A group of scientists claim they may have discovered why Alzheimer's disease affects more women than men.
Researchers at the Stanford Center for Memory Disorders have published a study that analyses a gene known as APOE4, NPR reports.
It has been known for a long time this gene increases the risk of developing Alzheimer's in both males and females, but the new report suggests it is more dangerous for women.
Published in the journal Annals of Neurology, the study claims APOE3 can double the chances of developing the disease in females, while it has minimal effect on men.
Michael Greicius, one of the authors of the report, said: "We believe that there is an increased risk for Alzheimer's in women and it may be that APOE4 is playing a sizeable role in this."
The gene also increases the likelihood that females will develop another condition known as mild cognitive impairment.
Michelle Mielke, a psychiatrist epidemiologist at the Mayo Clinic, said: "What is interesting in relation to this paper is that animal and cellular studies suggest that there is an interaction between APOE4 and estrogen.
"So that may possibly be explaining the findings we're seeing here in humans."
Approximately two-thirds of dementia patients in the UK are women, while that figure is similar for those with Alzheimer's disease in the US.
It is believed by many medical professionals that the fact women generally live longer than men is one of the reasons behind a higher chance of developing brain deterioration.
APOE3 has been linked to Alzheimer's since the 1990s, when it was discovered that around 50 per cent of people with the disease have it, compared to just 15 per cent of the general population.
However, this new study has found that men with the gene tend to be less likely to develop Alzheimer's than women by approximately 1.8 times.
The researchers will now attempt to determine why it acts in this way.
Find out more about Alzheimer's disease care at Barchester homes.