“In patients with Lewy body disease, happiness was kept unaffected by aging, age of onset, duration of the disease, cognitive function, and apathy; however, recognising the facial expression of fear was difficult.
“In addition, due to ageing, cognitive decline, and apathy, the facial expression recognition ability for sadness and anger decreased.”
The study found that in particular, cognitive decline reduced recognition of all of the facial expressions except for happiness.
It concluded: “There were several facial expressions that the Lewy body disease patients were unable to accurately identify.”