Smell Loss Predicts Mortality Risk Regardless of Dementia Conversion

Area of Science:

• Gerontology
• Neuroscience
• Epidemiology

Background:

• Olfactory dysfunction is increasingly recognized as an early indicator of neurodegenerative diseases.
• Previous studies suggest a link between impaired smell and increased mortality risk, but the role of dementia as a mediator is unclear.

Purpose of the Study:

• To investigate if dementia explains the association between poor olfactory performance and mortality risk over a 10-year period.
• To determine if olfactory loss is an independent predictor of mortality.

Main Methods:

• A prospective cohort study involving 1,774 participants aged 40-90 without dementia at baseline.
• Olfactory function assessed using the Scandinavian Odor-Identification Test (SOIT) and self-reported smell ability.
• Incident dementia and mortality were tracked over a decade.

Main Results:

• A higher SOIT score was significantly associated with lower 10-year mortality risk (HR=0.74).
• This association remained significant after adjusting for demographic, cognitive, and health factors (HR=0.92).
• The link between olfactory function and mortality persisted even when controlling for dementia conversion prior to death.

Conclusions:

• Poor odor identification and self-reported olfactory function are linked to increased mortality.
• Dementia does not fully explain the association between olfactory loss and mortality.
• Olfactory dysfunction may serve as a marker for general health deterioration, independent of dementia.