Effectiveness of olfactory stimulation on improving cognitive function and behavioral and psychological symptoms of dementia in older adults with mild cognitive impairment or dementia: a systematic review and meta-analysis.

OBJECTIVES

This systematic review and meta-analysis examined the effectiveness of olfactory stimulation on cognitive function and behavioral and psychological symptoms of dementia (BPSD) in older adults with mild cognitive impairment (MCI) or dementia.

METHOD: Following PRISMA 2020 guidelines PROSPERO (CRD42025641764), five databases were searched up to July 2025 for randomized controlled and quasi-experimental studies. Risk of bias was assessed using RoB 2.0 and ROBINS-I. Meta-analyses were conducted using Comprehensive Meta-Analysis software. Subgroup analyses examined differential effects in MCI and dementia populations.

RESULTS

Ten studies met inclusion criteria, and six were included in meta-analyses. Olfactory stimulation showed a small, non-significant effect on cognitive function (Hedges' g = 0.25, p = 0.14). Subgroup analysis revealed a moderate, marginally non-significant effect in MCI (Hedges' g = 0.75, p = 0.08) and a small, non-significant effect in dementia (Hedges' g = 0.16, p = 0.39). Olfactory stimulation was significantly associated with improvements in agitation symptoms (Hedges' g = 0.73, p < 0.001) and depression (Hedges' g = 1.81, p < 0.001) among individuals with dementia.

CONCLUSION

Olfactory stimulation may not significantly enhance cognition but suggests potential benefit in reducing neuropsychiatric symptoms among individuals with dementia, supporting its role as a non-invasive, feasible, low-cost non-pharmacological intervention.