Poor sense of smell linked to nearly 50% higher risk for death
Older adults with a poor sense of smell demonstrated a 46% greater risk for dying that was partially explained by dementia, Parkinson’s disease and weight loss, according to findings published in Annals of Internal Medicine.
“Poor olfaction is common among older adults and has been linked to higher mortality,” Honglei Chen, MD, PhD, professor of epidemiology and biostatistics at the Michigan State University College of Human Medicine, and colleagues wrote. “However, most studies have had a relatively short follow-up and have not explored potential explanations.”
Liu and colleagues conducted a community-based prospective cohort study to determine how poor olfaction affects mortality in older adults and to examine possible reasons for the relationship. The researchers administered the Brief Smell Identification Test to 2,289 adults aged 71 to 82 years (37.7% black; 51.9% women) in 1999 and 2000 to identify olfactory impairment. The smell test asked participants to identify 12 common odors. For each correct answer, participants were given one point. Participants were categorized as having good, moderate or poor sense of smell based on their smell test scores.
At 3, 5, 10 and 13 years, the researchers assessed all-cause and cause-specific mortality.
By year 13, a total of 1,211 participants died.
The cumulative risk for death was 46% higher at year 10 (RR = 1.46; 95% CI, 1.27-1.67) and 30% higher at year 13 (RR = 1.3; 95% CI, 1.18-1.42) among participants with poor olfaction, compared with those with good olfaction. These results were seen in both men and women and whites and blacks.
The association between mortality and poor olfaction could not be explained by confounders, including demographic characteristics, lifestyle and comorbid conditions.
The association was seen in participants with excellent to good health at baseline (10-year mortality RR = 1.62; 95% CI, 1.37-1.9), but not those with fair to poor health (10-year mortality RR = 1.06; 95% CI, 0.82-1.37).
Participants with poor olfaction had a greater risk for mortality from neurodegenerative and cardiovascular diseases. The researchers found that 22% and 6% of the higher 10-year mortality were explained by neurodegenerative diseases and weight loss, respectively, among participants with poor olfaction.
“What the clinical implications of these findings are is the ultimate question we need to answer,” Chen told Healio Primary Care Today.
“This study provides initial clues,” he said. “Poor sense of smell may have broader clinical implications beyond what we have already know about its role in dementia, Parkinson’s or poor nutrition, and we need to identify and define the rest. It may be a sensitive marker for deteriorating health in older adults before it can be otherwise recognized. What that means, we do not yet know.”
More research is needed to understand the exact clinical implications of poor olfaction before PCPs begin to screen for or ask questions about sense of smell, according to Chen. – by Alaina Tedesco
Disclosures: Chen reports no relevant financial disclosures. Please see study for all other authors’ relevant financial disclosures.