Sex-change operations will now be covered by Medicare after a federal health department appeals board on Friday struck down a 33-year-old policy excluding the procedures. The ruling, a major victory for LGBT rights advocates, may have a ripple effect through the private insurance industry.

"The Board has determined that ... denying Medicare coverage of all transsexual surgery as a treatment for transsexualism is not valid under the reasonableness standard the Board applies," wrote the Department of Health and Human Services Appeals Board in a ruling, posted online by Buzzfeed. "The NCD was based on information compiled in 1981."

In 1981, they said, the procedure was still considered "experimental" and "controversial." As more evidence emerged that the procedure is safe and necessary, a 74-year-old Army veteran named Denee Mallon brought a challenge to the appeals board in 2012. Despite having a doctor's recommendation to have the sex-change operation, Medicare denied Mallon's claim.

The American Medical Association has said that these procedures are legitimate medical treatments for a known disorder and that it opposes the denial of health insurance based on gender identity. According to its policies on LGBT issues, the AMA writes that it "supports public and private health insurance coverage for treatment of gender identity disorder as recommended by the patient’s physician."

But until now, the government had been using decades-old medical wisdom to guide its policy. "Because of the lack of well controlled, long term studies of the safety and effectiveness of the surgical procedures and attendant therapies for transsexualism, the treatment is considered experimental," the Centers for Medicaid and Medicare still says in its bylaws. "Moreover, there is a high rate of serious complications for these surgical procedures. For these reasons, transsexual surgery is not covered."

In its ruling, the board writes that studies over more than three decades were at odds with the idea that transsexual surgery is experimental. They called the procedure "safe, effective and indisputably necessary" for people suffering from gender identity disorder — those who were born with a sex that conflicts with their gender identity. Recognized by the Diagnostic and Statistical Manual of Mental Disorders, gender identity disorder places people at risk of depression and suicide if left untreated.

The board's decision will not immediately grant coverage to all who apply, but it means that the government cannot automatically deny patients when they make claims.