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Updated: Jul 21, 2025
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Human Circadian Phenotyping and Diurnal Performance Testing in the Real World
Published on: April 7, 2020
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Variations of olfactory function with circadian timing and chronotype.
Y Mai1, M C Rosbach1, T Hummel1
1Smell and Taste Clinic, Department of Otorhinolaryngology, Technische Universitat Dresden, Germany.
Rhinology
|July 28, 2023
Summary
Human olfactory function varies daily, peaking in the evening and lowest in the morning. Chronotype and BMI may influence this olfactory-circadian rhythm, impacting smell sensitivity.
Area of Science:
- Neuroscience
- Chronobiology
- Sensory Science
Background:
- Animal studies suggest circadian clock regulation of olfaction.
- Human studies on olfactory circadian variation are limited.
- This study investigates diurnal olfactory changes in healthy adults.
Purpose of the Study:
- To examine diurnal variations in human olfactory function.
- To identify factors modulating olfactory-circadian rhythms.
- To explore the relationship between olfaction, nasal airflow, and chronotype.
Main Methods:
- 56 healthy adults underwent olfactory testing (Sniffin' Sticks) across four daily time points.
- Assessments included nasal patency (PNIF), chronotype, BMI, and subjective ratings.
- Generalized linear mixed models analyzed predictors of olfactory threshold.
Main Results:
- Olfactory threshold (OT) and nasal patency (PNIF) showed significant diurnal variation, lowest in the morning and highest in the evening.
- No significant correlation was found between OT and PNIF diurnal changes.
- Morning testing time, evening chronotype, BMI, and nasal patency predicted olfactory threshold.
Conclusions:
- Human olfactory sensitivity exhibits a diurnal pattern, with peak sensitivity in the evening.
- Nasal patency follows a similar diurnal pattern but may not directly drive olfactory changes.
- Chronotype and BMI appear to modulate olfactory-circadian variations, offering insights for diagnosis and treatment.
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