“(Every extra doctor or nurse patient causes 4% - 7% death risk increase, each)”
You have it backwards!
Every extra bed a doctor doctor or nurse patient has to cover causes 4% - 7% death risk increase.
Every extra doctor’s patient or nurse’s patient ups the risk 4-7%.
This is an example of reading comprehension.
Article means that when there is a higher amount of patients to doctors the mortality rate rises by 4%.
For Nurses 7%.
It does not mean when there are more Doctors or Nurses there is a higher mortality rate.