A number of studies have found that a poor sense of smell in older adults is linked to health problems (especially Parkinson's disease and dementia) and death. Now a recent study found that a poor sense of smell in older adults is associated with an almost 50% increase in their risk of dying within 10 years—especially in individuals reporting good health. In other words, a poor sense of smell is an early sign of deteriorating health, even when it is not apparent yet to the person.
Researchers at the Michigan State Univ. College of Human Medicine followed 2,289 persons (aged 71 to 82) for 13 years. The generally healthy persons took a smell test of 12 common odors (e.g. onion, soap, gasoline, lemon, chocolate and rose) at the start of the study, and were scored as having good, moderate, or poor sense of smell. After 13 years 1,211 of them had died. The researchers then looked to see if there was any association between scores on the smell test and their risk of death at various points over the 13 years.
No association was found at the three- or five-year mark of the study. But those with a poor sense of smell had a 46 percent higher risk of dying by 10 years and a 30 percent higher risk by 13 years, when compared with the older adults with a good sense of smell. The researchers believe the risk was lower at 13 years because so many of the participants had already died - whether their ability to smell was initially good or poor. So how to interpret the study results? It appears that a poor sense of smell may be a sensitive early sign of deteriorating health, even when it is not apparent yet.
A new Michigan State University study suggests that older adults with poor sense of smell may see an almost 50% increase in their risk of dying within 10 years—surprisingly in healthier individuals. "Poor sense of smell becomes more common as people age, and there's a link to a higher risk for death," said Honglei Chen, an epidemiologist who's focused his research on this sensory deficit in older adults.
Using data from the National Institute on Aging's Health ABC study, Chen and his research team reviewed information from almost 2,300 participants between 71 and 82 years old over a 13-year period. Participants included men and women, black and white, who completed a smell test of 12 common odors. Researchers then classified participants as having good, moderate or poor sense of smell.
Compared with older adults with a good sense of smell, those with poor smell were at a 46% higher risk for death at 10 years and 30% at 13 years. Results were minimally affected by sex, race or other demographic and lifestyle factors. However, the surprising revelation was that the healthier participants at the start of the study were found to be largely responsible for the higher risk.
Poor sense of smell is known as an early sign for Parkinson's disease and dementia and is associated with weight loss. However, these conditions only explained 28% of the increased risk, leaving most of it unexplained. "We don't have a reason for more than 70% of the increased risk. We need to find out what happened to these individuals," said Chen, who plans to pursue the mystery in future studies.