Noise as a sleep aid: A systematic review.

White noise is purported to mask disruptive noises in the bedroom environment and be a non-pharmacological approach for promoting sleep and improving sleep quality. We conducted a systematic review of all studies examining the relationships between continuous white noise or similar broadband noise and sleep (PROSPERO 2020: CRD42020148736). Animal studies and studies using intermittent white noise to disrupt sleep or enhance slow wave activity were excluded. Two reviewers independently screened titles and abstracts of articles from three databases and assessed risk of bias for the 38 included articles. The primary outcomes described sleep onset latency, sleep fragmentation, sleep quality, and sleep and wake duration. There was heterogeneity in noise characteristics, sleep measurement methodology, adherence to the intervention, control group conditions or interventions, and presence of simultaneous experimental interventions. There was perhaps resultantly variability in research findings, with the extremes being that continuous noise improves or disrupts sleep. Following the GRADE criteria, the quality of evidence for continuous noise improving sleep was very low, which contradicts its widespread use. Additional research with objective sleep measures and detailed descriptions of noise exposure is needed before promoting continuous noise as a sleep aid, especially since it may also negatively affect sleep and hearing.