Of all the senses we love to indulge, scent is often neglected – but the right smells could be just what your brain needs to keep it whirring in old age.

Researchers at the University of California, Irvine have uncovered strong evidence that enriching the air with fragrances improves cognitive performance by strengthening a critical connection between neurological areas involving memory and decision-making.

Their experiment, involving 43 men and women aged 60 to 85, suggests cognitive decline and conditions such as dementia might be slowed by simply diffusing a different choice of perfumes through the bedroom before bed each night.

Keeping the old gray matter stimulated as we age is vital to maintaining good cognitive health. That doesn't just mean keeping up with the daily crossword – it means peppering our environment with all kinds of sights and sounds for the brain to chew on.

For other animals, enriching the environment with odors has been shown to stimulate neuroplasticity, especially in tests involving animals with human-like symptoms to neurological disorders.

It's not exactly a stretch to believe humans could also benefit from experiencing a complex 'scent-scape'. Physiologically speaking, our ability to detect smells deteriorates before our cognitive ability begins to decline.

Losing this sense also correlates with a loss in brain cells, hinting at a strong connection between smell and neurological function.

"The olfactory sense has the special privilege of being directly connected to the brain's memory circuits," said neurobiologist Michael Yassa when the results were revealed in August.

"All the other senses are routed first through the thalamus. Everyone has experienced how powerful aromas are in evoking recollections, even from very long ago. However, unlike with vision changes that we treat with glasses and hearing aids for hearing impairment, there has been no intervention for the loss of smell."

To determine whether cognitive decline can be saved with this kind of sensory stimulation, Yassa and his colleagues provided 20 of the study's recruits with an assortment of natural oils containing fragrances of rose, orange, eucalyptus, lemon, peppermint, rosemary, and lavender.

Oil added to a heater
Aromatic oils could help work the brain by enriching the environment with smells. (Microgen Images/Science Photo Library/Getty Images)

The rest of the group were provided with a 'sham' that contained trace amounts of an odorant. All of the participants were required to use one of the oils with a diffuser to perfume their home for two hours every night over a six-month period, rotating through their menu of fragrances.

A battery of neuropsychological tests was then used to compare the volunteers' memory, verbal learning, planning, and attention-switching skills before and after the six-month trial.

Astonishingly, there was a clear 226 percent difference between the responses provided by those who were exposed to a variety of fragrances and individuals in the control group. A scan of their brains also revealed a significant change in the anatomy linking areas of the brain critical in memory and thinking within the test group.

As all of the volunteers were of similarly sound mental health, the researchers aim to now see if the results continue to hold for people already diagnosed with a degree of cognitive loss.

No matter what age or state of mind, giving your nose something to do when the lights go out and the silence sets in isn't exactly an unpleasant way to exercise the mind at night.

This research was published in Frontiers in Neuroscience.

An earlier version of this article was published in August 2023.