Sense of Smell Linked to Cognition.

• Position: DEMENTIA

Seniors who can identify smells like roses, turpentine, paint-thinner, and lemons, and have retained their senses of hearing, vision, and touch, may have half the risk of developing dementia as their peers with marked sensory decline.

In a study by the University of California, San Francisco, researchers tracked close to 1,800 participants in their 70s for a period of up to 10 years to see if their sensory functioning correlated with the development of dementia. At the time of enrollment, all participants were dementia-free, but 328 participants developed the condition over the course of the study.

Among those whose sensory levels ranked in the middle range, 141 of the 328 developed dementia. This compares with 83 in the good range and 104 in the poor range.

Previous research has centered on the link between dementia and individual senses, but the researchers' focus in this study was on the additive effects of multiple impairments in sensory function, which emerging evidence shows are a stronger indicator of declining cognition.

"Sensory impairments could be due to underlying neurodegeneration or the same disease processes as those affecting cognition, such as stroke," says epidemiologist and first author Willa Brenowitz of the Department of Psychiatry and Behavioral Sciences, and the Institute for Neurosciences.

"Alternatively, sensory impairments, particularly hearing and vision, may accelerate cognitive decline...