What is Known
Severity of dementia is predictive of life expectancy independent of comorbidities, although significant individual variation is seen. It is not clear whether the type of dementia is of prognostic significance. In a large US study  the twelve variables that best predicted survival were:
- Length of stay
- Male gender
- Pressure ulcers
- Total functional dependence
- Insufficient intake
- Bowel incontinence
- Body mass index
- Weight loss
- Congestive heart failure.
Medical complications including aspiration episodes, hallucinations / extra-pyramidal symptoms, and duration of dementia have been shown in other studies to indicate a worse prognosis. [2,3] Care provided may also impact on prognosis - a palliative approach may improve outcomes because less adverse effects from treatments are experienced.  Whilst the evidence regarding prognostic factors is inconsistent, no well-validated risk scores exist. 
When family caregivers have a general understanding of the prognosis and trajectory of dementia, less inappropriate treatments are likely to be given, and the focus of care is more likely to be on comfort. 
The issue of withdrawal of long-term medications for comorbid conditions as part of a palliative approach to caring for patients with dementia has been reviewed. More evidence to guide this practice is needed, including consideration of benefit and burden of comorbid medications and modification of treatment targets according to the patient’s level of function. 
Assessments of benefit and burden of common, invasive treatments in people with dementia have been studied:
- Studies that examine the outcomes of enteral tube feeding in patients with dementia do not suggest benefit in terms of survival, nutritional status or prevention of pressure sores, although more research on this topic is needed and the evidence to support clinical practice is limited. [6,7] Risks of enteral feeding are substantial.  Evidence based approaches for discussing feeding issues with family caregivers when fevers due to aspiration are occurring have been identified. 
- Outcomes of cardiopulmonary resuscitation and mechanical ventilation in this population are very poor and decrease with older age. Survival rates at 30 days are under 10% for those over 79. 
Advance care planning
Since dementia impairs decision making as it progresses the need for advance care planning is well recognised, in order to allow the person to influence their future care decisions at a time while they still have capacity.  Advance care planning can use a number of different strategies to allow the person to direct their future care. These include:
- Creation of a formal written advance directive
- Appointing proxy decision makers and / or
- Supporting and documenting a process of discussion between the person, their clinicians and their proxy decision makers.
The extent to which the presence of an advance directive influences decision making has not been well studied. There is limited evidence that advance care planning influences the type of care that patients actually receive.  Studies often measure documents completed rather than patient or family-centered outcomes, which would explore the impact and effects of advance care planning on end-of-life experiences. 
The acceptability of advance care planning in this population, and the point at which people wish to make an advance care plan, has not been well studied. [11,13] Studies undertaken in the high level residential aged care setting reveal that many residents are no longer competent to participate in advance care planning, so timing of the advance care planning discussions is therefore crucial if the person is to have any involvement themselves.  It is known that the reliability and stability of patients’ decisions decreases with the progression of dementia.  It is suggested that a cut-off point for capacity may occur at a Mini-Mental State Examination score of around 18-20, after which caregivers have increasing responsibility for decision making. Mini-Mental State Examination score alone is not an assessment of competence. 
It seems that progression of cognitive impairment may be associated with increased preference for active treatment, whilst being Caucasian and having higher educational background are associated with more likelihood of having an advance directive, which is usually used as a tool to limit treatments other than pain control and comfort measures. 
Possible strategies to engage residents in structured and cognitively appropriate end-of-life care discussions have been been identified. Decision making processes for caregivers are complex and painful, and support is needed to assist them.  Factors that may be important in the process are the context of care (geographic location, caregiver education, ethnicity, religious beliefs, caregiver understanding of the disease process, and so on) and involvement of clinicians in decision making. Failure of professionals to discuss prognosis may be a barrier to timely advance care planning, whereas active involvement of professionals in initiating the process may improve its effectiveness. 
Caregivers’ perceptions of the person’s quality of life may also influence decisions about treatments that have a goal of prolonging life. [5,11] The burden of decision making is not easy for caregivers and the choice to withhold or withdraw treatment is more difficult than the choice to consent to active treatment. Education and support for caregivers, both family and professional, are therefore required. [13,10]
Implications for practice
- Dementia is a terminal illness, and although prognosis is not able to be reliably predicted for a given individual, the progression of the illness has a predictable trajectory. Caregivers and families should be assisted to understand this trajectory, to help them make appropriate care decisions.
- Treatment decisions should be made based on consideration of the benefit and burden of any proposed treatment. Treatment decisions should be regularly reviewed as the illness changes or sentinel events occur (eg, recent hospital admission, occurrence of aspiration pneumonia, decline in function). This includes decisions about continuing treatment of comorbidities, as well as whether or not, and when, to initiate any new treatments for comorbid or acute illnesses, or to transfer a person with dementia to an acute care setting. In particular, transfers for acute hospital care, and artificial feeding, are known to have a negative overall effect on quality of life for people with severe dementia, and to provide little benefit.
- Dementia inevitably affects decision making capacity. Advance care planning is therefore very important, and the timing of the advance care planning process is significant if the person themselves is to be able to contribute meaningfully to decision making. The time of nursing home admission is generally too late for this to occur.
- Family caregivers may find advance care planning for a person with dementia extremely difficult. They require support and sensitive education, as well as active encouragement by their health care providers: this can help initiate an advance care planning process in a timely way.