Could your ability to identify smells predict how well you could recover from cardiac surgery? Johns Hopkins neuropsychologist Vidya Kamath recently published a study in International Journal of Geriatric Psychiatry suggesting just that: Older people who were found to possess an impaired sense of smell before surgery were more likely to experience delirium after their operation.

Postoperative delirium is the most common complication of surgery for older adults, according to the American Geriatrics Society. During this state, patients can experience confusion, disorientation, persistent sleepiness, hallucinations, agitation and aggression.

An expert on the neuropsychology of smell, Kamath last year authored a study in Journal of Gerontology showing a link between a decreased sense of smell and the risk of developing late-life depression.

Her current report focused on older people who were undergoing cardiopulmonary bypass surgery at Johns Hopkins. Their average age was 70. Of the 189 patients who were studied, 30% came to surgery with deficits in olfaction. Previous research shows that people with diminished cognitive functioning are more likely to become delirious. In this study, even after accounting for cognition, the smell-impaired were 2.25 times more likely to develop delirium after surgery compared to patients with normal smell.

Kamath points out that as many as 50% of cardiac surgery patients can experience postoperative delirium, with a higher incidence in older adults. Presurgical olfactory tests measuring a person’s ability to detect, identify or discriminate odors, she says, could help spot high-risk patients for whom early intervention and preoperative rehabilitation strategies might prove valuable.

“As we become more familiar with the type of problems that older adults can have after surgery, there have been more large-scale efforts to screen for important risk factors,” she says, noting that a comprehensive evaluation of a patient’s potential risks should look at such factors as frailty and cognitive dysfunction as well as sense of smell.

Johns Hopkins anesthesiologist Charles Brown IV, senior author on the recent study, estimates the postoperative delirium cases he encounters each year have declined about 25% since he entered the field in 2011. He attributes the reduction to reduced use of “deliriogenic” medications during and after surgery, and comprehensive efforts to improve pain control, remove breathing tubes as early as possible, and encourage sleep at night and ambulation during the day.

Brown says in-depth cognitive screening, including olfactory testing, has yet to be standardized and implemented nationally. “It could give us a window into people's brain vulnerability and the potential risk of delirium and future cognitive decline in older adults,” he says, noting that in longitudinal studies of “cognitively intact” older adults, olfactory loss is an independent predictor of transition to dementia.