Predictors of attendance and dropout at the Lung Health Study 11-year follow-up

Participant attrition and attendance at follow-up were examined in a multicenter, randomized, clinical trial. The Lung Health Study (LHS) enrolled a total of 5887 adults to examine the impact of smoking cessation coupled with the use of an inhaled bronchodilator on chronic obstructive pulmonary disease (COPD). Of the initial LHS 1 volunteers still living at the time of enrolment in LHS 3 (5332), 4457 (84%) attended the LHS 3 clinic visit, a follow-up session to determine current smoking status and lung function. The average period between the beginning of LHS 1 and baseline interview for LHS 3 was 11 years. In univariate analyses, attenders were older, more likely female, more likely to be married, smoked fewer cigarettes per day, and were more likely to have children who smoked at the start of LHS 1 than non-attenders. Attenders were also less likely to experience respiratory symptoms, such as cough, but had decreased baseline lung function compared with non-attenders. Volunteers recruited via mass mailing were more likely to attend the long-term follow-up visit. Those recruited by public site, worksite, or referral methods were less likely to attend. In multivariate models, age, gender, cigarettes smoked per day, married status, and whether participants' children smoked were identified as significant predictors of attendance versus non-attendance at LHS 3 using stepwise logistic regression. Treatment condition (smoking intervention or usual care) was not a significant predictor of attendance at LHS 3. Older females who smoked less heavily were most likely to participate. These findings may be applied to improve participant recruitment and retention in future clinical trials.