Odierna Donna H, Schmidt Laura A
University of California, Berkeley, USA.
Am J Public Health. 2009 Aug;99(8):1515-21. doi: 10.2105/AJPH.2007.111138. Epub 2008 Nov 13.
We sought to determine whether failure to locate hard-to-reach respondents in longitudinal studies causes biased and inaccurate study results.
We performed a nonresponse simulation in a survey of 498 low-income women who received cash aid in a California county. Our simulation was based on a previously published analysis that found that women without children who applied for General Assistance experienced more violence than did women with children who applied for Temporary Assistance to Needy Families. We compared hard-to-reach respondents whom we reinterviewed only after extended follow-up effort 12 months after baseline with other respondents. We then removed these hard-to-reach respondents from our analysis.
Other than having a greater prevalence of substance dependence (14% vs 6%), there were no significant differences between hard- and easy-to-reach respondents. However, excluding the hard to reach would have decreased response rates from 89% to 71% and nullified the findings, a result that did not stem primarily from reduced statistical power.
The effects of failure to retain hard-to-reach respondents are not predicable based on respondent characteristics. Retention of these respondents should be a priority in public health research.
我们试图确定在纵向研究中未能找到难以接触到的受访者是否会导致有偏差且不准确的研究结果。
我们对加利福尼亚州一个县498名领取现金援助的低收入女性进行了一项无应答模拟调查。我们的模拟基于之前发表的一项分析，该分析发现申请一般援助的无子女女性比申请贫困家庭临时援助的有子女女性遭受更多暴力。我们将仅在基线后12个月经过长时间随访努力才重新访谈的难以接触到的受访者与其他受访者进行了比较。然后我们在分析中剔除了这些难以接触到的受访者。
除了药物依赖患病率更高（14%对6%）外，难以接触到的受访者与容易接触到的受访者之间没有显著差异。然而，排除难以接触到的受访者会使应答率从89%降至71%，并使研究结果无效，这一结果并非主要源于统计效力的降低。
基于受访者特征无法预测未能留住难以接触到的受访者的影响。在公共卫生研究中，留住这些受访者应是优先事项。
