The most important part of mental performance that may be impacted is awareness of things going on around you, because this can be a safety hazard, especially w

The most important part of mental performance that may be impacted is awareness of things going on around you, because this can be a safety hazard, especially while driving. Unfortunately, it's also hard to detect, because when you don't notice something you don't notice that you don't notice it. However, ability to focus may be a good proxy. Can you pay attention to someone for as long as you used to be able to without having your mind wander? Note that being able to focus on a specific thing, like your work, doesn't mean that you're not impacted. According to research, the ability to focus is a depletable resource, and you could be pulling focus from one area to maintain another. See if there's anything in your life, like reading a book, doing chores, or talking with your significant other, where your focus is notably impacted in quality or duration. Once you've made sure you're not going to nod off on the freeway, you can start focusing on whether your ability to work may be impaired. Priorities!