COVID-19 has brought a lot of recent attention to smell loss. Loss of smell can be one of the first or only signs of COVID-19, but there are also many other medical conditions for which sense of smell can raise suspicion.
One big area of interest is a group of diseases known as “neuro-degenerative diseases”. These are diseases that can cause slowly worsening function of the brain, spinal cord, and nerves. Some common examples of these are Alzheimer’s disease and Parkinson’s disease. It is very common for patients with these diseases to have decreased or no ability to smell. What causes these patients to lose their smell is not clear, but it can be due to the nerves of smell themselves being affected, or maybe it is because patients are no longer able to recognize certain smells. Whatever the cause, we know that smell loss symptoms can often start many years before any other symptoms of Alzheimer’s or Parkinson’s disease.
However, other diseases are also linked to smell loss. Patients with smell loss can have higher rates of depression, anxiety, and death. It is not clear how losing our smell affects our health and wellness, but many different theories are being studied. These theories include ideas that suggest loss of smell can cause a decreased appetite and poor diet, or losing enjoyment in normal activities and feeling isolated, and also increasing one’s risk of being exposed to dangerous things in our environment. While these theories are all interesting, none have yet been proven, and we have no great way of predicting which patients who lose their smell will go on to develop other problems.
If there is a silver-lining to COVID-19 smell loss, it is that it has raised attention to smell loss in general, and to all of the other diseases and conditions that smell loss is linked to. Research efforts are underway world-wide to tackle and treat smell loss, which hopefully will be mean that in the next few years we will have better understanding of how smell impacts our health and have tools available for patients who suffer from smell disorders.