According to a study published in the Alzheimer's and Dementia medical journal, Alzheimer's disease affects a part of the brain that is responsible for keeping people awake, which may explain why people with this condition take so many naps.An increase in the number of naps might be one of the first symptoms to appear in patients, before memory loss. The study was conducted by researchers at the University of California.The scientists also highlighted the tau protein and its role in the development of the disease. This is not the first study to do so, but more specific research on the subject (because until now, studies have focused more on the amyloid protein) is making it possible to learn more about this protein's role in the development of this disease.Lea Grinberg, co-author of the study and professor of neurology, said: 'Our work shows definitive evidence that the brain areas promoting wakefulness degenerate due to accumulation of tau, not amyloid protein, from the very earliest stages of the disease.'Alzheimer's disease in numbersMore than 35.6 million people worldwide are affected by Alzheimer's disease, with 7.7 million new cases being diagnosed each year, and the forecasts are not optimistic. According to the WHO, the number of patients should double every 20 years, reaching 115.5 million in 2050. These alarming figures should, therefore, increase awareness about the evolution of this pathology, which is still poorly understood.