A declining sense of smell is recognised as one of the early signs of cognitive decline, before the clinical onset of Alzheimer’s disease. New research has shown that this symptom could be used to determine if patients with mild cognitive impairment (MCI) may respond to drugs (called cholinesterase inhibitors) to treat Alzheimer’s disease.
Cholinesterase inhibitors have shown some effectiveness in improving the cognitive symptoms of Alzheimer’s disease. However, they have not been proven effective as a treatment for individuals with MCI, a condition that markedly increases the risk of Alzheimer’s disease.
During a year-long study at Columbia University Medical Centre, 37 participants with MCI underwent odour identification testing before and after using an atropine nasal spray that blocks cholinergic transmission.
The patients were then treated with the new drug (donepezil) for 52 weeks, and were periodically reevaluated with memory and cognitive function tests. Those who had a greater decline, indicating greater cholinergic deficits in the brain, after using the anticholinergic nasal spray test saw greater cognitive improvement with the drug.
In addition, short-term improvement in odour identification from baseline to eight weeks tended to predict longer-term cognitive improvement with donepezil treatment over one year.
Dr. Devanand, the study’s lead author, said: ‘These results, particularly if replicated in larger populations, suggest that these simple inexpensive strategies have the potential to improve the selection of patients with mild cognitive impairment who are likely to benefit from treatment with cholinesterase inhibitors like donepezil.’