Understanding and honoring patients’ medical decisions can be made difficult due to conflicting state laws, a new study has found. Researchers anticipate the issue will grow along with the nation’s booming senior population.

In a first-of-its-kind study of medical decision-making rules, researchers with Beth Israel Deaconess Medical Center, the Mayo Clinic and the University of Chicago reviewed laws from all 50 states regarding the medical choices of patients. Their findings, published Thursday in the New England Journal of Medicine, show a conflicting system of rules that’s difficult to navigate and may impede honoring patients’ wishes.

Thirty states require the “alternative decision makers” of patients to contain an ability to make difficult medical decisions, such as withdrawing a feeding tube or other life-sustaining treatment. But there’s no way to assess that ability, the review said. Thirty-five states employ a “surrogacy ladder,” which creates a hierarchy of people able to make medical decisions when patients don’t have a power of attorney. But even those systems vary when it comes to the types of decisions surrogates can make.

“One important message from this study is that, in the absence of a clearly identified spokesperson, the decision-making process for incapacitated patients may vary widely depending on where they live,” said senior researcher Daniel B. Kramer, M.D., MPH, in a release on the study.

The study also found states varied in how they defined an appropriate decision maker. Some require surrogates to have an in-depth knowledge of a person’s beliefs, while others only require the decision maker be an adult.

The biggest takeaway from the review, according to the research team, is that despite ongoing disputes in healthcare facilities about patients’ decisions, no nationwide standard or guide exists for family members or providers.

“Decisions about withdrawing or withholding life-sustaining care are incredibly emotional and challenging,” said study author Erin Sullivan DeMartino, M.D., with the Mayo Clinic. “But when there is ambiguity about who is responsible for decision-making, it adds much more stress to that moment.”