Official websites use .gov
A
.gov website belongs to an official
government organization in the United States.
Secure .gov websites use HTTPS
A lock (
) or https:// means you've safely
connected to the .gov website. Share sensitive
information only on official, secure websites.
| Study design | High risk | Low risk | Unclear risk | Total |
| Case‐control | 3 | 2 | 18 | 23 |
| Cohort | 14 | 8 | 18 | 40 |
| RCT/CCT | 7 | 12 | 55 | 74 |
| Total | 24 | 22 | 91 | 137 |
CCT: controlled clinical trial RCT: randomised controlled trial
This table displays the overall methodological quality assessment of the included studies described in the text and represented in extended form (with all items of the tools) in Figure 1.
