When a fragrance wafted through the bedrooms of older adults for two hours every night for six months, memories skyrocketed.

Participants in a study by University of California-Irvine neuroscientists reaped a 226 percent increase in cognitive capacity compared to another group that received less exposure to scents. The researchers said the study transforms the long-known tie between smell and memory into a non-invasive technique for strengthening memory and potentially deterring dementia.
The study, whose results were reported in August, involved men and women 60 to 85 years old who don’t have memory impairment. All were given a diffuser and seven cartridges, each containing a single and different natural oil. Some received full-strength cartridges, while others were given the oils in tiny amounts. The cartridges were activated for two hours as participants slept.

Cognitive performance was measured by a word list test commonly used to evaluate memory. Participants also reported sleeping more soundly.

Scientists have long known that the loss of olfactory capacity, or ability to smell, can lead to neurological and psychiatric diseases, including Alzheimer’s and other dementias, Parkinson’s, schizophrenia, and alcoholism. Researchers previously found that exposing people with moderate dementia to up to 40 different odors twice a day boosted their memories and language skills, eased depression, and improved their olfactory capacities.

Having people experience the odors while sleeping eliminates “the need to set aside time for this during waking hours,” said Cynthia Woo, one of the researchers.