Scientifically speaking: Your nose knows best

What most people still don’t realise is that losing your sense of smell might predict something far more serious than a viral infection

The honeydew tasted like a sugary potato. That was my first clue that something was wrong.

Anosmia was the single indicator that I might’ve caught an infection (PTI)

I pride myself on having a keen sense of smell (sometimes to my disadvantage in putrid places), but overall it has served me well. So, you can imagine my dismay when, just days after returning from Thailand last year, I temporarily lost my sense of smell. As the American saying goes, the best part of coffee is waking up to smell it.

Anosmia was the single indicator that I might’ve caught an infection. I immediately bought a smell training kit online with vials of lemon, clove, eucalyptus, and rose, and whiffed them regularly, morning and night. Fortunately, my sense of smell returned to normal within weeks, and I soon forgot about that chapter.

But many others aren’t so lucky. The Covid-19 pandemic thrust anosmia into public consciousness, revealing how common and distressing smell loss can be. Before the pandemic, many people didn’t even know that infections could steal this sense. Now we know that weird misfiring of smell is a hallmark of Covid and its aftermath, with many never fully regaining what they’ve lost.

What most people still don’t realise is that losing your sense of smell might predict something far more serious than a viral infection. As neurobiologist Michael Leon from the University of California, Irvine, recently said in an article on the sense of smell in New Scientist: “By middle age, your all-cause mortality can be predicted by your olfactory ability.”

This astounding claim seems to be backed by science. A landmark study following over 3,000 older people found that 39% of those with complete smell loss died within five years, compared to just 10% of those with normal smell. After accounting for other health factors, anosmia emerged as a surprisingly strong predictor of five-year mortality, perhaps comparable to heart failure, diabetes, or even cancer.

To be clear, losing your smell doesn’t doom you to an early death. Rather, it’s a warning that something else might go wrong.

The connection goes beyond mortality. Losing the sense of smell has been linked to more than 100 conditions, from Parkinson’s and Alzheimer’s to cardiovascular disease and arthritis. The worse your sense of smell, studies show, the worse you perform on cognitive tests.

Why would smell loss predict dire outcomes? The answer lies in our nose’s unique wiring. Unlike other senses that route through the brain’s central relay station, smells take the express lane directly to regions controlling emotion, memory, and decision-making. This superhighway explains why certain scents can instantly transport us to childhood memories. When it breaks down, we lose a vital source of mental stimulation.

The olfactory system also serves as an early warning system. Pathological proteins associated with neurodegenerative diseases accumulate in smell-related brain regions years before classic symptoms appear. Meanwhile, our nose’s direct exposure to the environment makes it vulnerable to collective damage from pollution and pathogens—damage that may reflect broader health problems.

In other words, your nose is the canary in the coal mine for your health. When it stops working properly, it might be telling you about inflammation lurking elsewhere, stem cells that aren’t regenerating like they used to, or even everyday dangers you can no longer detect.

Given these implications, I find it remarkable how little we value this sense. Surveys consistently show people would rather give up smell than their smartphones. Yet emerging research suggests we should be paying much more attention to our noses.

The good news is that smell training appears to work. Studies show that people who regularly sniff distinct odours can improve their olfactory sensitivity. One intriguing study even found that people exposed to different scents while sleeping showed dramatic improvements in memory, though we need more research to know if this works for everyone.

And speaking of Parkinson’s, the diagnostic power of smell works both ways. While losing your sense of smell can signal health problems, some people possess an extraordinary ability to detect disease through scent. Joy Milne, a Scottish nurse, noticed her husband’s body odour had changed to a “musty” smell 12 years before he was diagnosed with Parkinson’s disease. When she later attended a support group and realised everyone with Parkinson’s had the same distinctive scent, she approached researchers who confirmed her ability. She could identify Parkinson’s patients by smell alone, even detecting one case well before clinical symptoms appeared.

My own brief episode of smell loss gave me a glimpse into this hidden world. Those days of bland coffee and flavourless food felt like living in a muted reality. Now, when I smell my coffee brewing, I’m reminded that the signs of good health might be right under our noses.

Anirban Mahapatra is a scientist and author, most recently of ‘When The Drugs Don’t Work: The Hidden Pandemic That Could End Medicine’. The views expressed are personal.