Smell and Dementia

The sense of smell is accomplished through our olfactory system, which is an old system in our biological development. It is also one of the most evocative.

Smell acts as a portal to our emotions. It transports us directly to another time, another place and the only other medium that does this so quickly is the auditory sense--through music. But unlike music-- which can be written down and transferred in what Karl Popper calls World 3--smell is ephemeral.

Smell is somewhat undefined. Good, bad, sweet, acrid, then we loose track of translating the subtle smells into language. Smell has its own language and it cannot comfortably be translated into words.

Smell has power, it is evocative and nuanced so that a particular smell can immediately transport us to our first kiss, or the fear of high school, or your first child being born. Visceral and strong emotions which are hidden in the recesses of your mind. Never lost but subdued until dementia starts to erase them.

The olfactory system has a direct path to the brain. With humans, this system starts with the nose and ends a short distance away at the base of our brain. Olfactory receptors, with very thin fibers,  run  from the roof of the nasal cavity through perforations in the skull ending in the olfactory bulbs, which are a pair of swellings underneath the frontal lobes. It is the only sense that has such a direct physical connection to the brain. It is is also the first to be affected with the onset of dementia or Alzheimer’s. When the brain is affected by dementia, the area that deteriorates first is the area that is responsible for smell.

There is currently a patent, by researchers from Columbia University lead by Davangere Devanand, for a test using scents that include cheese, clove, fruit punch, leather, lemon, lilac, lime, menthol, orange, pineapple, smoke and strawberry. Using this test, the clinicians can predict that an individual who cannot recognize three of the ten scents are five times more likely to develop Alzheimer’s. It has also been found to predict Parkinson’s disease as well as certain types of schizophrenia and brain tumors.

Many people who lose their sense of smell also complain that they lose their sense of taste. Smell enhances the information we get from the mouth; salty, sweet, sour, and bitter tastes. Loss of taste might explain why weight loss is also an indication of dementia. It is not the weight loss on its own, but rather the loss of smell, which brings about the loss of appetite and consequently to diminished appetite.

There are some sixty seven medical conditions identified as possibly causing loss of smell--dementia being one of them. Some of these causes are temporary, such as colds, and nasal allergies such as hay fever.  It may also occur due to some medications and localized nasal polyps and tumors. Such factors reduces the odds of making the patent smell test a very reliable indicator in predicting dementia. But for individuals, it is important to notice changes in how well we can smell. So if you are having trouble with smell, check with your physician first to make sure that this is not a temporary condition.

Mario Garrett, Ph.D., is a professor of gerontology at San Diego State University and can be reached at mariusgarrett@yahoo.com