Restricting mandatory overtime is not the most effective way to keep nurses from being overworked, according to new research. Laws that limit the number of consecutive hours worked were found to be better in keeping patients and nurses safe.

About half the U.S. nursing workforce is subject to at least one of these policies, the study authors noted. However, “few studies” have investigated their effectiveness. The topic is important because a “consensus” has emerged that working unreasonably long hours endangers both nurses and patients, the researchers stated.

While legislation varies by state, mandatory overtime laws typically allow nurses to refuse to work overtime except in emergencies. These laws result in about a 4 percentage-point decrease in the likelihood that nurses will work mandatory overtime, the researchers determined after controlling for differences in state nursing workforces. This is a significant effect, given that about 9% of registered nurses worked mandatory overtime in 2008.

However, consecutive hour laws had an even greater effect. These laws generally set limits on shift length and hours between shifts — for instance, stating that a nurse is allowed to work only 12 hours out of every 24. These laws are associated with an 11.5 percentage point decrease in the likelihood that a nurse will work more than 40 hours a week, the researchers found.

“The consecutive work hour policy appears to be a better regulatory tool for reducing long work hours for nurses,” they concluded.

Their findings were based on an analysis of the National Sample Survey of Registered Nurses, a survey conducted by the federal government every four years. The researchers examined 2004 and 2008 data, from a total of more than 14,600 registered nurses. The results are published in Health Services Research.