New research shows that high levels of oestrogen in men may be linked to dementia.
A prospective study carried out by researchers in Utrecht has found an association between higher oestrogen levels in older men and an increased risk of dementia.
Further findings suggest that the parallel effect is not true: levels of testosterone were not linked with cognitive decline.
The findings appear to differ from a large-scale study carried out recently in Minnesota, which found that women whose ovaries were removed were more vulnerable to dementia or cognitive impairment.
As these are fairly new areas of study, the researchers were reluctant to draw confident conclusions.
"Our findings of an increased risk of cognitive decline and Alzheimer's disease associated with higher oestradiol are similar to recent findings in postmenopausal women," the report concludes.
"Further studies are needed to examine whether there are mechanisms by which oestradiol may increase risk of cognitive decline and dementia."
Dementia is on the increase across the world. It has been estimated that 13 million people in America alone will have the disease by 2050 due to the world's ageing population.