Veldhuizen Scott, Adair Carol E, Methot Christian, Kopp Brianna C, O'Campo Patricia, Bourque Jimmy, Streiner David L, Goering Paula N
Social and Epidemiological Research Department, Centre for Addiction and Mental Health, 33 Russell St, Toronto, ON, M5S 2S1, Canada,
Soc Psychiatry Psychiatr Epidemiol. 2015 Feb;50(2):195-202. doi: 10.1007/s00127-014-0909-x. Epub 2014 Jun 12.
Participant retention is an important challenge in longitudinal research on homeless people. High attrition can threaten validity, and may represent lost opportunities to deliver interventions. In this article, we report on attrition in the At Home/Chez Soi study, a multi-site randomized controlled trial of a housing intervention for homeless people with mental illness.
We first calculate life tables, and then use clustered logistic regression to implement a discrete-time survival model. We use splines and indicator variables to capture non-linear and group-specific variation over time in the hazard function. As potential predictors, we consider study group, site, date of recruitment, age, sex, baseline substance dependence, baseline psychotic disorder, time homeless in life, community functioning, and education.
The study recruited 2,148 homeless people with mental illness. Of these, 1,158 were randomized to the housing first intervention (HF), and 990 to treatment as usual (TAU). Excluding 79 people known to have died, attrition was 14%. This proportion was higher in TAU than in HF (21 vs. 8%, p < 0.01). Attrition was significantly lower in one site than elsewhere, and was also lower among those with substance dependence (13 vs. 18%, p < 0.01) and among those enrolled earlier in the study. The hazard varied over time in complex ways.
Results imply that study factors are more important than participant characteristics as determinants of retention, and that the immediate period after randomization is a crucial one. The high overall retention demonstrates the effectiveness of existing techniques for retaining participants.
在针对无家可归者的纵向研究中，参与者保留是一项重要挑战。高损耗率可能会威胁到研究的有效性，并且可能意味着失去提供干预措施的机会。在本文中，我们报告了“在家/chez Soi”研究中的损耗情况，该研究是一项针对患有精神疾病的无家可归者的住房干预措施的多地点随机对照试验。
我们首先计算生命表，然后使用聚类逻辑回归来实施离散时间生存模型。我们使用样条函数和指示变量来捕捉危险函数随时间的非线性和特定组变化。作为潜在预测因素，我们考虑研究组、地点、招募日期、年龄、性别、基线物质依赖、基线精神障碍、一生中无家可归的时间、社区功能和教育程度。
该研究招募了2148名患有精神疾病的无家可归者。其中，1158人被随机分配到先住房干预组（HF），990人被分配到常规治疗组（TAU）。排除已知死亡的79人后，损耗率为14%。TAU组的这一比例高于HF组（21%对8%，p<0.01）。一个地点的损耗率明显低于其他地点，在有物质依赖的人群中损耗率也较低（13%对18%，p<0.01），并且在研究早期招募的人群中损耗率也较低。危险随时间以复杂的方式变化。
结果表明，作为保留率的决定因素，研究因素比参与者特征更重要，并且随机分组后的 immediately 时期是关键时期。较高的总体保留率证明了现有参与者保留技术的有效性。
