Abstract and Introduction
Age is a risk factor for dementia, and also for most cancers. Surprisingly, rates of cancer appear to be lower in individuals with dementia and vice versa. Genetic mechanisms could underpin this inverse relationship and are outlined, but underdiagnosis must also be taken into account. Individuals with cancer and dementia pose unique challenges to healthcare professionals owing to the potential for impaired decision-making capacity, poor communication and difficulties following medication regimes. Mild cognitive impairment and 'chemo brain' should be differentiated from progressive neurodegeneration.
Dementia is a progressive neurodegenerative condition that increases with age. An aging population has led to a rapid increase in the prevalence of dementia. Age is a risk factor for most cancers and estimates suggest that by 2030, 70% of all cancers will occur in elderly people.
The increasing prevalence of these conditions has serious implications on healthcare provision and the healthcare economy. Economic data on the cost of dementia are available from the UK, USA, western Europe and developed countries, and less from developing ones – we refer to economic data from the UK in this review. According to the Global Burden of Disease estimates for the 2003 World Health Report, dementia contributed 11.2% of years lived with disability in people aged 60 years and older, along with stroke (9.5%), musculoskeletal disorders (8.9%), cardiovascular disease (5.0%) and all forms of cancer (2.4%).
Given that both cancer and dementia are seen as diseases of elderly people, the expectation is that there will be a significant overlap of the two conditions. However, there appears to be a disconnect between the prevalence rates of the two conditions occurring together. A small, but growing, body of evidence appears to show lower rates of cancer in patients diagnosed with dementia, especially Alzheimer's dementia, as compared with cognitively intact matched controls;[4–6] and a lower incidence of Alzheimer's dementia in cancer survivors. Genetic links between neurodegeneration and cell proliferation have been suggested, but population-based studies also suggest that underdiagnosis might be responsible for some of the mismatch.
The diagnosis and treatment of cancer is associated with high levels of psychological distress in patients and their families.[8,9] Many survivors display important symptoms of psychological distress that are related to the continuing effects of cancer and its treatment. A diagnosis of cognitive impairment or dementia is a well-established component of frailty scores, which are helpful in determining prognosis and making treatment choices. However, individuals with dementia who are diagnosed with cancer pose unique challenges in clinical practice owing to impairments in understanding, communication, capacity to consent and issues related to death and dying. Patients' relatives and carers are called on to make surrogate decisions for them when they lack the capacity to do so, and this can be distressing for both groups.
In the first part of this review, we look at current evidence in the area of overlap between cancer and dementia. In the 'hands on' second section, the authors address common clinical considerations, such as the differential diagnosis of dementia, assessment of decision-making capacity and the management of pain and distress.
Aging Health. 2013;9(3):307-319. © 2013 Future Medicine Ltd.