A study by Dr. Aiken found that patients scheduled for routine surgery were 31 percent more likely to die in a hospital with a patient-to-nurse ratio of eight to one than in a hospital with a ratio of four to one. The study was published last year in The Journal of the American Medical Association.
There are probably vast differences, particularly in the wealth of the facility and the patient population, between low ratio and high ratio institutions. So the results are noteworthy but not conclusive -- as with all studies of this nature.
That said, I have a strong belief that overburdening health care workers increases error rates. (Duh!) Nursing is under particular stress. It is a peculiar profession in the combination of shift work, physical demands, emotional burden, and cognitive and training requirements. Medicine is not nearly so physically demanding. A paraplegic physician can excel at a very wide variety of work in almost all settings, a paraplegic nurse would probably not do direct patient care. It is not surprising that the role cannot be filled at any affordable price -- particulary as the US population ages. It is hard to be 55 and moving patients around.
Nursing will have to split into several different roles with different training requirements. In particular I think a lot of the physical aspects of nursing, which are often very satisfying to care providers, may shift to other workers.