Sickle cell anemia is an inherited blood disorder. It is caused by a mutation in the gene encoding for hemoglobin, the protein in red blood cells that binds to oxygen so it can be transported throughout the body.
The abnormal hemoglobin causes disc-shaped red blood cells to deform into a crescent- or sickle-like shape, causing them to become easily trapped in narrow blood vessels and to be much more quickly broken down and die. Clumps of sickled red blood cells can block blood vessels, preventing blood from flowing and carrying oxygen throughout the body, and causing inflammation and damage to the vessels.
Life expectancy
Several studies in past years have assessed the average life expectancy of a patient with sickle cell anemia, but new treatments are changing expectations and new studies are needed. One often used as a baseline is the Cooperative Study of Sickle Cell Disease, published in the New England Journal of Medicine in 1994. This study monitored patients in the U.S. between 1978 and 1988, and estimated the median life expectancy of women with sickle cell anemia to 48 years and men 42 years. However, it authors noted that 50 percent of deaths were seen in patients ages 45 or older.
Another study, conducted between 1979 and 2005 in the U.S, estimated the average life expectancy for a woman with sickle cell anemia to be 42 years, and 38 years for a man. The results were published in Public Health Reports, based on death certificates listing sickle cell anemia as the underlying or contributing cause of death.
Both studies are now somewhat dated, and it is possible for sickle cell anemia patients to live well beyond the average life expectancy, as demonstrated in a case series of four women with the disease — three in the U.S. and one in Brazil — who lived well into their eighties. This study was published in the journal Blood in 2016.
Risk factors
A recent publication aimed to determine the main risk factors associated with death in adults with sickle cell anemia, after the approval of hydroxyurea in North America and Europe. The study followed 3,257 patients at the University of North Carolina, and also included data from nine previous studies.
Researchers identified a significantly increased risk of death with each additional 10 years of age. Sickle cell patients with pulmonary hypertension, a rare disease marked by high pressure in the blood vessels of the lungs, are known to be at a higher risk of death. Other risk factors included high levels of the enzymes creatinine or NT-proBNP, which can be associated with kidney and heart failure, respectively. The study also found low levels of hemoglobin, fetal hemoglobin, and reticulocytes (new, developing red blood cells) to be risk factors.
Childhood sickle cell anemia prognosis
In previous decades, sickle cell anemia was often fatal in childhood. But with improvements in diagnosis and medical care, this is now rarely the case, especially in North America and Europe. Survival to adulthood is predicted to be as high as 99 percent in London, 97 percent in Paris, and 94 percent in the U.S. in general for children with sickle cell anemia.
The outlook
Although people with sickle cell anemia tend to have a shorter life expectancy than is seen in the general population, advances in treatments — such as the approval of hydroxyurea and Endari (L-glutamine) — have improved survival and patients’ quality of life. Potential new therapies are also being developed.
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