In order to begin your systematic review you will need to formulate your research question.

You will want to identify whether there is enough research on the topic to warrant a systematic review - too few studies will mean there may not be enough data to synthesise. In this case you may have to broaden your question, for example by expanding the population you are looking at.

Alternatively, if your question is too broad, you could consider revising the scope of your question to have a narrower focus, or consider another more suitable review type, such as a scoping review, which is designed to provide a broad overview of a topic area rather than answering a specific and targeted question.

Your research question should:

• be narrow and specific enough to accurately and succinctly outline your line of inquiry
• be clearly answerable from the studies included in your review, and you should aim to retrieve "all" the relevant literature on the topic you have chosen
• specify the variables and population that are being studied

Methley, A.M., Campbell, S., Chew-Graham, C., McNally, R. and Cheraghi-Sohi, S., 2014. 'PICO, PICOS and SPIDER: a comparison study of specificity and sensitivity in three search tools for qualitative systematic reviews', BMC Health Services Research, vol. 14:579. https://doi.org/10.1186/s12913-014-0579-0

Mellor, L., no date. 'How to formulate the review question using PICO. 5 steps to get you started', Covidence [Blog]. https://www.covidence.org/blog/how-to-formulate-the-review-question/