Women who have five or more children are at far greater risk of developing Alzheimer’s disease, new research suggests.

The study involving 3,549 women also found the risk of developing the neurodegenerative disease in later life is halved for women who have had an abortion or miscarriage.

The disease affects women more than men and researchers believe the findings may show a way of halting the condition early, by giving women hormone treatments.

Professor Ki Woong Kim, of the Department of Brain and Cognitive Sciences at Seoul National University College of Natural Sciences in Seoul, South Korea, said: "It's possible that the modestly raised levels of oestrogen in the first trimester of pregnancy are within the optimal range for protecting thinking skills.

"Oestrogen levels double by the eighth week of pregnancy before climbing to up to 40 times the normal peak level.

"If these results are confirmed in other populations, it is possible that these findings could lead to the development of hormone-based preventive strategies for Alzheimer's disease based on the hormonal changes in the first trimester of pregnancy."