), PSQI score(MD =-1.61, 95%CI:-2.30~- 0.93) compared with routine therapy in patients with hypertension(all P < 0.05).

Table 2 The synthesized outcomes for the effects of music therapy
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Publication bias

We used funnel plots (Fig. 7) combined with Egger’s test to assess the asymmetry of funnel plots, and the results showed that there was no publication bias in each combined result (all P > 0.05).

Fig. 7
figure 7

Funnel plots for systolic and diastolic blood pressure changes

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Sensitivity analysis

After excluding each study in turn, the heterogeneity and results of the remaining included studies did not change significantly after pooling, indicating that the results were robust and reliable.

Discussions

Hypertension is a psychosomatic disease related to psychological and mental factors. Long-term mental stress is one of the risk factors for hypertension [38]. The risk of hypertension in people with long-term anxiety and worry is 1.18 times that of normal people [39]. To a certain extent, it is the physiological response of the patient’s nervous and anxious psychological state. A total of 20 RCTs were included in this meta-analysis study, which preliminarily has evaluated the effect of music therapy on blood pressure in hypertensive patients. The results of this meta-analysis indicate that music therapy is beneficial to reduce the systolic, diastolic blood pressure and heart rate, and it is helpful to reduce the anxiety, depression level and improve the sleep quality of patients with hypertension. Music therapy is safe and effective as an adjuvant therapy for hypertension and is worthy of clinical promotion.

The effects and mechanisms of music therapy in the treatment of hypertension may be explained in following aspects. Firstly, it has been reported that when the sound waves of music act on the brain, it increases the excitability of the nervous system and promotes the secretion of hormones such as acetylcholine, thereby slowing down the heart rate [40,41,42]. Secondly, music diverts the patient’s attention to the disease, reduces sympathetic nerve excitability, produces sedative and antihypertensive effects, and regulates endocrine to reduce renin-angiotensin II secretion to reduce blood pressure [43, 44]. Additionally, the sound wave acts on the brain, adjusts the functional state of the cortex, relieves anxiety and tension, thereby causing changes in physiological and psychological states [45, 46]. In addition, the vitality of the entire nervous system and cell excitability can be enhanced by pleasant music, thereby regulating human physiological activities, eliminating the individual’s tension, reducing their irritable emotions, and ultimately leading to a drop in blood pressure and an improvement in the blood supply function of the heart [47,48,49].

Music therapy is beneficial to reduce the anxiety, depression level of patients with hypertension. Currently, the pathogenesis of anxiety and depression in hypertensive patients has not been fully elucidated, and it is mostly believed that it is caused by the joint action of serum serotonin (5-HT), norepinephrine (NE) and other neurotransmitters, and is related to neurological and endocrine dysfunction [50]. Both 5-HT and NE are important neurotransmitters in the human body, which can participate in the regulation of various physiological and pathological functions such as body temperature, sleep, mental and emotional functions [51,52,53]. Studies [54, 55] have found that 5-HT and NE are in low levels in depressed patients. A study [56] has found that compared with before treatment, the levels of 5-HT and NE in the two groups increased after treatment, and the increase in the music therapy group was better than that in the control group. It has been reported that five-element music can improve the level of central neurotransmitter in patients, improve the anxiety and depression state of patients, and then improve the blood pressure control level of patients [57].

Several previous systematic reviews have evaluated the role of music therapy on the patients with hypertension. Yang et al. [58]. have analyzed a total of 7 reports and have concluded that music therapy can effectively reduce diastolic blood pressure in patients, but it does not have effect on and systolic blood pressure. Systolic blood pressure was highly heterogeneous, and no plausible explanation was given for its heterogeneity. Besides, it has been reported that music therapy is only effective for systolic blood pressure, but not significantly for diastolic blood pressure [10]. However, their research only included two literatures for meta-analysis, and it is difficult to support their views due to the small number of sample size, so the conclusions they draw should be treated with caution. Kühlmann et al. [9] have finally included 10 related studies from PubMed, Medline, Cochrane Central, Web of Science and Google Scholar databases, and analyzed that although both systolic and diastolic blood pressure had a downward trend after music therapy, the decline has not reach statistical significance. It has scientific significance and cannot explain the relationship between hypertension and diastolic blood pressure. Compared with published related studies, this study has certain advantages. more RCTs were included than previous studies. Besides, we have chosen stricter inclusion and exclusion criteria, excluding some studies that might affect the accuracy of the results. Furthermore, the evaluation of SAS score, SDS score, HAMA score, PSQI score, etc. of hypertensive patients have been added in this study, and the current research shows that these may be related to the disease control of hypertensive patients.

There are certain limitations in this study that are worth considering. Firstly, most of the included studies lack allocation concealment and double-blind implementation, and there may be selection bias in the time, and type choice of music, which may affect the results of the study. Secondly, some of the included studies did not provide the mean value of the changes before and after intervention, we calculated the coefficient by reporting the complete study, and the results may have a certain bias. Thirdly, some of the included RCTs did not fully report the characteristics of the study population and music type, and the results of some studies were heterogeneous, but there was insufficient data for subgroup analysis, so the results of this study should be treated with caution.

Conclusions

In conclusion, music therapy can effectively reduce blood pressure and heart rate in patients with hypertension, reduce anxiety and depression levels, and improve sleep quality of patients, thereby improving blood pressure control and prognosis of patients. Compared with drug therapy, music therapy, as a low-cost, easy-to-operate, non-invasive therapy, can reduce medical expenses while achieving therapeutic effects, and it is an adjuvant therapy that clinicians can provide independently. The music therapy is worthy of discussion and application in clinical practice for hypertension management. Still, it is recommended that future studies be designed strictly in accordance with the RCT requirements, and explore the influence of music therapy on more indicators of hypertensive patients, and evaluate the intervention time, music type, playing time, and listening style, so as to provide support for the clinical application of music therapy intervention for hypertensive patients.