One Direction back Alzheimer's charity for Louis Tomlinson's girlfriend

One Direction have raised nearly $2,000 for an Alzheimer's charity in support of Louis Tomlinson's girlfriend as her grandfather battles dementia.

The boyband stars donated a signed T-shirt to an eBay.com auction to raise money for British organisation the Alzheimer's Society, a care and research charity for those suffering the degenerative condition as well as other forms of dementia.

The singers threw their support behind the organisation after Tomlinson's girlfriend, Eleanor Calder, discovered her grandfather has been diagnosed with dementia.

Calder says, "I'm so pleased the boys have decided to support Alzheimer's Society in this way. My grandfather has dementia and my family and I have had first hand experience of how the condition affects every aspect of a person's life."

Jenny Hughes, chief executive of the Alzheimer's Society, adds, "The boys' support will help us reach new audiences and raise awareness of dementia amongst younger people. Everyone has a role to play in improving the lives of people with dementia."

The T-shirt sold for $1,952 on Thursday (20Dec12).