Life Expectancy in the U.S. for the Population with Sickle Cell Disease

By Emily Merchant posted 01-31-2021 20:19

  

David A. Swanson (dswanson@ucr.edu)                                                                                                               
Dickson Emeritus Professor, Department of Sociology, University of California Riverside and Regional Affiliate, Center for Studies in Demography and Ecology, University of Washington

Sickle cell disease is a genetically-inherited, painful, crippling, life-threatening condition affecting at many as 100,000 people in the United States. Despite the prevalence of sickle cell disease, little is known about the life expectancy of people who suffer from it.

Using mortality data generated in a population-based surveillance study of patients with sickle cell disease over the period 2004-2008, I created a life table for the study population circa 2006 and applied it to the US population. I find that a newborn with sickle cell disease circa 2006 had a life expectancy of approximately 48 years. For the total U.S. population, newborns in 2006 were expected to live to approximately 78 years, 30 years longer than a newborn with sickle cell disease. The 2006 U.S. Black population, in which nearly all those with sickle cell disease are found, was estimated to have a life expectancy at birth of 73.2 years, about 25 years longer than a newborn with sickle cell disease. It is a long way to parity for those born with sickle cell disease.

The probability of a newborn with sickle cell disease reaching age 55 in 2006 was approximately 0.35 while the probability of a newborn in the US population as a whole living to age 55 was approximately 0.92, about 2.6 times higher. The probability of a newborn in the 2006 U.S. Black population surviving to age 55 was approximately 0.86, about 2.45 times higher than a newborn with sickle cell disease. 

A 2019 study constructed life expectancy estimates for the U.S. population with sickle cell disease via cohort simulation modeling, estimating that life expectancy at birth for the U.S. population with sickle cell disease was 54 years as of 2006. In comparing my results with this study, there is a difference of approximately six years, from 48 to 54, a difference of 12.5 percent, which I discuss by first noting that the health and survival of children with sickle cell disease have improved considerably with the advent of newborn screening, penicillin prophylaxis, pneumococcal immunization, and education about disease complications. From this perspective, it may be the case that the period life expectancy estimates I generated are biased downward because they represent older cohorts that did not have the same levels of screening, treatment, and education as those who were younger. This example of “hidden heterogeneity” implies that the youngest cohorts will live longer than both of the life tables suggest. However, this may have been picked up to some extent in the cohort simulation approach, as it estimates that the SCD population has six more years of life expectancy at birth than the estimate I generated. In any case, both estimates are consistent with an observation that the average projected lifespan of affected adults (those in the older cohorts) has not improved beyond the fifth decade. As these older cohorts are replaced by the younger ones, we can expect that the projected lifespans of affected adults will improve, an achievement due to efforts such the Sickle Cell Data Collection Program, which received $1.2 million in funding in 2019. Hopefully, additional funding will continue under the Biden Administration and beyond. As Wes James and his colleagues have observed, differential mortality/life expectancy is the ultimate inequality.

Life Expectancy in the U.S. for the Population with Sickle Cell Disease

David A. Swanson (dswanson@ucr.edu)                                                                                                               Dickson Emeritus Professor, Department of Sociology, University of California Riverside and Regional Affiliate, Center for Studies in Demography and Ecology, University of Washington

Sickle cell disease is a genetically-inherited, painful, crippling, life-threatening condition affecting at many as 100,000 people in the United States. Despite the prevalence of sickle cell disease, little is known about the life expectancy of people who suffer from it.

Using mortality data generated in a population-based surveillance study of patients with sickle cell disease over the period 2004-2008, I created a life table for the study population circa 2006 and applied it to the US population. I find that a newborn with sickle cell disease circa 2006 had a life expectancy of approximately 48 years. For the total U.S. population, newborns in 2006 were expected to live to approximately 78 years, 30 years longer than a newborn with sickle cell disease. The 2006 U.S. Black population, in which nearly all those with sickle cell disease are found, was estimated to have a life expectancy at birth of 73.2 years, about 25 years longer than a newborn with sickle cell disease. It is a long way to parity for those born with sickle cell disease.

The probability of a newborn with sickle cell disease reaching age 55 in 2006 was approximately 0.35 while the probability of a newborn in the US population as a whole living to age 55 was approximately 0.92, about 2.6 times higher. The probability of a newborn in the 2006 U.S. Black population surviving to age 55 was approximately 0.86, about 2.45 times higher than a newborn with sickle cell disease. 

A 2019 study constructed life expectancy estimates for the U.S. population with sickle cell disease via cohort simulation modeling, estimating that life expectancy at birth for the U.S. population with sickle cell disease was 54 years as of 2006. In comparing my results with this study, there is a difference of approximately six years, from 48 to 54, a difference of 12.5 percent, which I discuss by first noting that the health and survival of children with sickle cell disease have improved considerably with the advent of newborn screening, penicillin prophylaxis, pneumococcal immunization, and education about disease complications. From this perspective, it may be the case that the period life expectancy estimates I generated are biased downward because they represent older cohorts that did not have the same levels of screening, treatment, and education as those who were younger. This example of “hidden heterogeneity” implies that the youngest cohorts will live longer than both of the life tables suggest. However, this may have been picked up to some extent in the cohort simulation approach, as it estimates that the SCD population has six more years of life expectancy at birth than the estimate I generated. In any case, both estimates are consistent with an observation that the average projected lifespan of affected adults (those in the older cohorts) has not improved beyond the fifth decade. As these older cohorts are replaced by the younger ones, we can expect that the projected lifespans of affected adults will improve, an achievement due to efforts such the Sickle Cell Data Collection Program, which received $1.2 million in funding in 2019. Hopefully, additional funding will continue under the Biden Administration and beyond. As Wes James and his colleagues have observed, differential mortality/life expectancy is the ultimate inequality.

Expected Years of Life Remaining by Age 2006
Expected Years of Life REmaining in 2006

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