"Either bacteria are not involved or we could not discern their effects, " said Dr Strandberg.

BBC: Herpes virus linked to dementia

"Inflammation has been implicated in dementia and viral infections could be a triggering factor, " said Dr Strandberg.

BBC: Herpes virus linked to dementia

Ake Strandberg, the hospital's chief executive, says it offers cheaper care than its competitors, and is the only hospital in Sweden to publish detailed quality indicators.

ECONOMIST: Health: Stockholm syndrome | The