Slim says it tracks his advancing age--and his declining mental acuity.

FORBES: Magazine Article

Although one of the other 11 members of the jury was, improbably, also a historian of science, two and possibly a third showed the mental acuity of fireplugs.

ECONOMIST: American juries

In particular, you would need to measure their ability to perform different tasks in a standardized way, such as walking on a treadmill, ability to lift weights, mental acuity etc.

FORBES: Getting The Benefits Of Red Wine From A Pill? Not Likely.