Can Loss of Smell Predict Heart Failure?

Loss of the ability to smell normally, a common sensory impairment with age, may help predict or even contribute to the development of heart failure, a new study suggests.

The study, published in the Journal of the American Heart Association, adds to a growing body of evidence about the role that poor sense of smell may play in the health of older adults.

"We know that it is a marker for neurodegenerative diseases such as Parkinson's disease and dementia," said Dr. Honglei Chen, lead author of the study and a professor in the Department of Epidemiology and Biostatistics at Michigan State University College of Medicine in East Lansing.

"We are finding that the sense of smell may be important to the health of older people, and this has prompted us to explore how it may be linked to diseases other than neurodegeneration."

With age, it is not uncommon to lose the ability to smell. Research shows that nearly one in four people experience a decline in their sense of smell by the age of 50. After age 80, more than half of people experience this. Losing the ability to smell normally can lead to decreased quality of life, including loss of enjoyment of food and increased health risks due to problems such as decreased ability to detect spoiled food or gas leaks.

Loss of smell can have other consequences. Previous research has shown that poor sense of smell may be an early marker of cognitive loss, linking olfactory dysfunction to poorer overall cognitive performance, memory and language.

Olfactory dysfunction has also been identified as a strong predictor of death within 10 years in older adults and may be a potential sign of slow cell turnover or years of exposure to toxic environmental factors—or both.

With dementia and Parkinson's disease accounting for just 22% of the excess mortality associated with poor smell, researchers in a new study asked whether olfactory dysfunction could be a marker of broader health problems.

Chen and colleagues analyzed data on 2,537 people from the National Institute on Aging's Health ABC Study, which examines the relationships among conditions associated with aging, social and behavioral factors, and functional changes in older adults. When participants were enrolled in the study in 1997 and 1998, they were high-functioning adults aged 70 to 79 years living in the Pittsburgh and Memphis, Tennessee, areas.

Participants were followed from the time their sense of smell was tested at their three-year clinic visit in 1999 or 2000 until age 12 or until the time of the cardiovascular event or death.

Researchers looked for a link between poor sense of smell and heart attack, stroke, angina, death from coronary heart disease, or heart failure, which occurs when the heart doesn't pump blood as well as it should. Researchers considered a person to have heart failure if they were hospitalized overnight with the condition.

Smell was tested by asking participants to smell and identify 12 items from a list of four possible responses. One point was given for each correct answer, for a total of 0 to 12. Poor sense of smell was defined as a score of 8 or less. In previous analyzes of the same group of participants, the researchers found strong associations between poor sense of smell and Parkinson's disease, dementia, mortality, and hospitalization for pneumonia.

In the new analysis, participants with loss of smell had about a 30% higher risk of developing chronic heart failure compared with participants with a good sense of smell. There was no link between loss of smell and heart disease or stroke.

Chen said it is not yet clear whether a poor sense of smell contributes to the development of heart failure or simply predicts it.

"Poor sense of smell may be associated with accelerated aging," he said, adding that this is an area that requires more study.

This area of research is in its early stages and raises many interesting questions, said Dr. Khadija Brisette, a heart transplant cardiologist with the Advanced Heart Failure, Mechanical Circulatory Support and Cardiac Transplantation Team at Indiana University Health in Indianapolis.

"I'm wondering whether the loss of smell is a biomarker of another physiological process," said Brisette, who was not involved in the study. "It's not entirely clear how loss of smell can lead to heart failure."

Of the many causes of heart failure, heart disease is the leading one, said Brisette, also a professor of medicine at Indiana University. "Loss of smell was not associated with coronary artery disease in this study, which makes me think even more about this connection."

Brisette also wondered if there was anything we could learn from people who have lost their sense of smell due to COVID-19. This symptom may persist for weeks or longer in some people. The study analyzed data collected before the COVID-19 pandemic.

"This study does not show cause and effect," she said. "It raises questions, but that's good because it can help us find new targets for improving care."