As recently as 1987, caged canaries were used as sentinels in British coal mines to warn miners of poisonous gas. Birds are more sensitive to them than we are, so they can suffer before the gas reaches levels dangerous to humans, allowing miners to avoid evacuation and suffocation.
The sense of smell is the canary in the coal mine of human health, according to new research. A study published today in the journal PLOS ONE shows that losing your sense of smell is a good predictor of death within five years, suggesting that the nose knows when it’s dying, and that smell is a bellwether for a person’s overall state. as a marker of exposure to body or environmental toxins.
The study included more than 3,000 participants aged 57 to 85 from the National Social Life, Health, and Aging Project (NSHAP), a longitudinal study of factors affecting well-being among older Americans.
In 2005–2006, Jayant Pinto of the University of Chicago and his colleagues asked all participants to perform a simple test to identify five common odors (rose, leather, fish, orange, and mint) using the number of misidentified odors. by odor severity score.
Five years later, the researchers wanted to identify as many participants as possible and conduct this odor test a second time. During the five-year interval between the two trials, 430 of the original participants died (that’s 12.5% of all participants). Of these, 39% of those who failed the first olfactory test died before the second test, compared to 19% of those with moderate loss of smell at the first test, and only 10% of those with a healthy sense of smell.
In other words, participants who failed the initial olfactory test were four times more likely to die within five years than those who correctly identified all five odors. This was true when controlling for other factors that influence smell, such as race, gender, mental illness, and socioeconomic status, and mild smell loss was associated with a slightly increased likelihood of impending death.