"The work of Professor Williams and colleagues shows how British researchers lead the world in the struggle to understand and defeat dementia. With the right support for scientists, we can offer hope to the 30 million people worldwide who live with dementia.

The First Minister for Wales, Rhodri Morgan, said: "This major breakthrough in the battle to understand and develop treatments for Alzheimer's is good news for the 37,000 people in Wales and their carers who are affected by Alzheimer's or other forms of dementia. It is a real feather in the cap of Welsh science that this important global study has been led by a Welsh scientist, Professor Julie Williams and that the Welsh Assembly Government was able to give financial support for her work. World-class research like this will help lead to improved treatment for this distressing disease, and may one day even mean we can cure dementia."

Sir Leszek Borysiewicz, Chief Executive of the Medical Research Council, said: "Funding work on neurodegenerative diseases is a priority for us and MRC investment in this kind of innovative research is crucial in piecing together the Alzheimer's puzzle. This study is a huge step towards achieving an earlier diagnosis of Alzheimer's and improving the lives of the many people affected by the disease."

The team shared their data with a further French-led study, also published in Nature Genetics, which has revealed compelling evidence for a third gene associated with Alzheimer's called CR1.

The only other genes that have been connected to Alzheimer's disease are in extremely rare cases of familial Alzheimer's disease, which is inherited in less than 1% of cases.

Source: Alzheimer's Research Trust