Does Olfactory Training Improve Brain Function and Cognition? A Systematic Review

Abstract

Olfactory training (OT), or smell training,consists of repeated exposure to odorants over time with the intended neuroplastic effect of improving or remediating olfactory functioning. Declines in olfaction parallel declines in cognition in various pathological conditions and aging. Research suggests a dynamic neural connection exists between olfaction and cognition. Thus, if OT can improve olfaction, could OT also improve cognition and support brain function? To answer this question, we conducted a systematic review of the literature to determine whether there is evidence that OT translates to improved cognition or altered brain morphology and connectivity that supports cognition. Across three databases (MEDLINE, Scopus, & Embase), 18 articles were identified in this systematic review. Overall, the reviewed studies provided emerging evidence that OT is associated with improved global cognition, and in particular, verbal fluency and verbal learning/memory. OT is also associated with increases in the volume/size of olfactory-related brain regions, including the olfactory bulb and hippocampus, and altered functional connectivity. Interestingly, these positive effects were not limited to patients with smell loss (i.e., hyposmia & anosmia) but normosmic (i.e., normal ability to smell) participants benefitted as well. Implications for practice and research are provided.

Physical Function Trajectories and Mortality in Older Adults With Multisensory Impairment

“…Finally, future studies may examine the effect of sensory training or impairment correction on mortality and functional decline. For example, hearing aids or cochlear implantation and olfactory training may be further investigated in this context …”

Olfactory training improves emotion matching ability in 6–9 years old children — preliminary evidence

“…Indeed behavioral studies provided evidence that OT increases semantic verbal fluency (Oleszkiewicz et al, 2022; Wegener et al, 2018), slows down cognitive decline in older people (Oleszkiewicz et al, 2021), and improves fluid cognitive abilities in children after traumatic brain injury (Pieniak et al, 2023). Although the exact mechanism of these changes remains unraveled, they are hypothesized to result from the neuroplastic effects observed in multiple brain regions (Vance et al, 2023).…”

“…Due to the neuroanatomical and behavioral overlap between olfactory abilities and psychological functions, it has been postulated that OT effectiveness may exceed olfaction (Vance et al, 2023). Indeed behavioral studies provided evidence that OT increases semantic verbal fluency (Oleszkiewicz et al, 2022; Wegener et al, 2018), slows down cognitive decline in older people (Oleszkiewicz et al, 2021), and improves fluid cognitive abilities in children after traumatic brain injury (Pieniak et al, 2023).…”

“…Due to the neuroanatomical and behavioral overlap between olfactory abilities and psychological functions, it has been postulated that OT effectiveness may exceed olfaction (Vance et al, 2023).…”

Enhancing Sleep Quality Through Digital Olfaction: Exploring the Efficacy of Aroma Therapy in Sleep Improvement

“…The olfactory system's close connection with the limbic system, which governs emotion and memory, plays a crucial role in sleep-dependent learning and memory [8]. Moreover, olfactory training shows promise in enhancing brain function and cognitive abilities [9]. Given these findings, the development of safe and effective interventions to improve sleep, such as aroma therapy utilizing digital olfaction technology, emerges as a promising new avenue for enhancing sleep quality.…”