Patients with sickle cell disease (SDC), a disorder of the red blood cells, face a range of complications, such as damage to the liver, heart, and kidneys, vision loss, acute chest syndrome, anemia, and hand-foot syndrome that only worsen over time, according to the Centers for Disease Control and Prevention. The national average life expectancy for people with this disease ranges from only 42 to 47 years, but a new case study has found four female patients who have lived almost twice the average, stated a news release.

Report author Dr. Samir K. Ballas, Professor Emeritus in the Department of Medicine at Sidney Kimmel Medical College, believes their prolonged life expectancy may have resulted from their healthy lifestyles and strong relationships. “All of the women were non-smokers who consumed little to no alcohol and maintained a normal body mass index. This was coupled with a strong compliance to their treatment regimens and excellent family support at home,” Ballas said in the release.

In the case study, published in Blood, American Society of Hematology, the definition of family support was a spouse or child looking after and caring for their loved one. Each of the four women had a mild form of SCD, but had all suffered from complications from their disease. “For those with mild forms of SCD, these women show that lifestyle modifications may improve disease outcomes,” Ballas said in a press release.

Being a genetic disease, SCD is caused when a child inherits a sickle gene from both parents. If a single sickle gene is inherited from only one parent, they have a sickle cell trait (SCT) and usually live a normal life, but they have the chance to give this trait to their children. When a child inherits SCD, their red blood cells, responsible for carrying oxygen throughout the body via small blood vessels, become tough and sticky, forming a sickle shape similar to the farming tool. This causes the red blood cells to become clogged when trying to move through small blood vessels, according to the CDC.

“These women never had a stroke, never had recurrent acute chest syndrome, had a relatively high fetal hemoglobin count [which helps to prevent cells from sickling], and had infrequent painful crises,” Ballas said in the release.

Ballas points out this study included only four female participants; females with SDC live longer than males, and currently it’s not known why. The only treatment approved by the United States Food and Drug Association for SDC is hydroxyurea, but due to the mild nature of their disease, none of the women in this study were eligible to receive this treatment. Ballas wants SDC patients to see these four women as positive examples for beating the odds, and achieving a high quality of life.

“I would often come out to the waiting room and find these ladies talking with other SCD patients, and I could tell that they gave others hope, that just because they have SCD does not mean that they are doomed to die by their 40s,” Ballas said in a press release.

Read more: The HemeChip Detects Sickle Cell And Other Blood Diseases In A Flash, May Help Developing Nations

Ballas S, Pulte D, Lobo C, Riddick-Burden G. Case series of octogenarians with sickle cell disease. Blood, American Society of Hematology. 2016