A simple sniff test can help in the early diagnosis of Alzheimer’s disease. Combined with standard cognitive tests, it enhances the ability to identify the disease before there are any other symptoms. That means better care.

Background: Brain degeneration can begin as early as 10 years before a definitive diagnosis. Many people develop mild cognitive impairment (MCI) first—a condition marked by problems with memory and thinking that are not serious enough to affect daily functioning. Many people with MCI don’t know they have it—and while having MCI increases your risk of developing Alzheimer’s, it’s not a sure thing. Better tests are needed to identify people with MCI in the first place…and to figure out which ones are at highest risk for Alzheimer’s.

Smell might be key. A sharp decline in the sense of smell is one of the earliest warning signs—areas in the brain that process odors are often the first to be affected by the disease. Smell affects taste, too—one reason why many Alzheimer’s patients often complain that food doesn’t taste as good as it once did. So researchers decided to test a commercially available “sniff” test to see if it could improve early diagnosis.

Study: Researchers at University of Pennsylvania studied 262 people with Alzheimer’s disease, 198 with mild cognitive impairment and 292 healthy older adults. On average, subjects were in their early-to-mid-70s. Some with MCI were further classified based on the severity of their condition, since people with more severe memory loss and other symptoms are more likely to progress to Alzheimer’s.

Each participant had been painstakingly diagnosed by an experienced clinician using a battery of tests including neuroimaging and advanced cognitive testing. Then researchers used the “Sniffin’ Sticks Odor Identification Test,” which asks participants to identify 16 common odors and takes about eight minutes. Everyone also took a standard cognitive test called the Montreal Cognitive Assessment (MoCA). It’s a one page, 30-point test that measures such skills as short-term memory recall. A health professional can give it in about 10 minutes.

Findings: The healthy older adults did best on the smell test, followed by those with MCI, followed by those with Alzheimer’s. Within the MCI group, the test also sniffed out those most at risk—patients on the milder side did better identifying odors than those who were more impaired.

Surprising finding: The sniff test was pretty good on its own but it really made a difference when combined with MoCA, the standard cognitive test. By itself, MoCA correctly identified 77% of those with mild cognitive impairment and 93% of those with Alzheimer’s. Add the sniff test, and the accuracy rate went up to 92% of those with MCI and 98% of those with Alzheimer’s.

Bottom Line: This finding may change the landscape of Alzheimer’s screening, making it easier to identify people at highest risk of developing the disease quickly and relatively inexpensively. Here’s why that matters: Knowing you’re at high risk means you can get targeted medical care if symptoms develop, work with your doctor to stop taking medications that can increase dementia risk, improve lifestyle factors linked to improved cognition, make plans for future care and finances—and perhaps sign up for new clinical trials in the future.  That’s why an annual “cognitive checkup” is now covered by insurance.

Should you try the sniff test yourself? You could buy it—it’s commercially available and easy to self-administer—but it’s pricey ($325 for a 12-odor version), and best given along with cognitive testing, as this study showed. If your doctor orders it, it’s at least possible that insurance might pick up all or part of the tab.

Do see your doctor if you find that your sense of smell or taste seems to be declining. Rest assured—a loss of smell or taste can be caused by many things other than incipient dementia, including medical problems such as a thyroid condition, certain drugs such as nasal steroid sprays, even a zinc deficiency. Best to find out.