Is the prevalence of dementia declining?
A new study has been making headlines this week reporting:
Dementia rates among people 65 and older in England and Wales have plummeted by 25 percent over the past two decades, from 8.3 percent to 6.2 percent. Another recent study, conducted in Denmark, found that people in their 90s who were given a standard test of mental ability in 2010 scored substantially better than people who had reached their 90s a decade earlier.
So do we need to still be concerned about rising dementia numbers? Yes! It’s important to read between the lines. Alzheimer Society of Canada’s Scientific Advisor, Dr. Larry Chambers clarifies:
The investigators studied dementia that included Alzheimer’s disease, dementias due to vascular disease and other dementias. Because vascular disease is included in their estimates, the investigators believe the observed reduction in dementia is due to reductions in cardiovascular disease, strokes and heart attacks that can cause cognitive impairment.
Over the last 15 years, the prevalence of heart disease and in particular, strokes, has declined significantly. These decreases are attributed to prevention activities including better blood pressure control, improved lifestyle (physical activity and healthier diet) and effective treatments of heart disease.
But dementia remains a chronic disease that, for most people, occurs late in life. As baby boomers reach 65 years and our population continues to age, the UK investigators point out that the number of people with dementia will continue to grow and with it, so will the challenges to society.
It’s true that some kinds of dementia, such as vascular dementia, which can be caused by lifestyle factors and environment, are declining in percentage of growth. This is because as we eat better and live healthier lives, so the instances of heart attack and stroke, two factors that can cause cognitive impairment, are reduced.
Further commentary from The Lancet notes:
If positive changes in health behaviour can decrease prevalence of dementia, then negative lifestyle choices might promote, rather than prevent, dementia. The cohorts of people who have been developing dementia in the past 30 years lived through periods of austerity during which diet was often controlled and this might have protected them in the balance of risk.
This was not the case for present cohorts entering the period of risk for dementia (ie, those aged >60 years). It is plausible that the present epidemic of morbid obesity, with consequent cardiovascular disorders, stroke, and diabetes, might act to increase the proportion of people with dementia in future cohorts.
This is why it is so important to continue to make brain healthy lifestyle choices.
However, it’s important to note the number of people across the globe with dementia is climbing, and as baby boomers age, dementia is becoming a health crisis. The Lancet still echos the World Health Organization’s 2012 report, that even with a small decrease in incidence and prevalence, population aging will still double the numbers with dementia worldwide in the next generation.