Sickle cell disease (SCD) is a lifelong and costly chronic disease characterized by hemolytic anemia, pain crisis, and multi-end organ damage. Published estimates of SCD prevalence in the United States (US) range from approximately 85,000 to 100,000 people, most of whom are African American or Hispanic American. Individuals with SCD on average live two to three decades less than the general US population (Piel et al 2017). They also have markedly impaired patient-reported health-related quality-of-life (HRQOL) due in part to fatigue, pain, and impaired physical functioning, which leads to a significant reduction in work productivity. However, there are limited data available on the societal costs of SCD, such as lost lifetime earnings, which may lead to an underestimate of the true impact of this disease in a vulnerable population.
We developed a simulation model to estimate the differences in life expectancy measured in years, quality-adjusted life-years (QALY) and income lost due to reduced life expectancy. Results were compared between a population of patients born with SCD in the US and a sex- and race-matched US population born without SCD and to the general US population.
To build the model, we (1) generated a Poisson regression from published birth and mortality estimates for SCD supplemented with data from the Centers for Disease Control (CDC) Multiple Cause of Death database to create age-specific life tables for a population of individuals with SCD (SCD population); (2) used published life tables from the CDC to develop age-specific death rates for a population without SCD (non-SCD population); (3) incorporated published utility weights for SCD adolescents and adults, and for the US general population to estimate the impact of the disease on HRQOL; (4) used US Bureau of Labor Statistics Supplemental Survey of Annual Personal Income data to calculate the expected annual personal income based on age, race, and gender; (5) built a cohort simulation model using R (version 3.4.2) to estimate the life expectancy, QALYs, and lost income for the SCD population compared to the non-SCD population, and the US general population. All analyses used Monte Carlo sampling to characterize uncertainty.
We estimated that there would be 1,950 newborns with SCD born in the US annually. The projected life expectancy at birth is 54 years for the SCD population compared with 76 years for the age- and race-matched non-SCD population and 79 years for the general US population. Moreover, the quality-adjusted life expectancy of the SCD population (33 years) is less than half that of the matched non-SCD population (67 years) and general US population (69 years). Projected lifetime income for an individual in the SCD population is approximately $1.2 million compared with $1.9 million for an individual in the matched non-SCD population and $2.0 million in the general US population (Figure). Therefore, our model estimates that each individual with SCD loses over $700,000 in lifetime income due to early mortality associated with SCD.
A contemporary simulated cohort of individuals born with SCD is projected to live 22 years less than a matched population of individuals without SCD. Moreover, when adjusted for diminished HRQOL, our model suggests that patients living with SCD lose over three decades in life expectancy compared to a matched non-SCD population. Given the 22-year difference in life expectancy results in approximately $700,000 in lost lifetime income for each person born with SCD, a contemporary SCD birth cohort of 1,950 individuals would lose over $1.4 billion in lifetime income due to premature mortality. These losses are a conservative estimate since they do not include any direct medical costs or other societal costs such as lost educational potential, lost workdays due to caregivers caring for their affected children, or patient time spent in the hospital or visiting the emergency department; nor do they account for additional challenges in finding and maintaining active employment that have been previously described as substantial among individuals with SCD. In conclusion, SCD has devastating societal consequences beyond the resources required to provide medical care for patients underscoring the urgent need to develop disease-modifying therapies that can improve the underlying morbidity and mortality of individuals living with SCD.
Agodoa:Global Blood Therapeutics: Employment. Lubeck:Global Blood Therapeutics: Research Funding. Danese:Global Blood Therapeutics: Consultancy, Research Funding. Pappu:Global Blood Therapeutics: Employment. Howard:Global Blood Therapeutics: Employment. Gleeson:Global Blood Therapeutics: Consultancy, Research Funding. Halperin:Global Blood Therapeutics: Consultancy, Research Funding. Lanzkron:PCORI: Research Funding; NHLBI: Research Funding; GBT: Research Funding; selexys: Research Funding; Ironwood: Research Funding; Pfizer: Research Funding; Prolong: Research Funding; HRSA: Research Funding.
Asterisk with author names denotes non-ASH members.