That would be Desai, et al. Though I can't access the paper right now, they say that the 2011 regulations have tripled handoffs, increasing handoff risk. It also turned out that the average amount of sleep per week was not increased by much after instituting the regulations.
[2] Desai SV, Feldman L, Brown L, et al. Effect of the 2011 vs 2003 Duty Hour Regulation–Compliant Models on Sleep Duration, Trainee Education, and Continuity of Patient Care Among Internal Medicine House Staff: A Randomized Trial. JAMA Internal Medicine, 2013; DOI: 10.1001/jamainternmed.2013.2973
[1] https://www.sciencedaily.com/releases/2013/03/130325183819.h...
[2] Desai SV, Feldman L, Brown L, et al. Effect of the 2011 vs 2003 Duty Hour Regulation–Compliant Models on Sleep Duration, Trainee Education, and Continuity of Patient Care Among Internal Medicine House Staff: A Randomized Trial. JAMA Internal Medicine, 2013; DOI: 10.1001/jamainternmed.2013.2973