Lee Peter N
P.N.Lee Statistics and Computing Ltd, 17 Cedar Road, Sutton, Surrey, SM2 5DA, UK.
Harm Reduct J. 2015 Mar 20;12:8. doi: 10.1186/s12954-015-0040-7.
The "gateway hypothesis" usually refers to the possibility that the taking up of habit A, which is considered harmless (or less harmful), may lead to the subsequent taking up of another habit, B, which is considered harmful (or more harmful).
Possible approaches to designing and analysing studies to test the hypothesis are discussed. Evidence relating to the use of snus (A) as a gateway for smoking (B) is then evaluated in detail.
RESULTS-DESIGN AND ANALYSIS CONSIDERATIONS: The importance of having appropriate data available on the sequence of use of A and B and on other potential confounding factors that may lead to the taking up of B is emphasised. Where randomised trials are impractical, the preferred designs include the prospective cohort study in which ever use of A and of B is recorded at regular intervals, and the cross-sectional survey in which time of starting to use A and B is recorded. Both approaches allow time-stratified analytical methods to be used, in which, in each time period, risk of initiating B among never users of B at the start of the interval is compared according to prior use of A. Adjustment in analysis for the potential confounding factors is essential.
RESULTS-REVIEW OF EVIDENCE: Of 11 studies of possible relevance conducted in Sweden, Finland or Norway, only one seriously addresses potential confounding by those other factors involved in the initiation of smoking. Furthermore, 5 of the 11 studies are of a design that does not allow proper testing of the gateway hypothesis for various reasons, and the analysis is unsatisfactory, sometimes seriously, in all the remaining six.
While better analyses could be attempted for some of the six studies identified as having appropriate design, the issues of confounding remain, and more studies are clearly needed. To obtain a rapid answer, a properly designed cross-sectional survey is recommended.
“通路假说”通常指的是，养成被认为无害（或危害较小）的习惯A，可能会导致随后养成另一种被认为有害（或危害更大）的习惯B。
讨论了设计和分析用于检验该假说的研究的可能方法。然后详细评估了有关使用口含烟（A）作为吸烟（B）通路的证据。
结果——设计与分析考量：强调了获取关于A和B使用顺序以及可能导致养成B习惯的其他潜在混杂因素的适当数据的重要性。在随机试验不切实际的情况下，首选设计包括前瞻性队列研究，即定期记录A和B的使用情况，以及横断面调查，即记录开始使用A和B的时间。这两种方法都允许使用时间分层分析方法，即在每个时间段内，根据之前对A的使用情况，比较在该时间段开始时从未使用过B的人群中开始使用B的风险。在分析中对潜在混杂因素进行调整至关重要。
结果——证据综述：在瑞典、芬兰或挪威进行的11项可能相关的研究中，只有一项认真探讨了吸烟起始过程中其他因素造成的潜在混杂问题。此外，11项研究中有5项由于各种原因采用了无法对通路假说进行适当检验的设计，在其余6项研究中，分析结果均不尽人意，有时甚至严重不足。
虽然对于确定设计合理的6项研究中的部分研究可以尝试进行更好的分析，但混杂问题依然存在，显然还需要更多研究。为了快速得出答案，建议进行精心设计的横断面调查。
