Smell is one of those senses we can easily take for granted. We notice it when something smells wonderful or not so pleasant, or when we lose it with a cold, but we don’t often stop to think about what is happening in the brain each time we inhale an aroma.
What Does Smell Have to Do With Brain Clearance?
We tend to think of our sense of smell as simply a way to experience the world around us. But emerging research suggests it may also offer clues about brain health.
A recent review in Frontiers in Neuroscience explores an intriguing connection between olfactory function, brain-fluid clearance, sleep, and neurodegeneration.
The glymphatic system helps circulate fluid through the brain and remove metabolic byproducts, with much of this activity occurring during sleep. Separately, the nasal lymphatic pathway is considered an important route for cerebrospinal fluid outflow from the brain. Together, these systems create a possible anatomical connection between the nose and brain clearance.
This anatomical connection becomes especially interesting because changes in smell can occur years before more recognizable symptoms of neurological conditions.
The researchers propose that impaired olfactory function and impaired brain-fluid clearance may, in some cases, be interconnected rather than completely separate phenomena. They call this proposed framework the “olfactory-glymphatic syndrome.”
The review notes that olfactory dysfunction has been reported in up to 90% of people with Parkinson’s disease and approximately 85% of people with Alzheimer’s disease.
There is also a metabolic piece to the story. The authors explore whether metabolic and vascular dysfunction could interfere with nasal lymphatic drainage and, in turn, glymphatic function. This remains a hypothesis, but it raises an intriguing possibility that metabolic health, sleep, smell, and brain clearance may be more interconnected than we have appreciated.
Of course, a change in smell is not specific to neurological disease. Aging, sinus and nasal conditions, head injury, infections, and other factors can affect our sense of smell. That is why the researchers emphasize objective testing rather than relying only on how we perceive our own sense of smell.
Don’t Forget to Smell
There is even growing interest in olfactory training, which involves intentionally and repeatedly smelling different scents. Research is beginning to explore whether this type of practice may support aspects of cognition and olfactory function.
Perhaps one simple place to begin is to pay attention. Smell a warm drink, like coffee or tea, before you drink it. Notice the scent of herbs as you chop them. Walk outside and notice the smells in the air. Open a jar of cinnamon, rosemary, or lavender and pause for a moment.
We often think of mindfulness as something we have to practice deliberately. But our senses are giving us opportunities for awareness all day long. Maybe smelling the world around us is not only a way of experiencing it. It is also an invitation to become more aware of the moment we are in.
Takeaway
Pay attention to your sense of smell, particularly if you notice a persistent or unexplained change. Loss of smell has many possible causes and certainly does not mean someone is developing a neurodegenerative disease, but it may be one more piece of information worth discussing with a healthcare professional.
And perhaps most importantly, continue to prioritize sleep, movement, metabolic health, and vascular health, the everyday foundations that support healthy brain aging.
The nose may be more than a sensory organ. It may offer an accessible window into what is happening deeper within the brain.
Article courtesy: Dr Deanna Minich
Image source: https://whyy.org/