The Decline of Dementia

Currently, many places in the world have an ageing population. This means there is an increase in the average age of the population and an in the number and proportion of older people in the population.  Over the 40 year period 1974 to 2014, the median age of the UK population has increased from 33.9 years to 40.0 years. Similarly in the US in 2013 people aged 65 or older represented 14.1% of the population and it is predicted this will double by 2060.

With the ageing population, diseases which occur in older people such as dementia are a concern. Worldwide, the World Health Organization (WHO) estimates that 47.5 million people have dementia in the world and the total number of people with dementia is projected to reach 75.6 million in 2030 and almost triple by 2050 to 135.5 million.

However, this week in the New England Journal of Medicine findings are presented which suggests that the rates of dementia may actually be decreasing.

Researchers used data from the Framingham Heart Study (FHS) in which the participants (5,205 people) have been monitored for the occurrence of cognitive decline and dementia since 1975. Using a consistent set of criteria the FHS researchers have been able to diagnose Alzheimer’s disease and other dementias over the last 30 years.

In the study the team, led by Dr. Sudha Seshadri, the Professor of Neurology at Boston University School of Medicine, looked at four distinct periods in the late 1970s, late 1980s, 1990s and 2000s. They found that there was a progressive decline in incidence of dementia at a given age, with an average reduction of 20 percent per decade since the 1970s.

The limitation of the data set is that the population is mostly of European ancestry. Therefore further studies are needed to see if the findings also apply to other populations.

Nevertheless, the results are still important as they demonstrate that some dementia cases may be preventable or delayed.

Photo: Flickr, Ann Gordon