ABSTRACT: BACKGROUND:To evaluate participant-related variables associated with missing assessment(s) at follow-up visits during a longitudinal research study. METHODS:This is a prospective, longitudinal, multi-site study of 196 acute respiratory distress syndrome (ARDS) survivors. More than 30 relevant sociodemographic, physical status, and mental health variables (representing participant characteristics prior to ARDS, at hospital discharge, and at the immediately preceding follow-up visit) were evaluated for association with missed assessments at 3, 6, 12, and 24-month follow-up visits (89-95% retention rates), using binomial logistic regression. RESULTS:Most participants were male (56%), white (58%), and???high school education (64%). Sociodemographic characteristics were not associated with missed assessments at the initial 3-month visit or subsequent visits. The number of dependencies in Activities of Daily Living (ADLs) at hospital discharge was associated with higher odds of missed assessments at the initial visit (OR: 1.26, 95% CI: 1.12, 1.43). At subsequent 6-, 12-, and 24 months visits, post-hospital discharge physical and psychological status were not associated with subsequent missed assessments. Instead, the following were associated with lower odds of missed assessments: indicators of poorer health prior to hospital admission (inability to walk 5 min (OR: 0.46; 0.23, 0.91), unemployment due to health (OR: 0.47; 0.23, 0.96), and alcohol abuse (OR: 0.53; 0.28, 0.97)) and having the preceding visit at the research clinic rather than at home/facility, or by phone/mail (OR: 0.54; 0.31, 0.96). Inversely, variables associated with higher odds of missed assessments at subsequent visits include: functional dependency prior to hospital admission (i.e. dependency with >?=?2 Instrumental Activities of Daily Living (IADLs) (OR: 1.96; 1.08, 3.52), and missing assessments at preceding visit (OR: 2.26; 1.35, 3.79). CONCLUSIONS:During the recovery process after hospital discharge, dependencies in physical functioning (e.g. ADLs, IADLs) prior to hospitalization and at hospital discharge were associated with higher odds of missed assessments. Conversely, other indicators of poorer health at baseline were associated with lower odds of missed assessments after the initial post-discharge visit. To reduce missing assessments, longitudinal clinical research studies may benefit from focusing additional resources on participants with dependencies in physical functioning prior to hospitalization and at hospital discharge.