Lamson S H, Hook E B
Am J Hum Genet. 1980 Sep;32(5):743-53.
The familial increase in the rate of Down syndrome with maternal age can be represented by a simple equation, consisting of the sum of a constant term plus an exponential term that is a first-order function of masternal age: y = a + exp (b + cx), where y is the rate in live births, x is maternal age, and a, b, and c are constants. Unlikely analyses in which two separate equations were derived from different segments of the 20 to 49 maternal age range, this single, simple equation can be applied to the entire range. An unlike previous complex equations that were derived by regression analysis for the entire age range, the component terms can be readily understood as contributions by different etiologic categories. This model fits the data recently available by 1-year intervals about as well as the approach that used separate equations, but it has fewer parameters and requires no ad hoc division of the age range. However, it does not postulate a sharp transition in biological processes around maternal age 30, but, rather, a process continuously accumulating at a constant exponential rate (analogous to that produced by an infectious mechanism), superimposed upon a constant background rate.
唐氏综合征发病率随母亲年龄增长而呈现的家族性增加可以用一个简单方程来表示，该方程由一个常数项加上一个指数项组成，指数项是母亲年龄的一阶函数：y = a + exp (b + cx)，其中y是活产儿中的发病率，x是母亲年龄，a、b和c是常数。与从20至49岁母亲年龄范围的不同部分得出两个单独方程的分析不同，这个单一的简单方程可应用于整个范围。与之前通过对整个年龄范围进行回归分析得出的复杂方程不同，其组成项可以很容易地理解为不同病因类别的贡献。该模型对最近按1年间隔提供的数据的拟合程度与使用单独方程的方法相当，但它的参数更少，且不需要对年龄范围进行特殊划分。然而，它并未假定在母亲年龄30岁左右生物过程会发生急剧转变，而是假定在一个恒定的背景率之上，存在一个以恒定指数率持续累积的过程（类似于由感染机制产生的过程）。
