A poor sense of smell could be an early warning sign of dementia, according to a new study.
An inability to identify odors has previously been linked with a higher risk of premature death. This new study found that those who could not name at least four out of five common smells were more than twice as likely as those with a normal sense of smell to develop dementia within five years.
The five scents used in the study, which involved 3,000 adults ages 57 to 85, were peppermint, fish, orange, rose and leather.
Some 78 percent of those tested could name at least four of the five scents presented, and so had a normal sense of smell. Fourteen percent could identify just three smells. Five percent could name only two, while 2 percent could name just one, and 1 percent couldn’t determine any of the smells.
Five years after the test, almost all of those who were unable to identify a single scent had been diagnosed with dementia. Nearly 80 percent of those who provided only one or two correct answers also suffered from dementia.
“These results show that the sense of smell is closely connected with brain function and health,” said the study’s lead author, otolaryngologist Jayant M. Pinto, in a written statement. “We think smell ability specifically, but also sensory function more broadly, may be an important early sign, marking people at greater risk for dementia.
“We need to understand the underlying mechanisms,” Pinto added, “so we can understand a neurodegenerative disease and hopefully develop new treatments and preventative interventions.”
Pinto emphasized that the smell test only marks someone for closer attention and that much more work would need to be done to determine whether a smell test could be a reliable diagnostic test.
A paper describing the long-term study was published in the Journal of the American Geriatrics Society.
Another study published this year that also looked at one’s sense of smell associated the inability to identify odors with an increased risk of premature death. Researchers from Stockholm University looked at adults 40 to 90 years old over a 10-year period and found that those who had lost their sense of smell had a 19 percent higher risk of early death than those with a normal sense of smell.