Mann Vera, De Stavola Bianca L, Leon David A
Medical Statistics Unit, Department of Epidemiology and Population Health, London School of Hygiene and Tropical Medicine, UK.
Stat Med. 2004 Sep 15;23(17):2745-56. doi: 10.1002/sim.1853.
In epidemiology the analyses of family or twin studies do not always fully exploit the data, as information on differences between siblings is often used while between-families effect are not considered. We show how cross-sectional time-series linear regression analysis can be easily implemented to estimate within- and between-families effects simultaneously and how these effects can then be compared using the Hausman test. We illustrate this approach with data from the Uppsala family study on blood pressure in children with age ranging from 5.5 to 12.3 years for the younger and from 7.5 to 13.8 years for the older siblings. Comparing the effect of differences in birth weight on blood pressure within-family (in full siblings) and between-families (in unrelated children) allows us to study the contributions of fixed and pregnancy-specific maternal effects on birth weight and consequently on blood pressure. Our data showed a 0.88 mmHg decrease (95 per cent confidence interval: -1.7 to -0.03 mmHg) in systolic blood pressure for one standard deviation increase in birth weight between siblings within a family and 0.88 mmHg (95 per cent confidence interval: -1.6 to -0.2 mmHg) decrease in systolic blood pressure for one standard deviation increase in birth weight between unrelated children. These estimates were controlled for sex, age, pubertal stage, body size and pulse rate of the children at examination and for maternal body size and systolic blood pressure. The within- and between-families effects were not significantly different, p = 0.19, suggesting that fixed and pregnancy-specific factors have similar effects on childhood systolic blood pressure.
在流行病学中，家庭或双胞胎研究的分析并不总是能充分利用数据，因为通常只使用了兄弟姐妹之间差异的信息，而未考虑家庭间效应。我们展示了如何轻松实施横断面时间序列线性回归分析，以同时估计家庭内和家庭间效应，以及如何随后使用豪斯曼检验比较这些效应。我们用来自乌普萨拉家庭研究的数据来说明这种方法，该研究针对年龄在5.5至12.3岁（较年幼的兄弟姐妹）和7.5至13.8岁（较年长的兄弟姐妹）的儿童进行血压研究。比较出生体重差异对家庭内（亲兄弟姐妹）和家庭间（无血缘关系的儿童）血压的影响，使我们能够研究固定因素和特定孕期母体因素对出生体重进而对血压的贡献。我们的数据显示，在一个家庭中，兄弟姐妹间出生体重每增加一个标准差，收缩压下降0.88 mmHg（95%置信区间：-1.7至-0.03 mmHg）；在无血缘关系的儿童中，出生体重每增加一个标准差，收缩压下降0.88 mmHg（95%置信区间：-1.6至-0.2 mmHg）。这些估计值已对儿童检查时的性别、年龄、青春期阶段、体型和脉搏率以及母体体型和收缩压进行了控制。家庭内和家庭间效应无显著差异，p = 0.19，这表明固定因素和特定孕期因素对儿童收缩压的影响相似。
