The cause of Alzheimer’s disease still remains a mystery among researchers. Alzheimer’s is the most common form of dementia, and the National Institute on Aging estimates more than 6 million people have this disease. Some of the main features of Alzheimer’s are plaques and tangles that develop in the brain and a loss of connection among neurons. While Alzheimer’s and other types of dementia often result in memory problems, researchers are looking into how your olfactory system (your sense of smell) is connected to your brain health.
In a 2023 study in Frontiers in Immunology, researchers found that regularly inhaling menthol boosted the immune system and memory in healthy mice. Menthol also prevented further cognitive decline in the mice modeled for Alzheimer’s. The researchers believe that menthol helps to stimulate the immune system while blocking an inflammatory molecule called interleukin-1-beta (IL-1β) that is linked to cognitive decline. The study suggests that the sense of smell might regulate your immune system and brain function.
How specific scents might improve memory
Before you take a whiff of Altoids to prevent Alzheimer’s, however, it’s a little more complicated. The study showed how important the olfactory system is for brain health. When the researchers blocked the mice’s sense of smell, their immune system weakened and their memory declined. The study also found how important the immune system is for brain health. The researchers removed particular cells that regulate the immune response. This lowered the pro-inflammatory cytokine IL-1β and led to improvements in memory.
However, not all scents affect the immune system and memory in the same way. According to a 2018 article in Frontiers in Immunology, carvone, which can smell like caraway or spearmint, improved the memory and immune system of one type of mice and compromised the immunity and memory in others. It’s important to note that both of these studies were conducted on mice, so more research is needed on humans.
When you notice a particular smell, receptors in your nose send signals to your brain. This part of your brain is along the same brain circuitry as your memory. A 2021 study in the Journal of Clinical and Experimental Neuropsychology found that certain scents can help people recall more vivid details in memory compared to photos or sounds, even in people with Alzheimer’s.
Losing sight, hearing, smell as early dementia symptoms
A common symptom in the first wave of the COVID-19 pandemic was losing your sense of smell. However, this could also be an early symptom of Alzheimer’s or other neurodegenerative diseases such as Parkinson’s, according to the National Institute on Aging. People who have problems differentiating a variety of scents could have biomarkers of Alzheimer’s even before they experience problems with cognitive impairment.
Older adults should monitor their hearing and vision health regularly because changes in these senses could be linked to cognitive decline. Although some vision problems such as cataracts can occur with age, researchers can now detect Alzheimer’s-related amyloid plaques in the retina of the eye. Eventually, this technology could be made available to detect Alzheimer’s early. Hearing loss can affect the quality of life for an older adult and their families, but losing the ability to distinguish sounds can be extremely challenging for the brain. If an older adult doesn’t seek treatment for their hearing, it can lead to social isolation and fewer opportunities for sensory stimulation. This can cause the auditory processing part of your brain to shrink. Losing your vision and hearing together is strongly associated with your risk of dementia.