Is there a connection between cognitive performance and the sensitivity of our nose?

The humble hooter is not a part of our anatomy that usually enjoys particular attention, or even exercise, but some striking research has recently linked our noses’ sensitivity to our cognitive performance. One neurobiologist working at a university in the US even confidently claims that by middle-age, all-cause mortality can be predicted by olfactory ability. The mechanism of smell is where molecules entering the nose are dissolved in mucus. These molecules then bind to tissue in the nasal cavity that is packed with olfactory receptor neurons. Signals are then sent to the olfactory bulb in the brain for identification.

Olfactory dysfunction is now being associated with a host of conditions such as cardiovascular disease, polycystic ovary syndrome and arthritis, along with a plethora of neurological conditions such as dementia and Parkinson’s. Furthermore, a major study in Germany involving some 7,000 participants revealed a clear correlation between olfactory capacity and cognitive test results, with poorer memory and learning, verbal fluency and attention being noted among the lowest scorers. Similar conclusions have been reached with other studies. And quite remarkably,  people’s odour sensitivity and performance appeared to be a better predictor of the progression of Alzheimer’s than the current assessment model widely used to identify dementia risk. One of the reasons why lost smell sensitivity is thought to be associated with brain deterioration is because of the wiring of the brain. Senses such as vision, touch and hearing are first registered in the brain at a “turntable” called the thalamus, which processes the information before distributing it across the brain. But smells go straight to the olfactory bulb in the forebrain with its direct links to other areas of the cortex involved with functions such as emotional processing and learning. This makes the olfactory system a superhighway to the memory and emotional functions of the brain, so to speak.

Smell registration is also believed to keep our immune system up to scratch. After being exposed to unpleasant odours (so potential pathogens) the immune system is provoked, with higher levels of inflammatory molecules recorded in saliva in preparation of a potential assault.  And bad odours are usually harbingers of bad things so best kept away from - smelling our surroundings can help us to avoid environments that trigger inflammation.

All this has now given rise to so-called smell-training programmes, being commercially available kits requiring users to sniff various aromatic compounds such as eucalyptus or clove for a few minutes a day over a few weeks or months. Trials have shown promising evidence that smell training can really slow or even reverse certain forms of cognitive decline with its brain boost. So maybe it would be a wise move to devote a little more attention to our own personal sense of whiff.