The final report on project CHARLES by the Stress Research Intitute, Stockholm University, which investigates the effects of the new EASA FTL on pilot sleep and fatigue, was just recently published on their website.
The project used both an extensive web survey, answered by some 360 pilots, and a field study collecting data covering some 400 days of diary data. Among other findings, about one fifth of all working days were found to be associated with sleepiness up to a level that crew felt countermeasures were appropriate.
Please find the report through this link.