Soon after graduating from medical school, I stopped checking the sense of smell in my neurologic exam, just like most of my colleagues. It’s inconvenient to carry different smelly objects around on the hospital ward or in the clinic. So, “Cranial Nerves I-XII normal” turned into “Cranial Nerves II-XII normal”. There was a brief period during the Covid epidemic where we at least asked about our patients sense of smell.
Researchers at Sweden’s Karolinska institute did a 12 year longitudinal study of the sense of smell and the mortality data of more than 2500 participants with an initial average age of 72. The researchers used a 16 item odor identification test and classified the participants into three groups: Anosmic (0-6 correct answers), Hyposmic (7-10 correct answers) and Normosmic (11-16 correct answers).
At both their 6 and 12 year follow-ups the anosmic group had almost 70% higher relative risk of mortality than the normosmic group. For each wrong answer, the mortality increased 5-6%.
Interestingly, the only causes of mortality involved were neurodegenerative deaths (mostly Alzheimer’s disease), respiratory and cardiovascular diseases. There was no association with cancer mortality.
So, maybe it’s time to reintroduce the first item in the neuro exam we all learned in school...