When you look at the battery use, the figures always add up to 100% of the battery used. So if you have 95% batter left, you would still see screen 50%, OS 25%, etc. That's info just for perspective.
Typically, you see screen #1 followed by OS #2. If you see them both around the same mark, you can't draw the conclusion that the OS is somehow extra active. It's more likely the screen has been used less, so the screen % drops (say it drops from 55% to 45%), and everything else necessarily increases a little (they each need to increase to make up for the other 10%). The OS is the second most active thing, so that ends up looking like it increased, when really the screen just decreased.
Just something to consider.