Hospital noises disturb sleep

By Sarah Guy

Common hospital noises such as human conversations, paging systems, intravenous (iv) alarms sounding, and doors closing easily disturb patients' sleep, according to US study results.

Electronic noises aroused the study participants more than human or external (eg, traffic) noises did, and when presented during rapid eye movement (REM) sleep, hospital sounds caused a sustained elevation of instantaneous heart rate, say the researchers.

"Preservation of patients' sleep should be a priority for contributing to improved clinical outcomes for patients who are hospitalized," write Orfeu Buxton (Harvard Medical School, Boston, Massachusetts) and co-authors in the Annals of Internal Medicine.

The arousal probability profiles that emerge from their study have the potential to influence design, construction, engineering, building materials, monitoring and communication equipment, and care-giving protocols in hospitals, to preserve sleep and enhance environments in healing, they say.

The team exposed a group of 12 healthy volunteers aged a mean 27 years to hospital-recorded acoustic stimuli for up to 10 seconds during 2 nights' sleep. Noise exposure began at 40 dBA (decibels) and increased in 5 dBA increments until the participant was aroused, their sleep stage changed, or the 70 dBA maximum was reached.

Louder noises caused more sleep disruption, report the researchers, and electronic noise (iv alarms) had a higher adjusted arousal probability than human voices. Approximately 99% of patients woke up to iv alarm noises at 50 dBA during N2 sleep ‑ the most abundant stage ‑ compared with approximately 84% who woke up on hearing conversation at the same decibel.

Non-REM sleep, including sleep stages N2 and N3, occurs as a person moves from drowsiness into deep sleep, explains the research team.

The greatest change in heart rate (measured using electrocardiograms, electroencephalograms, electrooculograms, and electromyograms) was recorded among participants during REM sleep, observe Buxton et al.

Specifically, participants' median heart rates increased by approximately 10.0 beats per minute between the 10 seconds preceding the onset of sound and the end of the sound recording, compared with an increase of approximately 0.4 beats per minute during N2- and N3-stage sleep.

Study limitations mean that the results may underestimate the actual effect of hospital noise on sleep, remark the researchers. Participants were young and healthy, while the typical hospital patient would be older and could have medical and psychiatric conditions as well as be using medication ‑ all factors known to hinder (particularly N3 stage) sleep.

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