An impaired sense of smell can stem from numerous things, including sinus infections, smoking, medications, head injuries, aging and more. Might deterioration of the olfactory sense also be a sign of declining cognitive abilities?

THIS STUDY involved 1,430 adults who averaged 80 years old and had no cognitive deficits at the start of the study. Standardized testing of people’s sense of smell was done periodically over 3 1/2 years. In that time, 250 participants were diagnosed with mild cognitive impairment, mostly memory problems. The condition of 64 of those with the most serious cognitive issues progressed to dementia, including Alzheimer’s disease. Overall, as people’s problems with smell increased, so did their risk for cognitive decline. Those whose sense of smell declined the most were more than twice as likely to develop memory issues as those experiencing the least decline. Among people with the most advanced cognitive decline, those with the worst scores on the smell test were about five times as likely to have progressed to dementia as were those with the least loss of smell capability.

WHO MAY BE AFFECTED? Older people, who face an increased risk for both diminished sense of smell and of cognitive function, including loss of memory. However, not all memory problems equate to a cognitive impairment diagnosis, nor is hearing loss automatically attributed to growing old. People with these issues should consult their doctor.

CAVEATS People with Parkinson’s disease or alcoholism were excluded from the study as these conditions can affect the sense of smell, but the researchers did not screen out people with other conditions — including allergies, nasal diseases and head trauma — that also can affect olfactory ability.

FIND THIS STUDY Nov. 16 online issue of JAMA Neurology (www.jamaneurology.com; click on “Online First”).

LEARN MORE ABOUT the sense of smell at nidcd.nih.gov (use A-Z Index) and www.entnet.org (search for “smell & taste”).

The research described in Quick Study comes from credible, peer-reviewed journals.