Complex sentence: He is a Research Director in the French National Centre for Scientific Research (CNRS) and a senior research fellow in the Institute for Research and Information in Health Economics (IRDES), a French research institute specializing in health economics and health statistics.
Split into simpler sentences: He is a Research Director in the French National Centre for Scientific Research (CNRS). Previously, he had been a senior research fellow in the Institute for Research and Information in Health Economics (IRDES), a French research institute specializing in health economics and health statistics.