Losing sense of smell could indicate impending death

Henrietta Brewer
May 3, 2019

"I would not be surprised if someday the sense of smell was included as a simple checkup, to see if this important human sense is affected", said senior researcher Dr. Honglei Chen, a professor of epidemiology and biostatistics at Michigan State University.

Writing in the Annals of Internal Medicine, researchers in the USA and Sweden report how more than 2,200 people aged between 71 and 82 undertook smell identification tests near the turn of the millennium, which were then followed up over 13 years. In this test, they were asked to identify 12 common smells, and they remained in the study until their deaths or until 2014, whichever came first.

People who started out the study in excellent or good health were 62 percent more likely to die by year 10 when they had a poor sense of smell than when they had a keen nose, researchers report in the Annals of Internal Medicine.

People who eat poorly due to their lost sense of smell might also be at higher risk of developing heart disease, due to malnutrition or by eating unhealthy junk foods that have a vivid taste, Chen added. Those with poor sense of smell has a 46 percent risk of dying in the next decade and 30 percent risk of mortality within 13 years. Approximately 2,300 individuals between ages 71 and 82 were followed over a 13-year period.

Poor sense of smell is known as an early sign for Parkinson's disease and dementia and is associated with weight loss.

It tells us that, in older adults, impaired sense of smell has broader implications.

"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". 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.

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

"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.

"This raises the interesting possibility that loss of smell may be a marker of generalized aging and should be taken seriously by older people and their doctors.' Professor Kevin McConway, an expert in applied statistics at the Open University, said the findings were 'a real advance".

Poor sense of smell may be an early warning for poor health in older age that goes beyond neurodegenerative diseases that are often signal the beginning of physical or mental decline, the results also suggest. "We need to find out what happened to these individuals", says Chen, who plans to investigate potential reasons in further studies. What's more, the apparent link between the sense and mortality could be down to factors that affect both but were overlooked.

Other reports by iNewsToday