States worse than death
A paper published last year in a journal of the American Medical Association reported findings of a study that asked patients in hospital with serious illnesses whether they considered certain states of debility as worse than death.
A significant percentage of patients rated each evaluated state of serious functional debility as equal to or worse than death. A majority of respondents considered the following health states as the same or worse than death: bowel and bladder incontinence, requiring a breathing tube to live, relying on a feeding tube to live, and needing care from others all the time.
The authors of the paper conclude that hospitalized patients with serious and potentially life-limiting illnesses are at high risk for experiencing outcomes that many would consider to be worse than death. Nonetheless, such preferences are commonly ignored, assuming implicitly or explicitly that death is an outcome to be avoided no matter what the alternatives are.
This study involved patients in just one US hospital, so the findings may not apply in all hospitals in the UK. Nevertheless, it makes sense to prepare an Advance Decision to refuse treatment if you have a clear view as to what states of debility you would wish to avoid, even if death is brought forward.