Can loss of smell predict risk?

People begin to lose their sense of smell as they age and previous research shows olfactory dysfunction begins to increase once we hit age 60.

“Smell loss or impairment affects about a quarter of older adults,” Honglei Chen, PhD, MSU Research Foundation Professor in the Department of Epidemiology and Biostatistics at Michigan State University College of Human Medicine, and lead author of this study, told Medical News Today.

“The public awareness is low though — only about 30% of those with smell loss know they have it,” he noted.

“We learned in the past two decades that smell loss is one of the most important early markers of dementia and Parkinson’s disease,” Chen continued. “Interestingly, emerging data, including ours, suggests that smell loss may have more profound implications on the health of older adults, including [the] risk of death, pneumonia, functional decline, and frailty.”

Smell loss may also be related to cardiovascular health, added Keran Chamberlin, a doctoral researcher in epidemiology at Michigan State University, and first author of this study.

“For example, preliminary data found that subclinical cardiovascular changes may affect the sense of smell of older adults,” Chamberlin explained to MNT.

“On the other hand, we may speculate that smell loss may adversely affect one’s nutritional intake, mood, and daily activities, which may jeopardize cardiovascular health over time. This may be especially relevant to heart failure.”

– Keran Chamberlin

“As heart failure is an advanced multi-faceted syndrome, its progression may be exacerbated by the elevated vulnerability,” she added. “Therefore, smell loss may be related to cardiovascular health as a marker, contributor, or both.”

For this study, researchers analyzed data from about 2,500 people in the National Institute on Aging’s Health ABC Study. Participants who first enrolled in this study in 1997 and 1998 were healthy older adults between the ages of 70 and 79.

Study participants were followed starting from the time their sense of smell was tested at a clinic visit in 1999 or 2000 for up to 12 years or until they had a cardiovascular event or passed away.

Scientists were analyzing the data to see if they could find a link between loss of smell and cardiovascular conditions including heart attack, stroke, congestive heart failure, angina, or death caused by coronary heart disease.

At the study’s conclusion, researchers found participants with olfactory loss had about a 30% increased risk of developing congestive heart failure compared to those who did not lose their sense of smell.

“Given what we have discussed about the possible connections between smell loss and cardiovascular health, we are not totally surprised by our finding,” Chen told MNT.

The study authors also reported finding no link between olfactory loss and heart disease or stroke.

“We are a bit surprised by the fact that we only identified this association for heart failure, but not for coronary heart disease or stroke,” Chamberlin said.

“Admittedly, we do not have a good explanation for this. However, compared to coronary heart disease or stroke, congestive heart failure is a more complex and advanced syndrome with structural or functional cardiac abnormality,” she told us.

“Besides atherosclerosis, other myocardial stressors can also trigger heart failure hospitalization,” she added. “Smell loss may signify higher vulnerability to myocardial stressors beyond atherosclerosis. Nevertheless, our findings are preliminary, waiting for confirmation.”

Should readers worry about potential cardiovascular concerns if they find their sense of smell is changing? Chen said that at this stage, the general public should understand that the findings are preliminary.

“We need to further evaluate the potential role of smell function as a marker for heart failure, as well as for stroke and coronary heart diseases,” he continued.

“Hopefully, this study will lead to a series of investigations on smell and cardiovascular health and provide the public [with] informed strategies to maintain cardiovascular health,” said Chen.

“Our next step is to further investigate this topic in more diverse populations,” Chamberlin added. “If the findings are confirmed, by us and by others, we should investigate the underlying mechanisms that link smell loss to cardiovascular health.”

After reviewing this study, Cheng-Han Chen, MD, a board-certified interventional cardiologist and medical director of the Structural Heart Program at MemorialCare Saddleback Medical Center in Laguna Hills, CA, not involved in the research, told MNT he found the results surprising as the sense of smell is not typically something we normally associate with heart function.

“Based on our understanding of heart failure and heart function, it is not clear why there would be a link to our sense of smell,” the cardiologist continued.

“This association found in the research may simply be due to an aging body developing both conditions concurrently. Future research in this area should focus on validating a relationship between the sense of smell and heart failure with larger studies preferably with longitudinal assessment of olfaction. In addition, the potential underlying mechanisms for such a relationship should be studied,” he advised.

“As heart failure is a major source of morbidity and mortality in our population, identifying factors that predict heart failure will better enable us to screen, intervene, and potentially prevent new heart failure in patients,” the cardiologist added.

MNT also spoke with Richard Wright, MD, a board-certified cardiologist at Providence Saint John’s Health Center in Santa Monica, CA about this study. Wright was also not involved in the research.

He told us he found the prognostic potential of impaired sense of smell intriguing, provocative, and important.

“Any simple criterion to predict the eventual development of heart failure would be clinically welcome,” Wright said.

“However, like many good studies, the current analysis raises more questions than it answers. As a failing sense of smell is strongly associated with aging, as is the syndrome of congestive heart failure, the most straightforward interpretation of these results is that some individuals age at a more rapid rate than others. Such people might lose their sense of smell and cardiac function at a more rapid rate than others, and hence the observed correlation of these two clinical conditions may simply be due to differential rates of aging — analogous to the various ages at which gray hair appears.”

– Richard Wright, MD

“This observed correlation needs further investigation using clinical data — rather than billing and encounter information — correlating the type of heart failure, chronic medications used, and more expansive exploration of co-morbidities and social determinants of health to truly understand whether heart failure ‘causes,’ or is just correlated with olfactory dysfunction,” he added.