Mortality after a Diagnosis of Dementia in a Population Aged 75 and Over in Spain

OBJECTIVES: To examine the impact of incident dementia on the risk of death, taking into account other chronic illnesses potentially related to death. DESIGN: Six-year, prospective, two-phase, observational cohort study. SETTING: 8 municipalities from a rural area in Girona (Spain). PARTICIPANTS: A representative community-based cohort of 1,153 adults aged over 70 living at home at study enrolment. MEASUREMENTS: Surviving participants underwent detailed clinical evaluation and were assessed by means of the Cambridge Examination for Mental Disorders of the Elderly. Relatives of deceased participants were interviewed using the Retrospective Collateral Dementia Interview. Mortality rates and relative risk of death for subjects with a diagnosis of dementia were calculated. The Cox proportional hazards regression model was used to assess the relationship between mortality and the diagnosis of dementia. RESULTS: In this cohort, 40.0% (n = 49) of the subjects with a diagnosis of dementia died. The mortality rate specific to dementia was 1.0 per 100 person-years. Mortality risk ratios for dementia were 1.79 in men [95% confidence interval (CI) = 1.06-3.02], and 3.14 in women (95% CI = 2.04-4.85). The population death risk attributable to the diagnosis of dementia in our cohort was 11.8%. The most important mortality risks were severe dementia (hazard ratio = 5.7, 95% CI = 3.7-8.6), cancer (hazard ratio = 3.2, 95% CI = 2.2-4.5), heart disease, and an age over 85 (hazard ratio = 1.4, 95% CI = 1.1-1.9). CONCLUSION: Dementia is a major risk factor for death in advanced age, with the highest mortality rates in women. Moderate and severe dementia was associated with an increased mortality risk even after appropriate control of comorbid conditions.