Rollins School of Public Health, Emory University, Atlanta, GA, USA.
Biogen, Cambridge, MA, USA.
Orphanet J Rare Dis. 2017 Nov 28;12(1):175. doi: 10.1186/s13023-017-0724-z.
Spinal muscular atrophy (SMA) is a progressive, devastating disease and a leading inherited cause of infant mortality. The limited population-based literature is confined to small regional studies. Estimates of prevalence are needed to characterize the burden of SMA and to understand trends in prevalence by disease type as new treatments become available. The reported estimates of SMA genotype prevalence at birth consistently range from 8.5-10.3 per 100,000 live births, with a mid-range estimate of 9.4 per 100,000. Among infants born with an SMA genotype, it is reported that ~58% will develop SMA Type I, 29% will develop Type II, and 13% will develop Type III, respectively.
Using evidence from peer-reviewed literature for SMA birth prevalence, age at symptom onset, and SMA type-specific survival, and incorporating United States vital statistics, we constructed life tables to estimate prevalence for SMA Types I, II, and III in the United States. We estimated the number of prevalent cases in the US to be 8526, 9429, and 10,333 based on a birth prevalence of 8.5, 9.4, and 10.3, respectively (the lower, midpoint, and upper ends of the reported range). Assuming the midpoint of 9.4 and US-reported survival, the type-specific population prevalence estimates were 1610 for SMA Type I, 3944 for SMA Type II, and 3875 for SMA Type III. Evidence-based estimates of the number of people living with SMA in the United States in the published literature were previously unavailable.
In the absence of a survey or other means to directly estimate prevalence in the US population, estimates can be calculated indirectly using a life table.
脊髓性肌萎缩症（SMA）是一种进行性、破坏性疾病，是婴儿死亡的主要遗传性原因。基于人群的有限文献仅限于小范围的区域性研究。需要对患病率进行估计，以描述 SMA 的负担，并了解随着新疗法的出现，不同疾病类型的患病率趋势。据报道，SMA 基因型在活产婴儿中的患病率始终在每 10 万活产婴儿中 8.5-10.3 例之间，中值估计值为每 10 万活产婴儿中 9.4 例。据报道，出生时患有 SMA 基因型的婴儿中，约有 58%将发展为 SMA 1 型，29%将发展为 SMA 2 型，13%将发展为 SMA 3 型。
我们使用 SMA 出生患病率、症状出现年龄和 SMA 特定类型生存率的同行评审文献证据，并结合美国生命统计数据，构建生命表来估计美国 SMA 1 型、2 型和 3 型的患病率。我们估计，在美国，SMA 1 型、2 型和 3 型的流行病例数分别为 8526、9429 和 10333 例，基于 8.5、9.4 和 10.3 的出生患病率（报告范围的下限、中点和上限）。假设中点为 9.4 和美国报告的生存率，那么特定类型的人群患病率估计值分别为 SMA 1 型 1610 例、SMA 2 型 3944 例和 SMA 3 型 3875 例。在已发表的文献中，之前没有关于美国 SMA 患者人数的基于证据的估计值。
在没有调查或其他直接在美国人群中估计患病率的方法的情况下，可以使用生命表间接计算估计值。
