Department of Social Research, Faculty of Social Sciences, University of Helsinki, P.O. Box 18, 00014, Helsinki, Finland.
Center for Twin Research, Osaka University Graduate School of Medicine, Osaka, Japan.
Sci Rep. 2022 Jul 31;12(1):13148. doi: 10.1038/s41598-022-17536-x.
We tested the causality between education and smoking using the natural experiment of discordant twin pairs allowing to optimally control for background genetic and childhood social factors. Data from 18 cohorts including 10,527 monozygotic (MZ) and same-sex dizygotic (DZ) twin pairs discordant for education and smoking were analyzed by linear fixed effects regression models. Within twin pairs, education levels were lower among the currently smoking than among the never smoking co-twins and this education difference was larger within DZ than MZ pairs. Similarly, education levels were higher among former smoking than among currently smoking co-twins, and this difference was larger within DZ pairs. Our results support the hypothesis of a causal effect of education on both current smoking status and smoking cessation. However, the even greater intra-pair differences within DZ pairs, who share only 50% of their segregating genes, provide evidence that shared genetic factors also contribute to these associations.
我们利用不一致的双胞胎对这一自然实验，检验了教育和吸烟之间的因果关系，从而能够最优地控制背景遗传和儿童期社会因素。通过线性固定效应回归模型，对来自 18 个队列的 10527 对同卵（MZ）和异卵（DZ）双胞胎的教育和吸烟不一致数据进行了分析。在双胞胎中，目前吸烟的双胞胎的教育水平低于从不吸烟的双胞胎，而这种教育差异在 DZ 双胞胎中比 MZ 双胞胎中更大。同样，曾经吸烟的双胞胎的教育水平高于当前吸烟的双胞胎，而且这种差异在 DZ 双胞胎中更大。我们的结果支持教育对当前吸烟状况和戒烟都有因果影响的假设。然而，DZ 双胞胎之间的个体内差异更大，他们仅共享 50%的可分离基因，这为共同遗传因素也促成这些关联提供了证据。
