This easy Alzheimer's test from Ohio State University is simple, accessible and you can do it right now.
From the Ohio State website:
The Self-Administered Gerocognitive Exam (SAGE) is designed to detect early signs of cognitive, memory or thinking impairments. It evaluates your thinking abilities and helps physicians to know how well your brain is working. You do not need special equipment to take SAGE - just pen and paper. There are four forms of the SAGE test. You only need to take one. It doesn't matter which one you take; they are all interchangeable.
You can do the test on their website by clicking here.