Safe Transportation Research & Education Center, Department of Environmental Health Sciences, University of California, Berkeley, California 94720-7374, USA.
Inj Prev. 2010 Dec;16(6):372-5. doi: 10.1136/ip.2010.027607. Epub 2010 Jun 29.
To determine whether either the inclusion of adults in matched cohort studies of passenger vehicle occupants or modification of age effects by collision severity biases child restraint risk ratios biases estimate of child restraint effectiveness.
Monte Carlo data simulations were conducted to represent 10,000 collision-involved vehicles carrying a mix of children and adults. The effects of age category, adult seat belt use, child seat belt use, and child safety seat use were set to known values. Age was a modifier of the adult and child seat belt risk ratios and of the safety seat RR, and crash severity was a modifier of the age RRs. We also created an association between restraint use and collision severity to confound the restraint-death risk associations. RRs were estimated using conditional Poisson regression and compared with the true values.
Estimated RRs for death were identical to the simulated values. The average child safety seat RR was 0.42 (true value 0.42), and the average seat belt RRs for children were 0.54 (true value 0.54) for those aged 0-3 years and 0.61 (true value 0.61) for those aged 4-17. Age effects were also correctly estimated, 1.69 (true value 1.69) for those aged 0-3 and 1.35 (true value 1.35) for those aged 4-17.
Neither the use of matched sets of adults and children nor the modification of age effects by collision severity biases estimates of child restraint effectiveness in matched cohort studies.
确定在涉及乘用车乘客的匹配队列研究中纳入成年人，或通过碰撞严重程度修改年龄效应，是否会偏倚儿童约束装置风险比，从而偏倚儿童约束装置效果的估计值。
进行了蒙特卡罗数据模拟，以代表 10000 辆涉及儿童和成年人的碰撞车辆。年龄类别、成人安全带使用、儿童安全带使用和儿童安全座椅使用的效果设置为已知值。年龄是成人和儿童安全带风险比以及安全座椅 RR 的修饰符，碰撞严重程度是年龄 RR 的修饰符。我们还创建了约束使用与碰撞严重程度之间的关联，以混淆约束死亡风险关联。使用条件泊松回归估计 RR，并与模拟值进行比较。
死亡的估计 RR 与模拟值相同。儿童安全座椅的平均 RR 为 0.42（真实值 0.42），0-3 岁儿童的平均安全带 RR 为 0.54（真实值 0.54），4-17 岁儿童的平均安全带 RR 为 0.61（真实值 0.61）。年龄效应也得到了正确估计，0-3 岁的 RR 为 1.69（真实值 1.69），4-17 岁的 RR 为 1.35（真实值 1.35）。
在匹配队列研究中，既不使用成人和儿童的匹配组，也不通过碰撞严重程度修改年龄效应，会偏倚儿童约束装置效果的估计值。
