This is part 5 of a series of lessons in brain health from our elders — those folk who lived the longest and healthiest.
The 2015 World Alzheimer Report on the global impact of dementia states there are over 9.9 million new cases of dementia each year worldwide, which implies one new case every 3.2 seconds.
In 2015, the estimated number of people living with dementia was 22.9 million in Asia, 10.5 million in Europe, 4 million in Africa, and 9.4 million in the Americas. As baby boomers reach older age, numbers are set to double every twenty years.
The statistics made for disturbing reading and the 2015 report on dementia sums up how many of us feel:
Dementia is highly stigmatised and universally feared. It is often perceived as a normal part of ageing, and that no actions can be taken to prevent or treat it.
Although stats vary by country, your absolute risk is probably not as high as you fear.
In the UK, about two in 100 (two per cent) of people aged between sixty-five to sixty-nine have dementia; this figure rises to one in five (twenty per cent) for those aged between eighty-five to eighty-nine.
The majority of centenarian studies report rates of dementia in the extremely old as sitting somewhere between forty-five and sixty-five per cent, with the Sydney Centenarian Study finding rates are consistent with this finding.
On the upside, eighty per cent of people in their eighties, and nearly half of centenarians remain dementia-free.
So contrary to popular belief, dementia is not a natural or inevitable consequence of ageing.
Dementia is a disease, and while there is no cure, there are steps you can take to tip the brain health scales in your favour.
In late 2015, an international team pooled data from 323 studies including over 5000 people and ninety-three identified factors thought to influence risk for Alzheimer’s disease, many of which also increase the risk for cardiovascular disease. The most significant harm was heavy smoking, whereas healthy diet was protective.
A total of nine modifiable harms were identified that caused sixty-six per cent of AD cases globally.
For men and women the 9 modifiable risk factors for AD were:
- Being obese
- Carotid atherosclerosis (hardening of the arteries)
- Type 2 diabetes
- Low education (not completing secondary school)
- High total homocysteine level
- High blood pressure
Interestingly for women, oestrogen therapy, which included the oral contraceptive pill or hormone replacement therapy, protected against AD.
The paper concluded with a startling statement:
Two in three dementia cases worldwide are preventable.
More women than men develop Alzheimer’s or other dementias.
In September 2017, the Australian Bureau of Statistics (ABS) released a report stating dementia is the leading cause of death among Australian women. For men, dementia took out number two spot, right behind heart disease. The ABS warn that as treatments for heart disease improve, and men live longer, healthier lives, dementia will likely surpass heart disease as the leading cause of death for men too.
There are a number of potential biological and social reasons for this fact.
One prevailing view that, on average, women live longer than men, and getting older is the greatest risk factor for AD. Or to put it simply – there are more older women alive than old men, so there are more cases of AD.
A related reason is men’s ‘survival bias’. Men have higher rates of cardiovascular disease and stroke than women, so those men who live to old age tend to be much healthier than women of the same age and therefore have lesser risks of developing AD.
Another well-known genetic risk factor for AD is the gene APOE-e4. A 2017 meta-analysis of nearly 58,000 people found women with particular versions of the APOE-e4 may be more likely to develop AD than men, but only between the ages of ages 65 and 75 years.
One final reason often given to account for the sex difference in risk is low education in women. The more years schooling you received, the lower your risk of developing AD, and the fact women born before the 1950s completed fewer years schooling than men may have rendered their brains more vulnerable to the disease.
We are privileged to live in a world where life expectancy is increasing; and the ageing population, which worries so many people, is actually one of humanity’s greatest achievements.
Dementia has become humanity’s brain health problem.
This is part 4 of a series of lessons in brain health from our elders — those folk who lived the longest and healthiest.
About Dr Sarah
I’m an Oxford University-educated neuroscientist, presenter of ABC Catalyst, director of The Neuroscience Academy, and author of The Women's Brain Book. The neuroscience of health, hormones and happiness.
download my free checklist
9 Daily Habits of Highly Healthy Brains
Learn how to use neuroscience in your everyday life.