My elderly and increasingly frail father was in hospital for three weeks before Christmas after several falls in the space of a few days. He broke his hip three years ago and has never recovered properly - his mobility had been deteriorating for several years before that but the fracture seemed to be a tipping point. He can only get around very slowly with a walking frame and he shuffles rather than walks. He's very prone to falls and is extremely weak and barely eats anything - usually just things like soup or yogurt.
We've noticed that his cognitive abilities have been declining markedly over the last few months but everyone's assured us there's nothing wrong. He's also become profoundly deaf and we can now only communicate by writing everything down on a whiteboard.
While he was in hospital he was given the Addenbrooke's cognitive test and scored 65 out of a possible 100, with particular difficulties with short term memory and executive planning. Dr Google tells me that's not good 
Does anyone have any experience of how according the test is and if he does have some sort of dementia what kind of timeframe are we looking at? He's nearly 91 and heart, lungs etc all fine