Loss of Smell Could Be Early Sign of Alzheimers Disease
The most obvious early warning sign of Alzheimer’s disease is memory loss that disrupts daily life. But another early sign could be a loss of the sense of smell, which confused researchers until a new animal study found that an abnormal protein during the very initial stages of the disease is linked to a destruction of nerve cells in the nose.
Study leader Leonardo Belluscio of the US National Institute of Neurological Disorders and Stroke and colleagues genetically manipulated mice to produce high levels of a mutated version of human amyloid precursor protein, or APP, previously associated with early-onset Alzheimer’s disease. The team found that mice making the mutant APP had four times as much olfactory nerve cell death by three weeks of age compared with normal mice.
Although it has been known that APP could be detected in the nose nerve cells of those with certain forms of Alzheimer’s disease, researchers previously thought that protein plaques commonly seen in the brains were responsible. However, in this latest researcher, the team found that APP alone, even in the absence of brain plaques, caused nasal nerve cell death.
The team also noted that when the olfactory nerve cells were blocked from producing high levels of mutant APP, more cells lived. "Reducing APP production suppressed the widespread loss of nerve cells, suggesting that such disease-related death of nerve cells could potentially be stopped," Belluscio said.
"Deficits in odor detection and discrimination are among the earliest symptoms of Alzheimer's disease. The changes…may be similar to those in other regions of the brain but appear more rapidly,” added Belluscio. “(This suggests) that the sense of smell can potentially serve as a canary in the coal mine for early diagnosis of the disease.”
“(The results) provide an exciting opportunity to explore how to prevent or reverse the events that lead to cell death and ultimately dementia,” added Dr. Donald Wilson PhD of the New York University School of Medicine, who was not involved in the study, published in the September 28th issue of The Journal of Neuroscience.
The Alzheimer’s Association lists ten signs of Alzheimer’s disease that, if noticed, should be brought to the attention of a physician:
1. Memory loss that disrupts daily life.
2. Challenges in planning or solving problems.
3. Difficulty completing familiar tasks at home, at work or at leisure.
4. Confusion with time or place.
5. Trouble understanding visual images and spatial relationships.
6. New problems with words in speaking or writing.
7. Misplacing things and losing the ability to retrace steps.
8. Decreased or poor judgment.
9. Withdrawal from work or social activities.
10. Changes in mood and personality.
Society for Neuroscience (2011, September 28). Alzheimer's protein kills nerve cells in nose; Animal study may suggest way to rescue cells from disease. Retrieved from ScienceDaily, September 30, 2011
Alzheimer’s Association, 10 Signs of Alzheimer’s.