Some groups of people with cancer are at increased risk of impairment in cognition, the higher mental functions of the brain. Although individual perceptions of cognitive function are important to quality of life in their own right and can also correlate with objective measures, their relationship to objective measures of cognitive performance is inconsistent. This paper reviews relationships between objective and subjective cognitive performance and cancer and proposes a model. Risk factors for cognitive impairment associated with cancer that are incorporated in this model include infancy, older age, previous or coexisting neurological impairment, comorbid illness associated with cognitive impairment, advanced malignancy, chemotherapy, cranial radiotherapy, interleukins, surgery, hormonal manipulations, analgesics, anticholinergics, and emotional distress. Increased awareness of cognitive issues will help health practitioners to anticipate, identify and remedy cognitive problems associated with cancer and its treatments, with important implications for patients' quality of life and functional status
