At any given time, two-thirds of all dementia patients are of just one gender.
This is a widely established fact.
But why is this gender so much more affected by dementia than the other? That’s the subject of a new study published in the journal JAMA Network Open.
It was once believed that more women suffer from dementia than men simply because women tend to reach higher ages than men by the time they die. But researchers at the University of Michigan have started to question whether there is more to this imbalance—especially considering that women make up a staggering two-thirds of dementia patients at any given time.
To solve the mystery, the researchers obtained information first collected in several large population-wide studies, including the Atherosclerosis Risk in Communities Study, the Coronary Artery Risk Development in Young Adults Study, the Cardiovascular Health Study, the Framingham Offspring Study, and the Northern Manhattan Study.
Only people who reported black or white racial identities were included in the study because the research samples did not include enough people of other races to reach definite conclusions about them. This left the researchers with a sample of 26,088 people: 11,775 men and 14,313 women.
These subjects were tested on their global cognition (the ability to learn and understand concepts), executive function (a person’s control over their behavior and decisions), and memory when they were 58 years old and then repeatedly assessed on the same characteristics over the next eight years in order to record their rate of neurological decline.
At the beginning, women tested higher on all three dimensions: 2.20 points higher for global cognition, 2.13 points higher for executive function, and 1.89 points higher for memory.
But while men and women suffered approximately the same rate of decline in memory, women’s global cognition declined by 0.07 points per year faster than that of men, and their executive function by 0.06 points per year faster.
So, what can one conclude from these findings?
The most common conclusion is that women have a higher cognitive reserve than men. Cognitive reserve is the brain’s ability to compensate for neural damage by using alternative strategies to complete cognitive tasks that were once completed in conventional ways. People with higher education levels have also been found to have higher cognitive reserve.
In the 1980s, scientists found through autopsies that many people with no symptoms of dementia had brain damage similar to that seen in people with advanced Alzheimer’s disease. They concluded from this that, while all people’s brains seem to suffer similar damage, some are better at compensating for that damage.
At first glance, this seems like a positive finding, but its downside can be seen among women in this latest study. Women start with a higher cognitive reserve, but once this is depleted, their decline in cognition is faster than that of men with lower cognitive reserve.
In other words, women probably develop dementia at the same age that men do, but the disease goes undiagnosed because women’s high cognitive reserve enables them to continue performing well on cognitive tests.
Delayed diagnoses of dementia result in delayed—and therefore less effective—treatment for women. This is the increased dementia risk that women face.
In response to this, the researchers propose developing more sensitive cognitive tools to enable an earlier diagnosis of dementia in women.