Pre-dementia 'more common in men than women'
Although dementia is more common in women, it appears that men are at higher risk of the earliest signs of the disease, according to latest research.
It's unclear why more men avoid full-blown disease, but understanding this might be key to beating dementia, Archives of Neurology reports.
Ultimately, it may even reveal a way to halt dementia, experts hope.
The US investigators tracked the health of nearly 1,500 elderly men and women over a three-year period.
During this time far more of the men developed mild cognitive impairment - 72 in every 1,000 compared to 57 per 1,000 women.
The Mayo Clinic researchers considered several factors that might have skewed the results, such as age, education and marital status, but found the gender difference persisted.
They say more work is now needed to understand if and how men might be somewhat resilient to dementia.
Dr Marie Janson, of Alzheimer's Research, UK said: "These surprising results suggest that men may be at greater risk for MCI (mild cognitive impairment) despite having a lower risk for dementia, and it will be important to see whether further studies can replicate these findings.
"A key goal for research is to identify why some people with MCI develop dementia while others don't. If we can understand why some people have a greater risk for cognitive decline and dementia, we stand a better chance of being able to prevent the condition.
"With 820,000 people affected by dementia, and a rapidly ageing population, the need for research to find new ways to treat and prevent the condition has never been more urgent."
It might simply be that fewer men live to reach an age when their dementia will become more advanced. It is well known that, on average, women tend to outlive men.
But some scientists believe the difference could be explained by gender alone.
For example, studies have shown a person's sex can influence how exercise benefits the body and mind.
In women, exercise is associated more with a mortality benefit, whereas in men, the positive effect of exercise is more of a cognitive improvement.
In an accompanying editorial, Dr Kenneth Rockwood of Dalhousie University in Canada, said: "For some men, MCI represents incomplete disease expression; alternately, they resist dementia development more.
"MCI in men could lend some insight into what prevented dementia might look like."
Professor Derek Hill, of University College London, said: "By the time people get clinical dementia, it may well be too late to treat them.
"This study shows that MCI is a very complicated mix of factors, and that different types of MCI arise and progress quite differently.
"This information could be important in improving diagnosis to identify patients who will benefit from current or future treatments."