A recent study out of Harvard Medical School found that there was a slight, yet material difference in mortality of patients treated by older doctors as opposed to younger doctors.  In the study of hospital based internists patients of doctors age 40 and under experienced mortality of 10.8% as opposed to 12.1% mortality rate for doctors age 60 and older.  That means one additional death per every 77 patients for the older doctors.  Patient death rates for doctors in their 40s and 50s was slightly higher at 11.1% and 11.3%, respectively.

A few points of note – the study merely shows correlation and does not prove or explain causation.  It appears that a major factor is how many patients a doctor sees.  The younger doctors were closer to residency training in which time they saw a very large number of patients.  Likewise, older doctors who had more patients tended to have lower mortality. The study was of over 730,00 hospital admissions and over 18,000 doctors.

Source: http://www.bmj.com/content/357/bmj.j1797