Difficulty identifying common smells such as cinnamon, lemon, and banana could signal the onset of Alzheimer's disease, according to a study published in the Archives of General Psychology this month.

Such tests could be invaluable if scientists are able to develop the capability to slow or stop the disease's progression. Alzheimer's has no cure and effects approximately 4.5 million Americans, according to the National Institute on Aging.

The study measured the odor identification capabilities of 589 elderly persons during the course of five years. They found that only about 1 percent of those with a strong sense of smell developed mild cognitive impairment, a precursor to Alzheimer's, while half of those in the 25th percentile developed symptoms.

However, lead author Robert Wilson of Chicago's Rush University Medical Center told the Associated Press that people experiencing a weakening sense of smell shouldn't panic. "Not all low scorers went on to have cognitive problems," he said.