Department of General Practice, School of Public Health, Aarhus University, Denmark.
Int J Epidemiol. 2011 Apr;40(2):338-45. doi: 10.1093/ije/dyq185. Epub 2010 Nov 12.
Studies have consistently shown that pregnancy smoking is associated with twice the risk of hyperactivity/inattention problems in the offspring. An association of this magnitude may indicate behavioural difficulties as one of the most important health effects related to smoking during pregnancy. However, social and genetic confounders may fully or partially account for these findings.
A cohort including all singletons born in Finland from 1 January 1987 through 31 December 2001 was followed until 1 January 2006 based on linkage of national registers. Data were available for 97% (N = 868,449) of the population. We followed singleton children of smoking and non-smoking mothers until they had an International Classification of Diseases, 10th revision, diagnosis of hyperkinetic disorder (HKD) or to the end of the observation period. We used sibling-matched Cox regression analyses to control for social and genetic confounding.
We found a much smaller association between exposure to maternal smoking during pregnancy and risk of HKD in children using the sibling-matched analysis [hazards ratio (HR) = 1.20, 95% confidence interval (CI) 0.97-1.49] than was observed in the entire cohort (HR 2.01, 95% CI 1.90-2.12).
Our findings suggest that the strong association found in previous studies may be due to time-stable familial factors, such as environmental and genetic factors. If smoking is a causal factor, the effect is small and less important than what the previous studies indicate.
研究一致表明，孕期吸烟会使后代出现多动/注意力不集中问题的风险增加一倍。如此大的关联可能表明行为困难是与孕期吸烟相关的最重要健康影响之一。然而，社会和遗传混杂因素可能完全或部分解释这些发现。
一项队列研究纳入了 1987 年 1 月 1 日至 2001 年 12 月 31 日期间在芬兰出生的所有单胎，通过国家登记册的链接，随访至 2006 年 1 月 1 日。人群中 97%（N=868449）的数据可用。我们随访了吸烟和不吸烟母亲的单胎子女，直至他们被诊断为多动障碍（HKD）或观察期结束。我们使用同胞匹配 Cox 回归分析来控制社会和遗传混杂。
我们发现，使用同胞匹配分析，孕期暴露于母亲吸烟与儿童多动障碍风险之间的关联要小得多[风险比（HR）=1.20，95%置信区间（CI）0.97-1.49]，而在整个队列中观察到的关联更大（HR 2.01，95% CI 1.90-2.12）。
我们的研究结果表明，以前研究中发现的强关联可能是由于稳定的家族因素，如环境和遗传因素所致。如果吸烟是一个因果因素，那么其影响很小，不如以前的研究表明的那么重要。
