Smell has unusually direct connections with brain regions involved in memory and emotion. Researchers have therefore asked whether regular olfactory enrichment might affect cognition in older adults.
A small study reported a striking difference on one memory test after participants were exposed to changing scents while they slept. The result is interesting, but the percentage attached to it is easy to misunderstand.
This article is for general information and does not provide medical or mental-health advice.
What the experiment did
The study included 43 healthy older adults. Participants in the enrichment group used an odorant diffuser for two hours each night over six months, rotating among seven scents. The control group received much lower concentrations.
The enriched group performed better than controls on one verbal-memory measure. Researchers also reported a difference in a white-matter pathway connected with memory.
How to read the 226 percent figure
The 226 percent number describes the reported gap between two small groups on one test after the intervention. It does not mean that each participant improved their memory by 226 percent, and it does not establish protection against dementia.
Small samples can produce unstable estimates, and the study tested multiple outcomes. Replication in larger and more varied groups is needed before nighttime scent exposure can be treated as a reliable cognitive intervention.
Editor’s note: This article was substantially revised on September 14, 2026, to explain the sample size and the meaning of the widely quoted percentage.
