Older adults with a poor sense of smell may be sooner than their counterparts who have keen olfactory abilities, and US study suggests.
Researchers asked 2,289 adults, ages 71 to 82, to identify 12 common smells, awarding scores from zero to as high as 12 based on how many scents they got right. When they joined the study, none of the participants were frail: they could walk a quarter mile, climb 10 steps, and independently complete daily activities.
During 13 years of follow-up, 1,211 participants died.
Overall, the weak nose was 46 percent more likely to be 10 years old and 30 percent more than 13 years later than people with good sense of smell, the study found.
"The association was largely limited to those who reported good-to-excellent health at enrolment, suggesting that poor sense of smell is an early and sensitive sign for deteriorating health before it is clinically recognisable," said Dr. Honglei Chen of Michigan. State University in East Lansing.
"Poor sense of smell is likely to be an important health marker in older adults beyond what we have already known about (ie, connections with dementia, Parkinson's disease, poor nutrition, and safety hazards)," Chen wrote.
People who started out of the study in good or good health were 62 percent more likely to be 10 years old when they had a bad sense of smell than when they had a nose, a research report in the Annals of Internal Medicine.
But smell did not appear to make a meaningful difference in mortality rates for people who were in fair to poor health at the start of the study.
With poor sense of smell, people were more likely to die of neurodegenerative and cardiovascular diseases, but not of cancer or respiratory conditions.
Poor sense of smell may be early warning for poor health in older age that goes beyond neurodegenerative diseases that are often signaled by the beginning of physical or mental decline, the results also suggest.
'Bellwether for Declining Health'
Dementia or Parkinson's disease was only explained by 22 percent of the higher death risk tied to the poor sense of smell, while the weight loss explained just six percent of this connection, researchers estimated. That leaves more than 70 percent of the higher mortality rates tied to a weak nose unexplained.
The connection between the poor sense of smell and mortality risk was not found to be different from sex or race based on individuals' demographic characteristics, lifestyle, or chronic health conditions.
One limitation of the study is that the older adult participants were relatively functional, making it possible for the younger people or for the elderly to work, the study team writes.
Researchers also only tested smell at one point in time, and they did not look at whether or not they changed their abilities over time. Researchers also lacked data on certain medical causes of weak nose such as nasal surgery or chronic rhinosinusitis that are not related to aging.
"The take-home message is a loss in the sense of being served as a bellwether for declining health," said Vidyulata Kamath of the Johns Hopkins University School of Medicine in Baltimore, co-author of an accompanying editorial.
"As we age, we may be unaware of declining olfactory abilities," Kamath said by email. "Given this discrepancy, routine olfactory assessment in older adults may have clinical utility in screening persons at risk for illness, injury or disease for whom additional clinical work-up and / or intervention may be warranted."