A fading sense of smell can be one of the earliest signs of Alzheimer’s disease even before cognitive impairments manifest. Research by scientists at DZNE and Ludwig-Maximilians-Universität München (LMU) sheds new light on this phenomenon, pointing to a significant role for the brain’s immune response, which seems to fatally attack neuronal fibers crucial for the perception of odors. The study, published in the journal “Nature Communications”, is based on observations in mice and humans, including analysis of brain tissue and so-called PET scanning. These findings may help to devise ways for early diagnosis and, consequently, early treatment.