PROBLEMS identifying common odours may precede cognitive decline in older adults, a study has shown.
Researchers studied 589 older adults with an average age of 80 who did not have cognitive impairment in 1997 and asked them to conduct smell identification tests where 12 familiar smells were placed under their nose.
They had to match each smell to one of four possible alternatives and received a score from one to 12 based on the number of correct responses.
The test was repeated every year for five years and participants underwent an examination including a cognitive function test afterwards.
Over the course of the study, 177 people, 30% of the study group, developed some form of mild cognitive impairment.
Results showed people that scored below eight on the odour tests were 50% more likely to develop cognitive impairments and low scores were associated with rapid decline in episodic memory, semantic memory and perceptual speed.
Authors speculated that the onset of Alzheimer's may be heralded by 'tangles' developing in areas of the brain associated with processing smells.
Archives of General Psychiatry (2007) 64: 802-808