Just a humble input, not study. You are right that cognitive load should be minimal so this results in more reliable information from user. In general question is better because user have to mentally transform statment to question and then answer it.
But you may see that web forms (and not only) are mostly made with short labels and not with questions. This is not only because of lack of place. The main reason is to ask as most as exact what you need. For example, to answer your question "How long have you had a driver's license?" (suppose in years) user need to remember year when ne obtain his license and than make ariphmetic calculation. This is a kind of brain loading. The statement "Your driver's licence experience" is not also one step in thinking - are you about date of formal license receiving or about real practical experiense? Also user are guessing why are you asking so he may provide unreliable answer. And if you write "Your driver's license issue year:" probably you'll receive concrete answer and more important - you can check it as well as make all needed calculations by yourself correctly in the future as you need not to link user's data with the date of asking.
But in some cases you should ask the question and then prompt the statement you provided in very long questionnary to test if user provide you with correct information.