elements would have been under the control of the researchers. Those characteristics are summarized in Table 7-1. The table includes a description of the characteristics of studies and some of the ideals and challenges related to them. Researchers must weigh the benefits of those ideals across all the characteristics because a study that meets all the ideals typically will not be feasible to conduct. For example, it would be difficult to conduct a study with a large sample that requires autopsies for all cases. Furthermore, journals often have page limitations that preclude the publication of detailed analyses, such as sensitivity analyses, which ideally would be included in studies like those discussed here.

Although the 11 studies discussed here are observational studies and have limitations inherent to observational studies, it is important that the studies took advantage of natural experiments to directly evaluate the effects of an intervention (a smoking ban and concomitant activities) on a health outcome of interest (acute coronary events). As discussed in Assessing the Health Impact of Air Quality Regulations: Concepts and Methods

TABLE 7-1 Characteristics and Challenges in Study Designa



Research Challenges to Consider

Study population

  • Stable population

  • Active surveillance

  • Large sample

  • Adequate baseline data on secondhand-smoke exposure

  • Individual-level data (such as, smoking status, secondhand-smoke exposure, preexisting risk factors)

When using “natural” intervention, such as smoking ban, it is difficult to control many aspects of population

  • Population cannot be held constant, because of immigration and emigration

  • Active surveillance is sometimes possible but would increase costs

  • Sample size is limited by population covered by smoking ban

  • If prospective, an observational study can have baseline and individual-level data on secondhand-smoke exposure and risk factors, but is much more expensive to conduct and requires more complex human-subjects use approval

  • Hospital records are not always a reliable source of data on smoking status

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