Loss of Smell and Dementia: Is It an Early Warning Sign?

Large studies link a poor sense of smell in later life to a higher risk of dementia. Here's what the research shows, what it doesn't, the much more common causes of smell loss, and when to see a doctor.

By Jim Pavlish, Editor · Last updated: October 31, 2026 · Editorial policy

Short answer: several large studies have found that older adults with a poor sense of smell are more likely to develop dementia later. In one U.S. study of 4,470 older adults, people with no sense of smell had about 3.5 times the dementia rate of those with good smell. But smell loss is far more often caused by colds, COVID-19, sinus problems, allergies or normal aging, and it can't diagnose dementia on its own. If it doesn't come back within a few weeks, see a doctor.

Maybe you've noticed the coffee doesn't smell like much anymore. Or your father didn't notice the burnt toast. If you've also read that smell loss can be an "early sign of Alzheimer's," it's natural to worry.

Here's what the research actually shows, and why it's not a reason to panic.

This page is general information, not medical advice. Talk to your doctor about any lasting change in smell or memory.

The common causes come first

The NHS says changes in sense of smell are most often caused by:

• Colds, flu or COVID-19
• Sinusitis (a sinus infection)
• Allergies such as hay fever
• Nasal polyps (growths in the nose)

It can also be caused by some medicines and, rarely, by more serious conditions such as Parkinson's disease or epilepsy. The NHS adds that it's also common to lose some sense of smell as you get older, and that a changed sense of smell often gets better within a few weeks or months.

So if you've lost your sense of smell, the most likely explanation is not dementia.

What the dementia research shows

Researchers usually test smell by asking people to identify common odors from scratch-and-sniff cards or scented pens. Several long-running studies have then followed people who didn't have dementia to see who developed it.

The ARIC study (U.S., 2025). Researchers followed 4,470 older adults (average age 75, 21% Black). Compared with people who had good smell, those with moderate smell had about 1.5 times the rate of dementia, those with a reduced sense of smell (hyposmia) about 2.2 times, and those with no sense of smell (anosmia) about 3.5 times. The link held across age, race, sex and APOE4 groups. People whose smell stayed poor, or who went from normal to no smell over about 5 years, showed especially strong links.

SNAC-K (Sweden, 2023). Among 2,473 people in Stockholm (average age 70) followed for 12 years, smell problems were linked to about twice the risk of dementia, and complete smell loss to nearly three times. The risk was highest in people with smell loss who also carried the APOE4 gene, the best-known genetic risk factor for Alzheimer's (see Genetic Testing and APOE4).

Health ABC (U.S., 2017). In 2,428 Black and white adults aged 70 to 79, poorer smell was linked to higher dementia risk over 12 years in both groups, though the link was stronger in white participants.

Northern Manhattan (U.S., 2015). In a multiethnic community study of 1,037 people, lower smell test scores predicted both cognitive decline and later Alzheimer's dementia. In people without memory problems at the start, the smell test predicted decline better than a memory test did.

Why might smell and dementia be linked?

The studies above show a link, not cause and effect. Researchers describe a poor sense of smell as a possible early marker of changes in the brain, which is why it interests scientists looking for inexpensive ways to spot higher risk or to choose people for prevention trials. The Northern Manhattan researchers suggested a cheap smell test could one day help select people for treatment or prevention trials. It is not a diagnosis. (For other markers researchers use, see Biomarkers.)

The NHS also lists Parkinson's disease among the rarer causes of smell loss; Parkinson's can sometimes lead to Parkinson's Disease Dementia.

What it doesn't mean

• Most people with smell loss will not develop dementia because of it. The common causes above are far more likely.
• No smell test can diagnose dementia. Diagnosis needs a full assessment by a doctor (see Getting a Diagnosis).
• It's about risk across a group, not a prediction for any one person.

When to see a doctor

The NHS advises seeing a GP if your sense of smell doesn't go back to normal within a few weeks. The doctor will look for causes such as sinusitis or nasal polyps and may refer you to a specialist.

It's also worth mentioning to your doctor if smell loss comes with memory problems, changes in thinking, tremor or other new symptoms. Bring a list of changes and medicines (see Preparing for a Memory Appointment).

Stay safe if you can't smell well

The NHS points out that if you've lost your sense of smell, you may not be able to smell gas leaks, fires or food that's gone off. Practical steps include working smoke detectors, checking use-by dates, and asking someone else to check food if you're unsure. This matters even more for someone who lives alone with memory problems (see Living Alone with Dementia).

Common questions

Is losing your sense of smell an early sign of dementia?

It can be one of many possible early signs, but it's much more often caused by colds, COVID-19, sinus problems, allergies or aging, says the NHS. Large studies link poor smell in older adults to higher dementia risk, but smell loss on its own doesn't mean someone has or will get dementia.

How much does poor smell raise dementia risk?

In the U.S. ARIC study of 4,470 older adults, people with no sense of smell had about 3.5 times the dementia rate of those with good smell. A 12-year Swedish study found complete smell loss linked to nearly three times the risk. These are group averages, not personal predictions.

Can a smell test diagnose Alzheimer's?

No. Researchers are studying smell tests as a cheap early marker, mainly for research. Diagnosing dementia needs a full medical assessment.

When should I see a doctor about smell loss?

The NHS recommends seeing a doctor if your sense of smell hasn't returned to normal after a few weeks. Mention any memory or thinking changes too.

The bottom line

A poor sense of smell in later life is linked to a higher risk of dementia in several large, long-term studies, but it's a clue, not a diagnosis, and common harmless causes are far more likely. If smell loss lasts more than a few weeks, see a doctor, and stay safe around gas, smoke and spoiled food.

Sources

1. NHS: Lost or changed sense of smell
2. Alzheimer's & Dementia (2025): Shrestha S et al., Characterizing the olfaction and dementia association in the community-based ARIC study (PubMed 39988999)
3. Alzheimer's & Dementia (2023): Laukka EJ et al., Markers of olfactory dysfunction and progression to dementia: a 12-year population-based study (PubMed 36689643)
4. Neurology (2017): Yaffe K et al., Olfaction and risk of dementia in a biracial cohort of older adults (PubMed 28039314)
5. Neurology (2015): Devanand DP et al., Olfactory deficits predict cognitive decline and Alzheimer dementia in an urban community (PubMed 25471394)

Not medical advice. This article is general information, not a diagnosis or treatment plan for any individual. Talk with a doctor about your situation.

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