Only one in 10 very old people simply "slip away" when they die, a new study suggests.
Just 10% of the oldest old have no symptoms such as pain, distress, depression or confusion at the time of death, researchers found.
Experts from the University of Cambridge performed a retrospective analysis on 108 people who died at an average age of 91.
After examining their records and conducting interviews with loved ones, the team found symptoms of distress, pain, depression and delirium or confusion each affected 40%-50% of participants.
And most people had experienced combinations of two or more of these symptoms.
But the researchers found that these symptoms were not always treated effectively.
Pain was addressed in the majority of those who were suffering, but only effectively for half of the cases.
Only "a fraction" of those who suffered depression had treatment, the authors said.
Only 10% had no such symptoms.
However, most participants reported some level of comfort during their final illness, with only 7% being "very uncomfortable" during their final days.
The study, published in the journal BMC Geriatrics, found the very old are four times more likely to die comfortably if they pass away at home or in a care home compared to being in hospital.
People were also less likely to have reportedly died comfortably if they lived at home but relied on formal services.
The authors said the study suggested "fewer than 10% of the very old simply 'slip away'".
"Of the treatable symptoms reported, pain was addressed in the majority affected, though effectively for only half these, but only a fraction of those with depression were treated," they added.
"Nonetheless, despite high symptom prevalence when dying, death was described as comfortable for the majority."
The researchers called for improved end of life care training for people who work with those who are nearing the end of their lives.
They also highlighted a shortage of palliative care doctors in the NHS.
Lead author Dr Jane Fleming said: "We've published research before about preferences and attitudes towards death and dying and so many people are wishing, that the ideal would be, that they would die in their sleep peacefully, or slip away.
"But from these interviews we have done with relatives of people who have died, when they were asked about what sort of symptoms people experienced in that final stage, there was such a small minority who didn't have some sort of symptom.
"So that idea of dying pain free without any distress only seemed to apply to a small minority, about 10%."
She added: "How we care for the oldest members of society towards the end of their lives is one of the big issues for societies across the world.
"The UK is not the only country where an urgent review of the funding for older people's long-term care is needed, along with commitments to staff training and development in this often undervalued sector.
"It's heartening that the majority of very old people in our study, including those with dementia, appear to have been comfortable at the end-of-life, but we need to do more to ensure that everyone is able to die comfortably, wherever they are."
Co-author Rowan Calloway said: "In the UK, we particularly need to address the current shortage of palliative care doctors in the NHS, where training numbers are not going up to match demand, but the shortage is even greater in developing countries.
"In the future, community care will be increasingly reliant on non-specialists, so it will be crucial that all members of the multi-disciplinary teams needed to support very frail older people near the end of their lives have good training in palliative and supportive care skills."
Co-author Dr Morag Farquhar, who is now based at the University of East Anglia, said: "Improving access to supportive and palliative care in the community should be a priority, otherwise staying at home may not always be the most comfortable setting for end-of-life care, and inadequacies of care may lead to admission before death in hospital."
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