• Music and vocal interventions probably reduce heart rates in preterm infants compared to standard care during the intervention. This beneficial effect was even more substantial and confident after the intervention suggesting a long-lasting relaxing and stabilising effect.
• We found no harmful effects from music and voice. However, many studies did not explicitly explore the possibility of unwanted effects.
• We found no evidence of any other clear beneficial or harmful effects of the interventions on the infants, their parents, and parent-infant bonding. More good-quality evidence is needed to draw further clear conclusions.
What is a preterm infant?
Preterm infants are newborns born before the gestational age of 37 weeks and often have to be treated for weeks to months in the stressful environment of a neonatal intensive care unit to survive.
Why examine the potential benefits of music and vocal interventions for preterm infants and their parents?
Preterm infants are at risk for various health issues. Preterm birth is a traumatic event for the parents as well. Therefore, complementary approaches such as music and vocal interventions are increasingly used in neonatal care to improve physical and mental health in preterm infants and their parents. However, various studies and reviews show ambiguous results in the efficacy of a variety of music and vocal interventions. A more comprehensive and rigorous systematic review is needed to address conflicting data and reviews.
What did we want to find out?
We wanted to find out if music and vocal interventions benefit:
• the health and development of the preterm infant
• the mental health of the parents and their bonding with the infant
We wanted to know which types, delivery, duration, and frequency of music and vocal interventions would best support infants and parents. We aimed to find out if the intervention can cause any harmful effects.
What did we do?
We searched for studies that compared:
• music and vocal interventions for preterm infants (and parents) compared to usual standard care in the neonatal unit that did not include any music or vocal interventions.
We compared and summarised their results and rated our confidence in the evidence, based on factors such as study methods and sizes.
What did we find?
We found 25 studies that involved 1532 preterm infants and 691 parents. The biggest study was in 272, and the smallest was in 17 preterm infants. Within the studies from around the world, mainly the immediate effect of music and voice was examined in the moments of intervention and minutes post-intervention, whereas two studies wanted to know if there would be a beneficial effect on long-term development at two years. Most studies were funded by University/Health Department/Hospital research funds and local medical/health foundations. The reported music and vocal interventions varied widely in type, delivery, frequency, and duration. They were mainly characterised by calm, soft, musical parameters in lullaby style, often integrating the mother's voice live or recorded, defined as music therapy when provided by a music therapist within a therapeutic relationship or music medicine when delivered as "medicine" by medical and healthcare professionals.
In preterm infants (and their parents), compared to standard care without any music and vocal interventions:
• Music and voice make no difference to the oxygen saturation during the intervention (10 studies with 958 infants) and may make no difference after the intervention (7 studies with 800 infants).
• Music and voice may make no difference in the respiratory rate during the intervention (7 studies with 750 infants) and after the intervention (5 studies with 636 infants).
• Music and voice may lead to a beneficial reduction in infants' heart rates (11 studies with 1014 infants). This beneficial effect was even more substantial and confident after the intervention, leading to a medium-to-large beneficial reduction in the heart rate (5 studies with 636 infants).
• We are uncertain if the intervention may influence infant long-term development at two years of age (2 studies with 69 infants).
• We are uncertain about the possible effect of music therapy on parental state-trait anxiety (4 studies with 97 participants) and postnatal depression (2 studies with 67 infants).
• We are very uncertain about a possible effect on parental state anxiety (3 studies with 87 parents).
• We found no studies which reported harmful effects of music or voice.
What are the limitations of the evidence?
We are confident that music and voice do not reduce oxygen saturation during the intervention compared to standard care. We are confident in our results of the substantial beneficial effect on the heart rate in preterm infants after the intervention. There are not enough rigorous studies (many small studies with poor recording standards) to be certain about the results of all other outcomes that we assessed in the infants and their parents. There is further uncertainty about music delivery and for which duration and frequency music works best.
How up-to-date is this evidence?
The evidence is up-to-date to 12 November 2021.
Music/vocal interventions do not increase oxygen saturation during and probably not after the intervention compared to standard care. The evidence suggests that music and voice do not increase infant development (BSID) or reduce parental state-trait anxiety. The intervention probably does not reduce respiratory rate in preterm infants. However, music/vocal interventions probably reduce heart rates in preterm infants during the intervention, and this beneficial effect is even stronger after the intervention, demonstrating that music/vocal interventions reduce heart rates in preterm infants post-intervention. We found no reports of adverse effects from music and voice. Due to low-certainty evidence for all other outcomes, we could not draw any further conclusions regarding overall efficacy nor the possible impact of different intervention types, frequencies, or durations. Further research with more power, fewer risks of bias, and more sensitive and clinically relevant outcomes are needed.
Preterm birth interferes with brain maturation, and subsequent clinical events and interventions may have additional deleterious effects. Music as therapy is offered increasingly in neonatal intensive care units aiming to improve health outcomes and quality of life for both preterm infants and the well-being of their parents. Systematic reviews of mixed methodological quality have demonstrated ambiguous results for the efficacy of various types of auditory stimulation of preterm infants. A more comprehensive and rigorous systematic review is needed to address controversies arising from apparently conflicting studies and reviews.
We assessed the overall efficacy of music and vocal interventions for physiological and neurodevelopmental outcomes in preterm infants (< 37 weeks' gestation) compared to standard care. In addition, we aimed to determine specific effects of various interventions for physiological, anthropometric, social-emotional, neurodevelopmental short- and long-term outcomes in the infants, parental well-being, and bonding.
We searched Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, Embase, CINAHL, PsycINFO, Web of Science, RILM Abstracts, and ERIC in November 2021; and Proquest Dissertations in February 2019. We searched the reference lists of related systematic reviews, and of studies selected for inclusion and clinical trial registries.
We included parallel, and cluster-randomised controlled trials with preterm infants < 37 weeks` gestation during hospitalisation, and parents when they were involved in the intervention. Interventions were any music or vocal stimulation provided live or via a recording by a music therapist, a parent, or a healthcare professional compared to standard care. The intervention duration was greater than five minutes and needed to occur more than three times.
Three review authors independently extracted data. We analysed the treatment effects of the individual trials using RevMan Web using a fixed-effects model to combine the data. Where possible, we presented results in meta-analyses using mean differences with 95% CI. We performed heterogeneity tests. When the I2 statistic was higher than 50%, we assessed the source of the heterogeneity by sensitivity and subgroup analyses. We used GRADE to assess the certainty of the evidence.
We included 25 trials recruiting 1532 infants and 691 parents (21 parallel-group RCTs, four cross-over RCTs). The infants gestational age at birth varied from 23 to 36 weeks, taking place in NICUs (level 1 to 3) around the world. Within the trials, the intervention varied widely in type, delivery, frequency, and duration. Music and voice were mainly characterised by calm, soft, musical parameters in lullaby style, often integrating the sung mother's voice live or recorded, defined as music therapy or music medicine. The general risk of bias in the included studies varied from low to high risk of bias.
Music and vocal interventions compared to standard care
Music/vocal interventions do not increase oxygen saturation in the infants during the intervention (mean difference (MD) 0.13, 95% CI -0.33 to 0.59; P = 0.59; 958 infants, 10 studies; high-certainty evidence). Music and voice probably do not increase oxygen saturation post-intervention either (MD 0.63, 95% CI -0.01 to 1.26; P = 0.05; 800 infants, 7 studies; moderate-certainty evidence). The intervention may not increase infant development (Bayley Scales of Infant and Toddler Development (BSID)) with the cognitive composition score (MD 0.35, 95% CI -4.85 to 5.55; P = 0.90; 69 infants, 2 studies; low-certainty evidence); the motor composition score (MD -0.17, 95% CI -5.45 to 5.11; P = 0.95; 69 infants, 2 studies; low-certainty evidence); and the language composition score (MD 0.38, 95% CI -5.45 to 6.21; P = 0.90; 69 infants, 2 studies; low-certainty evidence). Music therapy may not reduce parental state-trait anxiety (MD -1.12, 95% CI -3.20 to 0.96; P = 0.29; 97 parents, 4 studies; low-certainty evidence).
The intervention probably does not reduce respiratory rate during the intervention (MD 0.42, 95% CI -1.05 to 1.90; P = 0.57; 750 infants; 7 studies; moderate-certainty evidence) and post-intervention (MD 0.51, 95% CI -1.57 to 2.58; P = 0.63; 636 infants, 5 studies; moderate-certainty evidence). However, music/vocal interventions probably reduce heart rates in preterm infants during the intervention (MD -1.38, 95% CI -2.63 to -0.12; P = 0.03; 1014 infants; 11 studies; moderate-certainty evidence). This beneficial effect was even stronger after the intervention. Music/vocal interventions reduce heart rate post-intervention (MD -3.80, 95% CI -5.05 to -2.55; P < 0.00001; 903 infants, 9 studies; high-certainty evidence) with wide CIs ranging from medium to large beneficial effects. Music therapy may not reduce postnatal depression (MD 0.50, 95% CI -1.80 to 2.81; P = 0.67; 67 participants; 2 studies; low-certainty evidence). The evidence is very uncertain about the effect of music therapy on parental state anxiety (MD -0.15, 95% CI -2.72 to 2.41; P = 0.91; 87 parents, 3 studies; very low-certainty evidence). We are uncertain about any further effects regarding all other secondary short- and long-term outcomes on the infants, parental well-being, and bonding/attachment. Two studies evaluated adverse effects as an explicit outcome of interest and reported no adverse effects from music and voice.