Patterns of Cohort Participation Among People with Systemic Sclerosis in an Open Cohort: a Scleroderma Patient-centered Intervention Network Cohort Study.

Participants who continue across the full duration of longitudinal studies often differ from those lost to attrition, defined as discontinuing participation for any reason, and some participants may sporadically miss assessments. Complex participation patterns, such as in multicenter chronic disease cohorts, have not been studied. We aimed to implement an approach to identify participation subgroups and factors associated with theses. We applied our approach in the SPIN Cohort, a multicenter, longitudinal systemic sclerosis (SSc) cohort, because it is an example of an open-ended cohort with no planned end date and complex participation patterns. We used group-based trajectory modeling to identify participation subgroups and multinomial logistic regression to identify predictors of subgroup membership. Data were obtained for 2883 participants from 54 sites in 7 countries. We identified 5 participation subgroups: Ongoing Participation (29%), Immediate Attrition (29%), Mid-Term Attrition (19%), Long-Term Attrition (12%), and Ongoing Sporadic (11%) participation. Older age and sites outside the United States were associated with lower odds of belonging to all subgroups other than Ongoing Participation. Compared to Ongoing Participation, several sociodemographic variables were associated with higher odds of being in the Immediate Attrition group. Our method can be applied to other cohorts with complex participation patterns.