A study of 3 000 older persons from ages 57 to 85 found a link with loss of smell as a predictor of mortality.
The study carried out in two sessions over 5 years tested three age group's ability to determine the smells of rose, leather, orange, fish and peppermint. The test groups were 57–64, 65–74 and 75–85 years.
Those that showed a loss of smell (Anosmic) were compared with those that had not (Normosmic) and that had some loss (Hyposmic).
In a comprehensive model that included potential confounding factors, anosmic older adults had over three times the odds of death compared to normosmic individuals (OR, 3.37 [95%CI 2.04, 5.57]), higher than and independent of known leading causes of death, and did not result from the following mechanisms: nutrition, cognitive function, mental health, smoking and alcohol abuse or frailty.— Olfactory Dysfunction Predicts 5-Year Mortality in Older Adults
Smell was chosen as a good indicator of cell renewal which is critical for maintaining health often in challenging environments.
The study found that the lower the subjects' ability to detect the five control smells, the greater the chance that the subject would not survive the following 5 years.
Allowance was made for other environmental factors and the subject's initial state of health and it still showed that the loss of smell had a high correlation with death.
Olfactory function is thus one of the strongest predictors of 5-year mortality and may serve as a bellwether for slowed cellular regeneration or as a marker of cumulative toxic environmental exposures. This finding provides clues for pinpointing an underlying mechanism related to a fundamental component of the aging process.— Olfactory Dysfunction Predicts 5-Year Mortality in Older Adults