Survival, effect measures, and impact numbers after dementia diagnosis: a matched cohort study

Background: Knowledge on survival after diagnosis is important for all stakeholders. We aimed to estimate the survival and life expectancy after a dementia diagnosis, and to quantify the impact of dementia subtypes on mortality. Methods: Retrospective matched cohort study using a linkage between a dementia-specific registry and two primary care electronic medical records databases. Between 1 January 2007 and 31 December 2015 there were 5,156 subjects aged 60 years and over registered by the Registry of Dementia of Girona and matched to 15,468 age-sex and comorbidity individuals without dementia attended by general practitioners in the province of Girona (Catalonia, Spain). Results: The median survival was 5.2 years (95% CI 5.0 to 5.4), the median life expectancy was 74.7 years (95% CI 71.9 to 76.5), and there were differences by gender. The mortality rate was 127.1 per 1,000 person-years (95% CI 121.6 to 132.7), and the hazard ratio for mortality in persons with dementia ranged between 1.63 (95% CI 1.52 to 1.76) for Alzheimer's disease and 2.52 (95% CI 1.90 to 3.35) for Parkinson-plus syndromes. There was one death per year attributable to dementia for every 18.6 persons with dementia, and for every 2.4 persons with dementia who die, one death was attributable to dementia. Conclusion: The prognosis after dementia diagnosis is conditioned by demographic and clinical features. Although survival is larger for women, they also experience a higher number of years of life lost. Parkinson-plus syndromes and dementia due to multiple etiologies are among the most malignant subtypes regarding mortality.