Two new studies find that a poor sense of smell is able to predict memory decline in older adults about as well as the PET scan or spinal tap.

Another study found that seniors who had the worst test scores on a smell test were 2.2 times more likely to show signs of mild cognitive decline. Olfactory cells in the nose that are responsible for a sense of smell require a constant supply of new stem cells from the olfactory bulb, a region in the forebrain. NOTE: Many other factors can lead to a poor sense of smell so other biomarkers need to be looked at in addition to sense of smell.