Does losing the sense of smell mean mild cognitive impairment will become dementia?
Losing your sense of smell (olfactory decline) is a known early sign of brain changes linked to Alzheimer's disease and other dementias. In people with mild cognitive impairment (MCI), smell loss can signal a higher risk of progressing to dementia, but it is not a certainty. Research shows that smell decline often happens alongside memory loss and brain changes, but many factors influence whether MCI turns into dementia.
What the research says
A large study following older adults for nearly 8 years found that those who lost their sense of smell were more likely to develop MCI and dementia 5. The study showed that smell decline was linked to faster memory loss and more brain pathology after death 5. This suggests that smell loss is an early marker of the disease process, not just a harmless symptom.
Another study in Gulf War veterans found that those with worse smell test scores also had lower cognitive scores, and smell loss was associated with a higher risk of MCI 9. This supports the idea that smell and cognition are connected.
However, not everyone with MCI and smell loss will develop dementia. The brain is complex, and other factors like age, genetics, and overall health play a role. For example, some people with MCI remain stable for years, and some even improve 5. Smell loss is a risk factor, not a guarantee.
Other research on MCI focuses on treatments like nutritional supplements, cognitive training, or plasma exchange, but these studies do not directly address smell loss as a predictor 146. The strongest evidence linking smell decline to dementia comes from the long-term study mentioned above 5.
What to ask your doctor
- Should I have a formal smell test to track changes over time?
- What other tests (like brain imaging or memory assessments) can help determine my risk of progressing from MCI to dementia?
- Are there lifestyle changes or treatments that might slow cognitive decline, even if I have smell loss?
- How often should I follow up to monitor my memory and smell function?
- Can other conditions (like sinus problems or COVID-19) cause smell loss that is not related to dementia?
This question is drawn from common patient questions about this topic and answered using cited medical research. We do not provide individualized advice.