Frame your question by relating to PICOS:
PICOS is a well used, standard model for framing.
The Centre for Reviews and Dissemination, University of York, have produced a guide which includes further details on PICOS and its use:
Use the results from your initial searches to refine your search terms. When you have decided upon your final search terminology (inluding publication date ranges and other limitation criteria), carry out the search through each database in turn noting the number of results. This information will be added to your report.