OBJECTIVE: This study examines the influence of cognitive impairment, premorbid intelligence, and decision-making capacity to complete advance directives on the treatment preferences for life-sustaining medical therapy in the elderly.METHOD: One hundred elderly individuals were recruited. Fifty were first referrals to specialist services with a DSM-IV diagnosis of dementia, and 50 were volunteers. Each person was asked about treatment preferences in three clinical vignettes.RESULTS: Elderly individuals who had cognitive impairment and were incapable of completing advance directives were significantly more likely to opt for life-sustaining interventions. There was no association between premorbid intelligence and treatment preferences.CONCLUSIONS: Cognitive impairment appears to influence treatment preferences for life-sustaining medical therapy. With increasing cognitive impairment, elderly individuals tend to opt for treatment interventions.