Poor Sense of Smell Linked to 50 Percent Higher Death Risk in Next 10 Years

Scientists studied more than 2,000 men between the age of 71 and 82 living in the U.S. for their research.

Thursday, May 2, 2019

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Poor Sense of Smell Linked to 50 Percent Higher Death Risk in Next 10 Years

Older people with a poor sense of smell could have almost double the risk of dying in the coming decade compared with those who were better at picking up odors, a study has found.

A poor sense of smell was linked to a 46 percent higher risk of dying in the next 10 years, and a 30 percent higher risk of dying in 13 years.

The research, published in the Annals of Internal Medicine, included 2,289 U.S. adults between 71 to 82 years old, who completed a smell test. The participants were asked to inhale 12 common odors, and received a point for each correct smell they chose out of four options. The team categorized the respondents as having a good, moderate or poor sense of smell according to their score, and also looked at information on the participants, including whether they smoked, drank and exercised. The researchers checked if the participants were still alive three, five, 10 and 13 years later.

By the end of the study, 1,211 of the total had died. The association between poor smell and the risk of dying was still apparent after the team accounted for factors which could skew the results, such as sex, race, and lifestyle. This link was most apparent among those with good health at the start of the study, compared to those with poor health. Of those with a poor sense of smell, 22 percent died of neurodegenerative diseases such as dementia and Parkinson's, and 6 percent were related to weight loss.

The authors wrote: “This study provides clear evidence of an association between poor olfaction and long-term mortality among older adults.

“This elevated risk can be only partially explained by dementia or Parkinson disease and weight loss, indicating that some health consequences of poor olfaction in the context of aging are unknown."

Future studies should look at a poor sense of smell as a general marker of aging to gain a deeper understanding of its health implications, they said.

Robert Howard, a professor of old age psychiatry at University College London who did not work on the paper, described it as “carefully conducted.”

“We have known for many years that loss of sense of smell in later life may precede other symptoms of neurodegenerative disorders such as Parkinson's or Alzheimer's by many years," he said. "This is because the earliest location of neuropathology in these conditions is in the olfactory system. We also know that loss of sense of smell is associated with weight loss. This is unsurprising, given the contribution of smell to our sense of taste and flavor and enjoyment of food.”

Kevin McConway, emeritus professor of applied statistics at the Open University, who was also not involved in the research, said that by researching individuals for as many as 13 years and taking a closer look at why smell might be linked to mortality, the study is a “real advance.”

But he pointed out that, as with all observational studies, it’s impossible to determine a cause behind the links, or why smell is associated with a higher death risk. It could be that a poor sense of smell is a sign of an underlying condition, or its loss could change how food tastes and lead to poor nutrition.

“There are lots of differences between the people who could smell well and those who couldn’t, apart from their sense of smell, and any differences in death rates could be due to these other differences and not to the sense of smell at all,” he explained.

Howard agreed with the authors that the “loss of smell may be a marker of generalized aging and should be taken seriously by older people and their doctors.”

However, those with a poor sense of smell shouldn’t necessarily be worried, as the results apply broadly to populations rather than individuals, McConway said. And the results don’t directly relate to those who aren’t between 71 to 82 years old.

“There can be sizable differences between people’s own assessment of how well they can smell and measurement of their sense of smell by an objective test (as was used in this research),” he said.

Earlier this month, a separate study published in the journal Open Heart also looked at another factor linked with the risk of death: resting heart rate.

By studying 798 men living in Sweden, scientists concluded that those with a resting heart rate of 75 beats per minute were twice as likely to die early and develop heart disease.

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