Migrant workers occupational health research: an OMEGA-NET working group position paper.

"Declarations Conflict of interestThe authors declare that they have no conflict of interest. Conflict of interest The authors declare that they have no conflict of interest."

"This paper was written within the scope of OMEGA-NET, supported by COST (European Cooperation in Science and Technology), project CA16216: Network on the Coordination and Harmonisation of European Occupational Cohorts. Prospective surveys of migrants may be hard to successfully conduct because of low response rates and attrition particularly of temporary workers. Registry-based studies are helpful in this context. The strengths of registry-based studies are that they can be conducted using a longitudinal design, using objectively collected data, which enables causal inferences (Thygesen and Ersbøll ). Moreover, registry-based studies are less likely than surveys or qualitative studies to suffer problems of language and cultural barriers. Some Scandinavian countries have national registers which include data on migrants. The shortcomings of registry-based studies include that researchers cannot influence the data that are collected and there is limited ability to control for confounders and they are unlikely to include undocumented migrants. The strength of survey and qualitative studies, are that data collection can be tailored to the research questions of the particular study."