Many factors influence survival rate of dementia patients

Individuals diagnosed with dementia will survive an average of four and a half years. Many factors, however, can influence longevity, a study out today reports.

Scientists from Cambridge examined a number of factors that may affect life expectancy for people diagnosed with dementia. They hope that better information about the different factors that influence longevity will be valuable to patients, carers, and policy-makers.

Dr Fiona Matthews, at the Medical Research Council's Biostatistics Unit, said: “Currently, clinicians give a rough single estimate when someone is diagnosed with dementia. However, we have found that a number of factors can influence how long an individual will live. It is important for these to be taken into account when planning long term care and support for the patient.”

The number of people affected by dementia is estimated to double every 20 years to 81 million by 2040. As dementia is a major cost to health care and social systems in the developed world, it is important to understand the causes and course of the disease in order to make informed decisions.

The study, led by Professor Carol Brayne at the Cambridge University Department of Public Health and Primary Care, found that survival from the estimated onset of dementia was 4.6 years for women and 4.1 years for men.

Age, sex and whether the individual had a disability prior to diagnosis affected survival rates. There was nearly seven years difference in survival rates between the youngest and the oldest people with dementia (10.7 years for those aged 65-69 and 3.8 years for those aged 90 or over). Additionally, there was around a three year reduction in survival between the most and the least disabled at onset, suggesting that the frailer individuals are at higher risk (even after age is taken into account).

Interestingly, social class, marital status and living accommodations (such as whether the individual lives in a nursing home) did not influence mortality rates.

“There is still much to learn about life expectancy and dementia,” said Professor Brayne. “Our next study will look at whether the next generation shows the same patterns of dementia as this study, as many factors in educational levels, lifestyles, health and health care have changed.”

Professor Clive Ballard, Director of Research at the Alzheimer's Society, said: “When a person is diagnosed with dementia there isn't a crystal ball to tell what the future holds. However this study, which takes into account people's ages, backgrounds and general health is the most accurate UK study yet that may help us estimate how much longer that person with dementia may enjoy a good quality of life.

“This is important as it could help people plan and budget effectively for the future and give people access to the right treatments and care services.”

The Medical Research Council's cognitive function and ageing study (MRC CFAS) is a multicentre, longitudinal, prospective population based epidemiological study of cognitive function and disability in the UK.