During the peak of the COVID-19 pandemic, loss of sense of smell became a sure-shot sign of the SARS-CoV-2 infection. In some patients, the condition lingered on for weeks and months, while many others reported experiencing a distorted sense of smell, also known as parosmia.
However, it may be surprising to learn that smell loss is not only associated with COVID but can also be an indicator of neurological problems like Alzheimer’s disease, suggests a study published in the journal Neurology.
Also Read: Factors That Can Cause Loss Of Smell Other Than COVID-19
What Is Alzheimer’s Disease?
Alzheimer's disease is a neurological disorder that leads to cognitive decline. According to the World Health Organization (WHO), it is the most common form of dementia, contributing to 60–70% of the condition.
Reportedly, nearly five crore people worldwide have Alzheimers or related dementia. Only one in four people with Alzheimer's disease have been diagnosed.
While Alzheimer's can affect anyone, the risk doubles every 5 years after a person reaches the age of 65. Additionally, people with a family history of Alzheimer's, those who experienced head trauma, and individuals with Down's syndrome are at a greater risk of developing the condition.
Can Alzheimer’s Lead To Loss Of Sense Of Smell?
Speaking with the OnlyMyHealth team, Dr Kapil Agarwal, Senior consultant and HOD-Neurology, Marengo Asia Hospital, Gurugram, says, “Alzheimer's disease is characterised by a progressive loss of memory and cognitive function, but it can also cause a variety of non-cognitive symptoms, such as anosmia or loss of sense of smell.”
Researchers involved in the 2023 study published in the journal Neurology found that people with the APOE ε4 variant, who are at a higher risk of Alzheimer’s disease, were found to have a decrease in their ability to smell odours earlier than those without the variant.
Interestingly, the decline in smelling ability did not worsen faster over time in the APOE ε4 group compared to the others. However, it was observed that both the ability to recognise and name smells and cognitive function declined more rapidly with age in those with the APOE ε4 variant.
Although the connection between Alzheimer's disease and smell loss isn't fully understood yet, experts believe it has something to do with damage in the front part of the brain, says Dr Agarwal. This area comprises the olfactory bulb, which processes the signals we receive from our nose. When this area degenerates due to Alzheimer's, it might disrupt those signals and make it harder to smell things properly.
Also Read: Difficulty In Smelling? Here Are The Causes And Treatment For Anosmia
Alzheimer’s Disease Symptoms
Apart from loss of sense of smell, many other symptoms can help identify Alzheimer's disease. These include:
- Memory loss or difficulty recalling recently learned material, significant dates, or events
- Repetition of queries or statements
- Planning and problem-solving challenges
- Difficulty in managing finances, following recipes, or keeping track of bills
- Confusing place or time
- Losing track of location and method of travel
Conclusion
Loss of sense of smell can be an early sign of Alzheimer’s disease, as per research. While the exact connection is unknown, it may have to do with the degeneration of the anterior part of the brain, says Dr Agarwal.
While there is no cure for the condition, there are medications that can help manage cognitive symptoms and improve quality of life for individuals with Alzheimer's disease. According to the doctor, these medications work by regulating neurotransmitters in the brain and may help delay the progression of symptoms. It is best to consult a healthcare provider to decide your course of treatment.