Difficulty identifying common smells such as lemon, banana and cinnamon may be the first sign of Alzheimer’s disease, according to a study that could lead to scratch-and-sniff tests to determine a person’s risk for the progressive brain disorder.

Such tests could be important if scientists find ways to slow or stop Alzheimer’s and the severe memory loss associated with it. For now, there’s no cure for the more than 5 million Americans with the disease.