Biology of Humans 6th Edition by Judith Goodenough,Betty McGuire

Exercise 17

Most people think of smell as the least important sense. However, researchers report that a decreased ability to identify odors can predict death within 5 years. The following quotations are excerpts from the University of Chicago News.1 The entire article can be found at http://news.uchicago.edu/article/2014/10/02/decreased-ability-identify- odors-can-predict-death According to this study,2 "For older adults, being unable to identify scents is a strong predictor of death within five years.... Thirty-nine percent of study subjects who failed a simple smelling test died during that period, compared to 19 percent of those with moderate smell loss and just 10 percent of those with a healthy sense of smell. "The modified smell tests used 'Sniffin' Sticks' odor-dispensing devices that resemble a felt-tip pen but are loaded with aromas rather than ink. Subjects were asked to identify each smell, one at a time, from a set of four choices. The five odors, in order of increasing difficulty, were peppermint, fish, orange, rose and leather. "When the researchers adjusted for demographic variables such as age, gender, socioeconomic status (as measured by education or assets), overall health and race, those with greater smell loss when first tested were substantially more likely to have died five years later. Even mild smell loss was associated with greater risk. "'We think loss of the sense of smell is like the canary in the coal mine,' said the study's lead author Jayant M. Pinto, an associate professor of surgery at the University of Chicago who specializes in the genetics and treatment of olfactory and sinus disease. 'It doesn't directly cause death, but it's a harbinger, an early warning that something has gone badly wrong and that damage has been done. Our findings could provide a useful clinical test, a quick and inexpensive way to identify patients most at risk.'"
Develop some hypotheses to explain the possible causes for a relationship between loss of smell and death within 5 years.