How many patients per R.N. is ideal is a complicated hospital management question with conflicting research support. A new European study may further muddy the waters.

The observational study collected data from 300 European hospitals in nine countries and found that an increase in a nurses' workload by one patient increased the likelihood of an inpatient dying within 30 days of admission by 7 percent. However, more nurse education mitigated this effect. For every 10 percent increase in the number of nurses with bachelor’s degrees, the patient mortality risk decreased 7 percent.

Although the findings are correlational and therefore cannot prove causation, they are likely to play a role in the ongoing debate about the right nurse-to-patient ratios. Trained staff represents one of the highest costs for hospital operators in both Europe and the United States, and not surprisingly, there is a difference in views between organizations that represent nurses and the health care providers that employ nurses about what the ideal ratio should be.

The study, which was published in The Lancet, seeks to inject some data into the debate over staffing ratios. The researchers looked at discharge data for nearly half a million patients aged 50 years or older who underwent common surgeries. They adjusted risk factors by age, sex, admission type, surgery type and patient comorbidities. Then they used surveys to measure nurse staffing and nurse education at the facilities where the patients were treated.

How generalizable the results are to U.S. hospitals may be debatable, as nurse-to-patient ratios are often higher in European countries with government controlled health care systems. However, another study documenting a link between more educated nurses and lower nurse-to-patient ratios will certainly be greeted warmly by nursing organizations in the United States.