Considering 30 is pretty much the lower bound for becoming a physician, that stat sounds a little bit like "40% of employee absences happen on Mondays and Fridays". Alarmist and of zero value.
I thought about that, but it is indeed getting worse. If a doctor works from 30-70 (not sure what the average retirement age would be), then about 38% should be over 55. Clicking through to the actual statistics:
Percentage of active physicians aged 55 or older: 46.7% for 2021, 44.9% for 2019, 44.1% for 2017, 43.2% for 2015, 42.6% for 2013, 40.3% for 2010, 37.6% in 2007.
So that is a worrying trend, since increasing population should result in at least a steady state, if not decreasing average age.
Also, depends on specialty. 92.4% (!!) of specialists in pulmonary disease are over the age of 55. So I hope the aging population doesn't have any lung problems.