Biostatistics

Use this study abstract to answer the following questions: https://pubmed.ncbi.nlm.nih.gov/31162569/
Questions:
1) What is the main research question? What is the main outcome variable? What is the primary explanatory variable? What is the hypothesized relationship between these variables?
2) What is the population of interest in this study? What is the sample that was used in this study? (State the sample size and describe participants in as much detail as possible). What sampling method was used?
3) Why is this study design a good study design to help answer the main research question? What aspects of the study design are problematic or insufficient?