First investigation of hearing in humans when they are close to death

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Hearing is widely thought to be the last sense to go in the dying process.

Now UBC researchers have evidence that some people may still be able to hear while in an unresponsive state at the end of their life.

This research, published recently in Scientific Reports, is the first to investigate hearing in humans when they are close to death.

Using electroencephalography (EEG), which measures electrical activity in the brain, the researchers analyzed data collected from healthy control participants, from hospice patients when they were conscious, and from the same hospice patients when they became unresponsive.

The patients were receiving palliative care at St. John Hospice in Vancouver.

“In the last hours before an expected natural death, many people enter a period of unresponsiveness,” says study lead author Elizabeth Blundon, who was a Ph.D. student in the department of psychology at the time of the study.

“Our data shows that a dying brain can respond to sound, even in an unconscious state, up to the last hours of life.”

This new insight into the dying brain’s response to sound can help family and friends bring comfort to a person in their final moments.

The researchers introduced study participants to various patterns of common and rare sounds that changed frequency. When the rare tone pattern occurred, both groups responded by giving a pre-arranged signal.

The researchers monitored the brain’s response to those tones using EEG and found that some dying patients responded similarly to the young, healthy controls – even when they were hours away from death.

“We were able to identify specific cognitive processes from the neuro-typical participants as well as the hospice patients,” says Lawrence Ward, a professor in the department of psychology at UBC.

“We had to look very carefully at the individual control participants’ data, to see if each one of them showed a particular type of brain response before we felt confident that the unresponsive patient’s brain reacted similarly.”

This study was adapted from a European study that explored brain responses to sound in individual healthy participants, and in minimally conscious and unresponsive brain-injured patients. The UBC researchers applied a similar paradigm to actively dying unresponsive patients.

Blundon and Ward collaborated with Dr. Romayne Gallagher, a palliative care physician at St. John Hospice who has since retired. The research required patients to give their consent in advance. Thirteen families participated and brain recordings were obtained from five patients when they were unresponsive.

In Gallagher’s 30 years of treating dying patients, she has witnessed positive reactions in people when loved ones spoke to them in their final moments. Gallagher and her colleagues often wondered if hearing was the last sense to go. She contacted Ward to see if this theory could be proven.

“This research gives credence to the fact that hospice nurses and physicians noticed that the sounds of loved ones helped comfort people when they were dying,” says Gallagher.

“And to me, it adds significant meaning to the last days and hours of life and shows that being present, in person or by phone, is meaningful. It is a comfort to be able to say goodbye and express love.”

Blundon says what while the evidence of brain activity supports the idea that a dying person might be hearing, they can’t confirm whether people are aware of what they’re hearing.

“Their brains responded to the auditory stimuli, but we can’t possibly know if they’re remembering, identifying voices, or understanding language,” says Blundon.

“There are all these other questions that have yet to be answered. This first glimpse supports the idea that we have to keep talking to people when they are dying because something is happening in their brain.”


Death is a part of natural life; however, society is notorious for being uncomfortable with death and dying as a topic on the whole. Many caregivers experience a level of burden from their duties during end-of-life care.

This burden is multi-faceted and may include performing medical tasks, communicating with providers, decision-making and possibly anticipating the grief of impending loss. Similarly, many healthcare providers across the spectrum of care feel unprepared to provide end-of-life care or communicate with patients and families about the complex topics related to death and dying.

They can attribute this to the fact that during formal education these topics were not discussed or only briefly talked about.[1] 

It is imperative that patients and families have access to the care and support they require when entering a terminal phase of life. This phase is different for each patient, and the needs may differ for each patient and family, but it is vital for healthcare providers to provide care and support in a way that respects the patient’s dignity and autonomous wishes.

Pathophysiology

The vast majority of patients who experience a natural death, meaning no medical, life-saving interventions to counter the process, follow a stereotypical pattern of signs and symptoms in the time leading up to death. 

This time frame is often referred to as “actively dying” or “imminent death.” It is important for healthcare providers to be familiar with this process, not only so they know what to expect when providing direct care to patients during this time, but also so they can guide the family in understanding what to expect during this process and providing support as needed.

  • Early stage: Loss of mobility and becoming bed bound; loss of interest or ability to drink and eat; cognitive changes to include increased time sleeping or experiencing delirium. Delirium can be a hyperactive or agitated state or a hypoactive state. The trademark point of delirium is there is an acute change in the level of arousal.[2]
  • Middle stage: Further decline in mental status to becoming obtunded or slow arousal with stimulation and only brief periods of wakefulness. Patients often exhibit the “death rattle” which a noisy breathing pattern caused by a pooling of oral secretions due to the loss of the swallowing reflex.
  • Late stage: Coma; fever, possibly due to aspiration pneumonia; an altered respiratory pattern which can be periods of apnea alternated with hyperpnea or irregular breathing; and mottled extremities due to the constriction of the peripheral circulation 

The timeline for each patient is variable. A patient may experience these signs and symptoms over 24 hours or for longer than 14 days.[3]

References

1.Kerr AM, Biechler M, Kachmar U, Palocko B, Shaub T. Confessions of a Reluctant Caregiver Palliative Educational Program: Using Readers’ Theater to Teach End-of-Life Communication in Undergraduate Medical Education. Health Commun. 2020 Feb;35(2):192-200. [PubMed]

2.Hui D, Frisbee-Hume S, Wilson A, Dibaj SS, Nguyen T, De La Cruz M, Walker P, Zhukovsky DS, Delgado-Guay M, Vidal M, Epner D, Reddy A, Tanco K, Williams J, Hall S, Liu D, Hess K, Amin S, Breitbart W, Bruera E. Effect of Lorazepam With Haloperidol vs Haloperidol Alone on Agitated Delirium in Patients With Advanced Cancer Receiving Palliative Care: A Randomized Clinical Trial. JAMA. 2017 Sep 19;318(11):1047-1056. [PMC free article] [PubMed]

3.Durepos P, Sussman T, Ploeg J, Akhtar-Danesh N, Punia H, Kaasalainen S. What Does Death Preparedness Mean for Family Caregivers of Persons With Dementia? Am J Hosp Palliat Care. 2019 May;36(5):436-446. [PubMed]


More information: Elizabeth G. Blundon et al, Electrophysiological evidence of preserved hearing at the end of life, Scientific Reports (2020). DOI: 10.1038/s41598-020-67234-9

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