Five-year follow-up of a community-based, 77+ old cohort including incident dementia cases was used to evaluate the impact of dementia on the risk of death, taking into account other chronic conditions potentially related to death, and contrasting Alzheimer's disease (AD), and vascular dementia (VaD). In this population, 70% of the dementia cases died during the five years after diagnosis, with a mortality rate specific for dementia of 2.4 per 100 person-years. After controlling for sociodemographic variables and comorbidity, 14% of all deaths could be attributed to dementia with a risk of death among demented subjects twice as high as that for non-demented people. Mortality risk ratios were 2.0 (95% confidence interval 1.5-2.7) for AD and 3.3 (95% confidence interval 2.0-5.3) for VaD. This study confirms that dementing disorders are a major risk factor for death. Even in the oldest old (85+), dementia shortens life, especially among women.