Objectives: To provide estimates of survival after onset of dementia by age, sex, self reported health, disability, and severity of cognitive impairment.
Design: Analysis of participants from prospective population based cohort study in 1991-2003, with follow-up of dementia status in all individuals after two and six years (in one centre) and 10 years and in subsamples additionally at six and eight years and mortality until 2005.
Setting: Multicentre population based study in England and Wales: two rural and three urban centres.
Participants: 438 participants who developed dementia from a population based study of 13 004 individuals aged 65 years and over drawn from primary care population registers.
Main outcome measures: Sociodemographic factors, cognitive function, specific health conditions, and self reported health collected at each interview. Cox's proportional hazards regression models were used to identify predictors of mortality from the selected variables in people who received diagnosis of dementia according the study's criteria.
Results: By December 2005, 356 of the 438 (81%) participants who developed dementia during the study had died. Estimated median survival time from onset of dementia to death was 4.1 years (interquartile range 2.5-7.6) for men and 4.6 years (2.9-7.0) for women. There was a difference of nearly seven years in survival between the younger old and the oldest people with dementia: 10.7 (25th centile 5.6) for ages 65-69; 5.4 (interquartile range 3.4-8.3) for ages 70-79; 4.3 (2.8-7.0) for ages 80-89, and 3.8 (2.3-5.2) years for ages > or =90. Significant factors that predicted mortality in the presence of dementia during the follow-up included sex, age of onset, and disability.
Conclusion: These analyses give a population based estimated median survival for incident dementia of 4.5 years. Such estimates can be used for prognosis and planning for patients, carers, service providers, and policy makers.