Systematic reviews and meta-analyses: evaluating the evidence behind expanding methodologies

Finding answers to scientific questions in the field of occupational medicine is a multi-stage process. An important, preliminary, and sometimes sufficient approach is to conduct systematic reviews and meta-analyses. Undoubtedly, systematic reviews and meta-analyses can represent an efficient and effective way to interpret research that has already been conducted. These could provide adequate information to the occupational physician or whoever decides the strategy. On the other hand, for the researcher, the outcome of a systematic review and meta-analysis can help design further primary research, but it can even lead to challenging the conclusions, especially if they reveal flaws in their design or execution. Therefore, it is important that the occupational physician has the skills to challenge systematic reviews and meta-analyses where and when necessary. On one hand, systematic reviews and meta-analyses can be so restrictive in their inclusion criteria that crucial data may be overlooked. On the other hand, they may depend on inadequate standards for evaluating the quality of the studies they include. It is unlikely that a meta-analysis is more effective than the primary research it is based on. Furthermore, it is very rare for primary research studies to be identical, and systematic reviews and meta-analyses may not recognize the best way to manage this heterogeneity. Therefore, systematic reviews and meta-analyses can have a number of biases or flaws, just like other forms of research. However, the negative consequences of such errors in systematic reviews and meta-analyses on the science and practice of occupational medicine can be greater (compared to errors in other research), as they are often dangerously perceived as a definitive judgment from the “Supreme Court” on a matter. Systematic reviews and meta-analyses should therefore be verified. Nowadays, many follow guidelines such as Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) and Meta-analyses of Observational Studies in Epidemiology (MOOSE), and are registered in the International Platform of Registered Systematic Reviews and Meta-analysis Protocols. The report will examine the key aspects of the above, using relevant and important published studies as examples, such as stress and burnout at work and the protection of workers from COVID-19 and similar risks.