Can Poor Sense of Smell in Older Adults Lead to Chronic Diseases?

June 28, 2022

Over the past two and a half years of the COVID-19 pandemic, some people have begun thinking about their sense of smell. Honglei Chen has been thinking about it for more than a decade.

That is because much of his research focuses on whether a poor sense of smell in older adults can herald the development of some chronic diseases. Previous research, including by Chen, from the MSU College of Human Medicine, has established a link between a decline in the sense of smell – or poor olfaction – and the development of Parkinson’s disease and dementia.

The National Institute on Aging recently awarded Chen, MD, PhD, a Michigan State University Foundation Professor of Epidemiology and Biostatistics, a $2.7 million grant to study what other adverse health outcomes might be foreshadowed by a poor sense of smell.

“While the connections to Parkinson’s and dementia are well established, our recent findings suggest poor olfaction has much more to tell about the health of older adults,” Chen said. “The goal of this grant is to see what other diseases poor olfaction potentially heralds.”

The nose, he said, is “the interface between the environment and the human body,” suggesting that, while a person might have a genetic predisposition to certain diseases, exposure to substances in the environment could trigger those diseases. Your nose may be among the first to warn you.

Beyond Parkinson’s and dementia, his study will look for possible links to pneumonia, and other lung diseases, cardiovascular disease, diabetes, functional decline, frailty, and markers of age acceleration.

Up to 25 percent of adults over age 65 experience a loss of smell. Some diseases, including Parkinson’s and dementia, often begin years or decades before they can be clinically diagnosed, making an early warning even more important.

“Poor olfaction is so common in older adults, but most people affected do not know they have it. If it is meant to send you an early warning, you better know about it,” Chen said. “As we know more about the potential implications of poor olfaction on the health of older adults, we may take actions to promote healthy aging.” That could include lifestyle changes, such as in diet and exercise.

The loss of smell associated with COVID usually is temporary, and it is too new to learn whether it could forewarn of other diseases later in life. But in general, the possible link between poor olfaction and other diseases does not get nearly enough attention, Chen said.

 “This line of research excites me, and I would love to see more research in this direction,” he said.