**2. Methods**

This paper is a systematic review compiled of cross-sectional and longitudinal studies. The findings of the articles were presented into a narrative synthesis. An extensive search strategy was adopted to identify relevant papers using applicable terms and synonyms. The process involved a critical evaluation of relevant papers and steps to be followed such as searching databases according to the inclusion/ exclusion criterion, data extraction and quality assessments of relevant papers. An electronic database named PROSPERO was also searched to identify pre-existing systematic reviews within the chosen topic to minimise any potential bias and identify the 'grey literature'. The selection strategy of papers was divided into categories comprising of population, exposure, comparator and outcome(s), shown in **Figure 1**.
