Department of Epidemiology, Columbia University, New York, NY, USA.
Int J Epidemiol. 2012 Apr;41(2):495-503. doi: 10.1093/ije/dyr193. Epub 2011 Dec 7.
The incidence and prevalence of autism have dramatically increased over the last 20 years. Decomposition of autism incidence rates into age, period and cohort effects disentangle underlying domains of causal factors linked to time trends. We estimate an age-period-cohort effect model for autism diagnostic incidence overall and by level of functioning.
Data are drawn from sequential cohorts of all 6 501 262 individuals born in California from 1992 to 2003. Autism diagnoses from 1994 to 2005 were ascertained from the California Department of Development Services Client Development and Evaluation Report.
Compared with those born in 1992, each successively younger cohort has significantly higher odds of an autism diagnosis than the previous cohort, controlling for age and period effects. For example, individuals born in 2003 have 16.6 times the odds of an autism diagnosis compared with those born in 1992 [95% confidence interval (CI) 7.8-35.3]. The cohort effect observed in these data is stronger for high than for low-functioning children with an autism diagnosis.
Autism incidence in California exhibits a robust and linear positive cohort effect that is stronger among high-functioning children with an autism diagnosis. This finding indicates that the primary drivers of the increases in autism diagnoses must be factors that: (i) have increased linearly year-to-year; (ii) aggregate in birth cohorts; and (iii) are stronger among children with higher levels of functioning.
自闭症的发病率和患病率在过去 20 年中急剧上升。将自闭症发病率分解为年龄、时期和队列效应，可以厘清与时间趋势相关的因果因素的潜在领域。我们对自闭症整体诊断发病率以及不同功能水平的发病率进行了年龄-时期-队列效应模型的估计。
数据来自加利福尼亚州从 1992 年到 2003 年连续出生的所有 6501262 个人的队列。1994 年至 2005 年的自闭症诊断是从加利福尼亚州发展服务部客户发展和评估报告中获得的。
与 1992 年出生的人相比，每一个较年轻的队列在控制年龄和时期效应的情况下，自闭症诊断的几率都显著增加。例如，与 1992 年出生的人相比，2003 年出生的人患自闭症的几率高出 16.6 倍（95%置信区间 7.8-35.3）。在这些数据中，高功能自闭症儿童的队列效应比低功能自闭症儿童的队列效应更强。
加利福尼亚州的自闭症发病率呈现出显著且线性的正队列效应，而高功能自闭症儿童的这种效应更强。这一发现表明，自闭症诊断增加的主要驱动因素必须是：（i）逐年线性增加；（ii）在出生队列中聚集；（iii）在功能水平较高的儿童中更强。
