1.2m people in England and Wales predicted to have dementia by 2040

The research, published in The British Medical Journal (BMJ), shows that, although the incidence (number of newly diagnosed cases) of dementia is falling, the overall prevalence (number of people living with the condition) is set to increase substantially as people live longer and deaths from other causes, such as heart disease, continue to decline.

With current costs of dementia to the UK economy estimated at £23 billion a year, accurate projections are vital in defining future needs. But existing forecasts may not be precise as they assume that rates of dementia will remain constant.

Future burden

An international team of researchers set out to predict the future burden of dementia with more certainty by developing a mathematical model (IMPACT -- Better Ageing Model) that takes account of disease trends and death rates alongside the effects of increasing life expectancy.

They used data from 18,000 men and women from the English Longitudinal Study of Ageing (ELSA) -- a study which began in 2002 to track the health of a representative sample of the population in England aged 50 and older.

Participants were selected randomly in six waves from 2002 to 2013. At each wave, tests were carried out to assess memory, verbal fluency and numeracy function, and basic activities of daily living (e.g. getting in or out of bed, dressing and eating). Dementia was identified by the abovementioned assessments, complemented by interviews with carers, or by diagnosis by a doctor.

Substantial increase

After accounting for the effect of dropout from the study, the team found the rate of dementia incidence goes down by 2.7% per year between 2002 and 2013.

Despite this decline in incidence, the model shows that overall prevalence of dementia is set to increase substantially -- mainly due to increased life expectancy.

Based on these calculations, the researchers estimate there are currently 800,000 people living with dementia in England and Wales and the number will increase to over 1.2 million by 2040.

Professor in Public Health and Policy Martin O'Flaherty from the University of Liverpool's Institute of Psychology, Health and Society, said: "This study highlights the fact that although new cases are falling the overall burden will rise mainly due to people living longer.

"Current and future policy makers should take note of these figures as they will have a significant impact on the costs of dementia to the UK economy and our ability to treat and care those affected."

Public health efforts

Dr Sara Ahmadi-Abhari, lead author from University College London, says: "The risk of developing dementia at any given age is going down over time, shifting dementia to later years in life. This decline is mainly because of adopting healthier lifestyles, and also improvements in healthcare.

"Our estimate of 1.2 million people with dementia by 2040 is based on the assumption that the decline in risk of developing dementia continues to the future. If public health efforts fail and the risk of developing dementia does not continue to decline, the growth in numbers of people living with dementia will be much larger, reaching 1.9 million by 2040."

The study also confirms that high quality epidemiological studies are still needed to monitor actual changes in dementia prevalence, incidence, and associated mortality over time, he adds.