From 1995 to 1998, the U.S. SIDS rate for births at 37–39 weeks of gestation was 0.73/1000, while the SIDS rate for births at 28–31 weeks of gestation was 2.39/1000.Anemia has also been linked to SIDS (however, per item 6 in the list of epidemiologic characteristics below, extent of anemia cannot be evaluated at autopsy because an infants total hemoglobin can only be measured during life). SIDS incidence rises from zero at birth, is highest from two to four months of age, and declines toward zero after the infants first year. Genetics
Genetics plays a role, as SIDS is more prevalent in males. There is a consistent 50% male excess in SIDS per 1000 live births of each sex. Given a 5% male excess birth rate, there appears to be 3.15 male SIDS cases per 2 female cases, for a male fraction of 0.61. This value of 61% in the US is an average of 57% black male SIDS, 62.2% white male SIDS and 59.4% for all other races combined. Note that when multiracial parentage is involved, infant race is arbitrarily assigned to one category or the other; most often it is chosen by the mother. The X-linkage hypothesis for SIDS and the male excess in infant mortality have shown that the 50% male excess might be related to a dominant X-linked allele, occurring with a frequency of 1⁄3 that is protective against transient cerebral anoxia. An unprotected male would occur with a frequency of 2⁄3 and an unprotected female would occur with a frequency of 4⁄9.
Causes
Dietary exposure to aristolochic acid is the cause of BEN and its attendant transitional cell cancers. Former hypotheses that included roles for ochratoxin, poisoning by organic compounds leached from lignite or by heavy metals, viruses, and trace-element deficiencies, are not supported by current evidence. Genetic factors may be involved in determining which persons exposed to aristolochic acid suffer from BEN and which do not.In the Balkan region, dietary aristolochic acid exposure may come from the consumption of the seeds of Aristolochia clematitis (European birthwort), a plant native to the endemic region, which grows among wheat plants and whose seeds mingle with the wheat used for bread. Aristolochic-acid-containing herbal remedies used in traditional Chinese medicine are associated with a related—possibly identical—condition known as "Chinese herbs nephropathy".Exposure to aristolochic acid is associated with a high incidence of uroepithelial tumorigenesis. Diagnosis
History
The first official published description of the disease was made by the Bulgarian nephrologist Dr.Yoto Tanchev (1917–2000) and his team in 1956 in the Bulgarian Journal Savremenna Medizina, a priority generally acknowledged by the international nephrological community. Their study was based on a wide screening of inhabitants of the villages around the town of Vratsa, Bulgaria.