The effects of auditory stimulation on heart rate variability in healthy individuals with normal hearing and with hearing loss: a systematic review and meta-analysis.

All nine studies were cross-sectional: they measured heart rate variability in silence and then while sound played, which can show an association but cannot show that the sound caused the change. Despite the title, nobody in any included study had hearing loss, and children were also excluded. The review therefore says nothing about the people it appears to be about, and nothing at all about hearing loss. The one positive primary result came from pooling six studies that had each found nothing on its own, and the difference is small and sits close to the no-effect line, so it may not hold up. The individual studies were tiny, between 11 and 40 people each, and the sounds, volumes and lengths varied so much between them that they are hard to compare. Only one study used white noise, so its results could not be compared with the others. Publication bias could not be checked because there were fewer than 10 studies for each outcome. Eight of the nine studies came from Brazil and participants were mostly young adults, averaging 22.5 years, so the findings may not apply to older people or to other populations.

The only funding statement given is that the study was financed in part by CAPES, a Brazilian government funding agency, Finance Code 001.

Do not read the significant RMSSD result as proof that sound changes heart rhythm, or as a step towards using heart rate variability to screen hearing. It came from pooling six studies that each found nothing alone, the difference is small and close to the no-effect line, and the authors rate the certainty of this evidence as low and say more evidence is needed before HRV could be considered for hearing screening.