Men are more likely to develop Alzheimer's if they have a stroke, while women are more at risk if they are depressed, research suggested today.

A low level of education is also thought to influence the chance that both sexes will develop the disease.

A study of almost 7,000 people over the age of 65 examined a range of environmental and health factors to see how they affected progression of dementia.

None of the people had dementia at the start of the study but 2,882 (42%) were classed as having mild cognitive impairment (MCI).

This means they were starting to show signs of decline and did not perform highly on tests examining their level of recall.

The group, drawn from the French cities of Bordeaux, Dijon and Montpellier, was followed up after two years and again two years later.

Men and women with MCI were more likely to be depressed and to be taking anticholinergic drugs, which are used to treat a range of conditions including incontinence, travel sickness and stomach cramps.

Recent research has suggested some of these drugs, which are also an older treatment for Alzheimer's, can cause elderly people to experience greater decline in their thinking skills.

Today's study said men with MCI "were also more likely to have a higher body mass index, diabetes and stroke, whereas women were more likely to have poor subjective health, to be disabled, to be socially isolated, and to suffer from insomnia.'' Of those with MCI, 189 (6.6%) developed dementia over the next four years, 1,626 (56.5%) remained with a diagnosis of MCI, and 1,067 (37%) returned to normal levels of functioning.

A total of 8% men with MCI developed dementia compared with 6% of women.

Most (122) cases of dementia were of Alzheimer's disease, 19 were vascular dementia and the rest were other types.

The study found that the main risk factor for men going on to develop dementia was a variation in the ApoE gene, known to influence progression of the disease.

The second highest risk factor was having a stroke, with men 2.8 times more likely to develop dementia if they had suffered one.

Men with a low level of education were also 2.3 times more likely to develop dementia.

Meanwhile, women with the ApoE gene were 2.3 times more likely to develop dementia and twice as likely to develop it if they had a low level of education.

They were also twice as likely to develop dementia if they had depression.

The authors said: "Some potentially reversible risk factors for progression to dementia were identified, which were not the same for men and women (notably stroke in men and subclinical depression and use of anticholinergic drugs in women).

"These factors should be taken into account in the development of gender-specific clinical intervention programmes for MCI.'' The study was published ahead of print in the Journal of Neurology, Neurosurgery and Psychiatry.