A dementia diagnosis usually starts with a family member noticing that something isn’t quite right: a partner becoming forgetful, a normally placid parent losing their temper more often. From there, there are doctor’s appointments—memory and behavior tests that haven’t changed in years, brain scans if the money is there, or one of the battery of new blood tests looking for the biomarkers of brain damage. And then: nothing.

Neurodegenerative diseases like dementia and Alzheimer’s are more feared than cancer and heart disease combined, according to a 2016 survey, and one of the most frightening things about them is how little we still know. There are no cures, and few effective treatments.

So you might question the benefits of a 5-minute test that can assess your risk of getting dementia before you show any symptoms. The Integrated Cognitive Assessment (ICA) test, developed by the British startup Cognetivity Neurosciences, has been granted Food and Drug Administration clearance to be marketed in the United States and is being trialled at several NHS trusts in the UK. But is there any point in taking a test for a disease you can’t do anything about?

The ICA is designed as a “semi-supervised” screening test, says Cognetivity CEO Sina Habibi. It could form part of an annual health check-up for the over-50s, looking for the earliest signs of neurodegenerative disease before they become apparent in behavior. “In the same way you look at blood pressure, you could look at the brain with a cognitive test to see if there’s something malfunctioning,” he says.

An early diagnosis could help people plan ahead and put their affairs in order—but arguably that’s something they should probably be doing anyway. Lifestyle tweaks such as eating less fat, exercising more, or drinking less can also reduce risk, particularly in vascular dementia, which is caused by poor blood supply to the brain and is therefore closely linked to heart health.

The procedure runs on an iPad. A zebra appears onscreen and then disappears, replaced by a railway bridge. There are flashes of beach scenes in black and white, and then a glimpse of an exotic bird, all interspersed with monochrome grids and fuzzy static—a captcha at warp speed. The user’s task is simple: They tap on the right side of the screen whenever they see an animal in one of the pictures, and on the left side when they don’t.