Mind your nose: A randomized controlled trial of olfactory-based memory training for older people with subjective cognitive decline

Abstract

Introduction: Olfactory-based cognitive training may be of benefit to individuals at risk of dementia given the strong association between olfactory impairment and cognitive decline. The Mind Your Nose (MYN) trial compared an olfactory-based memory training protocol (OMT) to a visually-based memory training protocol (VMT) among older adults with subjective cognitive decline.

Methods: Participants (N = 53; 17 males; M_age = 72.77, standard deviation [SD] = 6.12) were randomly assigned in a 2:1 ratio to daily OMT (n = 36) or VMT (n = 17) intervention for 20 days. Outcomes were evaluated at baseline (T0), post-intervention (T1), and 1-month follow-up (T2) and included standardized measures of global olfaction (Sniffin' Sticks) and cognition (National Institutes of Health Toolbox), as well as performance on the olfactory memory (OM) and the visual memory (VM) tasks, and measures of mood and meta-cognition.

Results: A significant interaction was found between treatment allocation, time, and modality of memory task at T1(β = -37.50, p = 0.008) and T2(β = -28.75, p = 0.041). Post-hoc comparisons revealed improvement in trained tasks; OMT led to improvement on the OM task (T1; g = 0.71, p = 0.036; T2; g = 0.72, p = 0.035), and VMT led to improvement on the VM task (T1; g = 1.22, p = 0.011; T2; g = 1.29, p = 0.006). Improvement on the untrained memory task only occurred in OMT (VM task, T1; g = 0.63, p = 0.071; T2; g = 0.74, p = 0.033). No interaction between treatment allocation and time was observed post intervention or at follow-up for global olfactory ability (T1; β = 0.27, p = 0.871; T2; β = -1.27, p = 0.296).

Discussion: Consistent with previous research, transfer gains from the OMT condition to an untrained VM task suggest that olfaction may contribute to a-modal representations of memory. We argue that memory-based olfactory training offers a new frontier for cognitive interventions among those at risk of dementia.

Highlights: Relatively few cognitive training programs engage the olfactory sense.Olfactory memory training offers a new frontier of cognitive training for older adults.Olfaction may contribute to improved performance on trained and untrained tasks.The functional impact of olfactory training should be further explored.

Keywords: cognitive training, memory training, non‐pharmacological interventions; older adults, olfaction, olfactory disorders, olfactory training, smell, spatial learning, subjective cognitive decline.

FIGURE 1

Flow diagram of participant recruitment, allocation, and analysis.

FIGURE 2

Intervention memory task performance by condition and time point. This plot illustrates the trend of mean scores for each intervention condition over time points and across different memory tasks. OMT = Olfactory Memory Training; VMT = Visual Memory Training; OM Task = Olfactory Memory Task; VM Task = Visual Memory Task; T0 = baseline; T1 = post‐intervention; T2 = follow‐up; g = Hedges g T0‐T1 and T0‐T2, followed by 95% CI. For this outcome, lower scores represent better performance.

FIGURE 3

Changes in memory task performance (0.5 SD). OMT = Olfactory Memory Training; VMT = Visual Memory Training; OM Task = Olfactory Memory Task; VM Task = Visual Memory Task; T0 = baseline; T1 = post‐intervention; T2 = follow‐up. Proportions are based on the total number of participants within each intervention condition.