*2.5. Quality Assessment*

The Newcastle–Ottawa Scale (NOS) was used to assess the quality of non-randomized studies [29]. The quality of included studies was evaluated in the following three major components: selection of the study group (0–4 points); quality of the adjustment for confounding (0–2 points); and assessment of the outcome of interest in the cohorts (0–3 points). A higher score represented better methodological quality.
