Congenital and Developmental Disorders
Another component of the burden of noncommunicable disease comes from congenital and developmental disorders.4 As low- and middle-income countries make progress in controlling the major childhood illnesses, a number of congenital and developmental disorders are likely to be revealed.
In Africa, 2 percent of infants have sickle cell disease, one of the inherited conditions, or hemoglobinopathies, that affects the normal functioning of hemoglobin in the red blood cells (figure 5.1). The condition is largely absent among adolescents and adults because of the high mortality rates among children. As countries control malaria and improve the diagnosis and treatment of infections with antibiotics, more infants with this condition will survive into adulthood.
[Figure
5.1]
"In Africa, 2 percent of infants have sickle cell disease . . ."
The prevalence of learning and developmental disabilities (functional limitations that result from damage to the nervous system) is at least 10 to 20 percent in high-income countries. Infants and children with these disabilities are less likely to survive and come to the attention of the health system until countries are better able to control common infectious diseases and the coverage of their health systems becomes more complete.
Congenital and developmental disorders arise from a variety of conditions. Many of these disorders are strictly genetic: sickle cell anemia occurs in one out of four children whose parents carry the recessive gene for this condition, and Down syndrome is caused by the presence of a third chromosome. Other disorders arise when fetal development is harmed, as occurs with fetal alcohol syndrome, iodine deficiency, and congenital rubella. A third class of disorders arises from adverse environmental exposure, for example, neurological damage caused by cerebral malaria, bacterial meningitis, or lead poisoning.
". . . 7 percent of the world's population carries genes that can cause hemoglobin disorders, and each year between 300,000 and 500,000 babies are born with severe forms of these disorders. Mild mental retardation from lead ingestion accounts for 1 percent of the global disease burden . . ."
These disorders account for a significant share of the world's disease burden. Some 7 percent of the world's population carries genes that can cause hemoglobin disorders, and each year between 300,000 and 500,000 babies are born with severe forms of these disorders. Mild mental retardation from lead ingestion accounts for 1 percent of the global disease burden, about 9.8 million DALYs, and lead ingestion is only one of many causes of mental retardation.
The consequences of these disorders vary widely and depend both on the severity of the condition and on the context. When a health system can assure proper diagnosis and penicillin prophylaxis, many children can live normal lives despite carrying sickle cell. Hyperactivity disorders and dyslexia are problematic in school settings that do not have resources to address them. Stigmatization may prevent individuals from participating in social activities even when their functional limitations are not a constraint. In places where public policy promotes the construction of ramps for wheel chairs or Braille signs, functional limitations are less restrictive.
Some health interventions address congenital and developmental disorders by preventing them. These include measures like offering genetic screening and counseling for couples when serious congenital disorders are detected, vaccinating against Hib and meningitis to avert neurological damage, implementing behavioral interventions to stop alcohol use during pregnancy to avert fetal alcohol syndrome, eliminating environmental exposure to toxins such as lead that cause mental retardation, and redressing nutritional deficiencies among pregnant women.
Other interventions are available to prevent disorders from progressing to disability:
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Screening for metabolic disorders identifies individuals who will develop neurological damage after ingesting certain foods. Children at risk for such disorders and their parents can be counseled to restrict the identified children's diets accordingly.
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Screening for sickle cell anemia can be followed by penicillin prophylaxis to reduce the risk of death and morbidity from infections.
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Screening and treatment for congenital hypothyroidism can avert developmental damage that results in severe cognitive disabilities.
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Prompt treatment for cerebral malaria can avert long-term neurological damage.
When disorders cannot be prevented, in some cases treatments are available to mitigate their impact on an individual's health. People with conditions caused by severe thalassemias, genetic disorders involving defective hemoglobin production in the blood, may require blood transfusions with washed red blood cells adequately screened for blood-borne diseases; individuals with sickle cell disease can be hospitalized and treated with analgesics when they develop severe bone pain; and nutritional fortification, surgery, rehabilitation, or special education may be able to reduce the severity of impairments.
Finally, when disorders cannot be prevented or treated, mitigating the impact of the disability on a person's quality of life might be possible. Many interventions are directed at associated health conditions; for example, people born with Down syndrome are likely to require treatment or therapy for poor hearing and vision, congenital heart defects, and low mental capacities. Other interventions address environmental constraints on an individual's participation in family and social life, whether by improving physical mobility through appropriate investments in public infrastructure, such as wheelchair accessible mass transit, buildings, and restrooms; building social support networks; or addressing social stigma and educating the public to be more inclusive of people with disabilities.
". . . many interventions for addressing congenital and developmental disorders are cost-effective."
DCP2 finds that many interventions for addressing congenital and developmental disorders are cost-effective. Chapter 34 highlights penicillin prophylaxis for newborns with sickle cell anemia, which costs between US$7,000 and US$12,000 per death averted and US$250 to US$600 per DALY averted. It also notes that screening for sickle cell anemia among people of African descent costs about US$6,700 per death averted, but that universal screening in other populations with low prevalence is not cost-effective. Chapter 49 finds that folic acid fortification of grains to prevent birth defects is cost-effective, costing an average of US$36 per DALY averted in Latin America and the Caribbean, US$40 per DALY averted in Sub-Saharan Africa, US$58 per DALY averted in South Asia, and US$160 per DALY averted in East Asia and the Pacific. Prenatal screening and selective pregnancy termination to prevent Down syndrome, spina bifida, and other frequently fatal congenital disorders can be highly cost-effective, but raise ethical, social, and cultural concerns that have to be addressed in ways that respect the gravity of such decisions and assure the protection of human rights.
"Better nourishment for pregnant women . . . not only would be beneficial to women's own health and reduce the risk of maternal mortality, but would also reduce the chances of their children being born with a congenital disorder."
In addressing congenital and developmental disorders, the evidence in DCP2 demonstrates the strong relationships between diseases. Immunization programs aimed at preventing rubella reduce the likelihood of congenital deformities in newborns, and better control of malaria would reduce the prevalence of neurological disorders resulting from cerebral malaria. Better nourishment for pregnant women, with particular attention to micronutrients such as vitamin A, folic acid, and iodine, not only would be beneficial to women's own health and reduce the risk of maternal mortality, but would also reduce the chances of their children being born with a congenital disorder.
