Background Multiple tools exist to aid prognosis at end of life, yet predicting the length of time to death once the person is unresponsive and deemed to be ‘imminently dying’ remains fraught with uncertainty. Knowing approximately how many hours or days their dying loved one has left is crucial for both families and clinicians to guide decision making and planning end-of-life care. Previous research has produced useful indicators, but definitive data on length of time from unresponsiveness to death are not reported in the literature. This research sought to determine the length of time between becoming unresponsive and death.

Method A retrospective clinical audit of electronic records of 786 patients receiving specialist palliative care as inpatients, at home, and in aged care homes was conducted across a 10-month period. We analysed the time from the first Karnofsky 10 score to death and used Kaplan-Meier survival analysis to determine the duration of patient’s final phase of life, taking into account variation across age, sex, diagnosis, and location of death.

Results From the first time the patient was scored as Karnofsky 10, 49% of patients were unresponsive for longer than one day, with a median duration of 2 days. Regardless of age, the probability of not surviving is identical across all age groups on day two. Having adjusted for age, malignancy, gender, and location, the likelihood of death within 4 days is over 75%. The data also reveals that, regardless of diagnosis, there is a tipping point at around 20–30 days prior to death, from where there is a notable decline.

Conclusion This new data will have a major impact on clinician’s confidence when responding to the ‘how long’ question and can be used to inform decision-making at end-of-life. Findings demonstrate that the Karnofsky 10 score is a highly reliable prognostic indicator.