In November 2010, when I was 25 years old, I moved in with a man who was 98. This man, whom I'll call Mr Schecter, wasn't a friend or relation or anyone I knew. He was a Holocaust survivor in the first stages of dementia, and I'd been hired to look after him. Although my background was in clinical psychology, I was by no means a professional caregiver. I was employed because Mr Schecter's son – I'll call him Sam – had seriously underestimated his father's condition. Sam's mistake was understandable. The most obvious paradox of dementia is the victim's frequent inability to recognise it, and Mr Schecter went about his life as though burdened by the normal aches and pains of aging rather than by an irrevocable and debilitating illness. If he put the laundry detergent in the oven or forgot which floor he lived on, he'd shake his head and sigh, Mayn kop arbet nisht ("my head doesn't work"). But it was a lament, not a diagnosis. And this denial, both clinical and profoundly human, led Sam to misjudge the illness as well.
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http://www.theguardian.com/society/2015/oct/20/the-deviousness-of-dementia?