Olfactory Deficits Signal Mortality Risk From Neurodegenerative Causes in Older Adults
Each additional incorrect answer by older adults on an odor identification test increased all-cause mortality risk by 6% over 6 years, according to study results published in JAMA Otolaryngology-Head & Neck Surgery.
Researchers investigated links between olfactory deficits and all-cause and cause-specific mortality in 2524 older adults. Participants, who were residents of Kungsholmen, Stockholm, Sweden, and an average of 71.9 years of age, had their olfactory ability tested using the 16-item Sniffin’ Sticks Odor Identification task. Mortality was assessed over 12 years of follow-up using the Swedish National Cause of Death register.
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At 6 years, 17.6% of participants had died; at 12 years, 38.4% had died.
“In multiadjusted models, each incorrect answer on the odor identification test was associated with an approximately 6% increased mortality risk at 6 years and with a 5% increased risk at 12 years …” reported corresponding author Ingrid Ekström, PhD, of Karolinska Institutet and Stockholm University, Stockholm, Sweden, and coauthors. “A score of 6 items less would correspond to a 42% increased risk of all-cause mortality at 6 years and a 34% increased risk at 12 years.”
Cause-specific mortality models showed the olfaction-mortality association was highest for neurodegenerative causes of death, according to the study. Estimated associations were smaller but still notable for respiratory and cardiovascular mortality.
At 6 years, meaningful mediators of the olfaction-mortality association were incident dementia, which accounted for 23% of the total association; frailty, 11%; and malnutrition, 5%.
“Together, these mediators explained 39% of the olfaction-mortality association at 6 years,” researchers wrote.
At 12 years, frailty remained a mediator, accounting for 9% of the olfaction-mortality association, the study found.
“Our results further underscore the evolving influence of frailty and neurodegeneration on the olfaction-mortality relationship,” researchers wrote. “Overall, our findings reinforce olfactory deficits as a marker, rather than a direct contributor, to health outcomes linked to increased mortality.”
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