A Columbia University psychiatrist has developed a simple smell test that he says can predict with a high degree of certainty whether a senior will die within four years.

A study of the test, reported in the Annals of Neurology, found that older adults who had a hard time identifying certain odors had a much greater risk of dying within a few years than those who could detect those scents.

Nearly half (45 percent) of the 1,169 individuals in the study who had the lowest scores on the 40-item smell test died within four years, on average, compared with 18 percent of participants with the highest scores.

The Medicare beneficiaries scratched and sniffed individuals odorant strips and chose the best answer from four items listed as multiple-choice.

"The increased risk of death increased progressively with worse performance in the smell identification test and was highest in those with the worst smelling ability, even after adjusting for medical burden and dementia," said lead researcher Davangere Devanand, M.D., a professor of psychiatry and neurology at Columbia University Medical Center.

"This was a study of older adults — the question that remains is whether young to middle-aged adults with impaired smell identification ability are at high risk as they grow older."

Loss of sense of smell is a known factor in dementia and Alzheimer’s disease, health experts say, noting it may indicate a significant decline in brain function.