Older People More Prone to Olfactory Habituation After Extended Exposure to Odors

by Linda Kossoff •

CLINICAL QUESTION

What is the impact of subclinical olfactory impairment on odor habituation, where age is used as a proxy?

BOTTOM LINE

Older people experience more notable habituation after extended exposure to odors, most likely due to compromised olfactory function in age.

BACKGROUND: Prolonged or repeated exposure to an odor can temporarily decrease olfactory sensitivity. The mechanism underlying this can be categorized into adaptation, a neuronal-level stimulus adjustment; or habituation, referring to a decrease in the perceptual or behavior intensity. The impact of olfactory dysfunction on lateralized adaptation and habituation remains ambiguous.

STUDY DESIGN: Prospective study

SETTING: Department of Otorhinolaryngology, Smell and Taste Clinic, TU Dresden, Dresden, Germany

SYNOPSIS: Researchers enrolled 80 normosmic individuals (74% female; mean age 44.6 years)—a younger group (n = 40; mean age 27.7 years) and an older group (n = 40; mean age 61.5 years)—in this study. Prior to experiments, the individual olfactory threshold for the rose-like odorant phenylethyl alcohol (PEA) was assessed separately for the left and right nostrils. At baseline and over the entire cohort, the mean olfactory threshold score for the exposed and non-exposed sides did not differ significantly. In experiment number one, a nasal clip continuously delivered PEA odor to one nostril for 10 minutes. In experiment number two, the exposure duration was expanded to two hours. Threshold, intensity, and pleasantness were reassessed immediately after clip removal. For the entire group, results showed a notable decline in T score on both the ipsilateral and contralateral sides after just 10 minutes of exposure, with habituation even more pronounced after two hours.  This effect could be observed bilaterally, although it was more distinct on the exposed side. Older participants showed a more pronounced ipsilateral habituation after two hours compared to the younger group. Study limitations included a potential for direct habituation on the contralateral side.

CITATION: Hintschich CA, Ma C, Hähner A, et al. Pronounced olfactory habituation with age. Laryngoscope. 2024;134:3765-3768.