Intellectual disability, in relation to someone over the age of 5 years, is defined as having 'significant sub-average general intellectual functioning; and significant deficits in adaptive behaviour, each of which became manifest before the age of 18 years'. 
Persons who have an intellectual disability learn more slowly and may not easily comprehend issues around death and dying. The intellectually disabled person may be the patient or a family member of someone who is dying, so support could be needed during the illness or into bereavement.
People with an Intellectual Disability are likely to have difficulty understanding the more abstract concepts or euphemisms associated with death, such as 'to pass away'. It is important to carefully explain the situation as they may have problems with expressive and receptive communication.
The life expectancy of those with an intellectual disability has increased over the years, so the numbers and proportion that are living into old age are increasing.  However, they have higher age-specific mortality rates from a range of health problems that are undiagnosed due to lack of access to primary and secondary prevention as well as medical services.  This means for example, that more people with an Intellectual disability will die from cancer. However, behavioural and developmental issues can be challenging and sometimes make management of these clients difficult. This could be from diagnosing problems or controlling symptoms and may require interpretation of nonverbal or alternative communication strategies. 
Some persons will live independently, whereas others will be in group homes or larger congregated care facilities. The staff in these facilities are ideally placed to help with communication and to interpret behaviour when symptoms develop. They may be the only people who know the person well, particularly for the generation of people who are now ageing, and were separated from their families due to early institutionalisation. Issues of collusion around prognosis and in breaking bad news can be present in the families of those who have intellectual disabilities however this is not always the case with Intellectual Disability health professionals. 
Many care staff in group homes are trained in disability support and seldom have a nursing background. This also raises issues around their education and support, and for the other residents, in relation to death and dying. Many intellectual disability services will not necessarily think of referral to specialist palliative care.
In Australia, many persons with intellectual disability continue to live with their ageing parents. It is not unusual for parents to continue caring for their adult children until they become too frail to care for their child or they die. People with intellectual disability are unlikely to have a spouse or adult children, thus in later life their closest family members are likely to be a sibling or more distant relative. The law regarding substitute decision making will vary with each jurisdiction, and practitioners should be aware of the relevant provisions for guardianship in their state.