Nurturing Longitudinal Samples 2.0.

Background: While longitudinal designs can provide significant advantages compared to single measurement/cross sectional designs, they require careful attention to study infrastructure and the risk of attrition among the sample over multiple time points.
Objective: The strategies used to design and manage an appropriate infrastructure for a longitudinal study and approaches to retain samples are explored using examples from 2 studies, a 25-year study of persons living with multiple sclerosis and a 10-year longitudinal follow-up of breast cancer survivors.
Results: Key strategies (developing appropriate infrastructure, minimizing costs to participants, and maximizing rewards of study participation) have helped address the serious threat of attrition in these longitudinal samples.
Conclusion: Implementation of these strategies can help mitigate some of the disadvantages and leverage the strengths of longitudinal research to produce reliable, insightful, and impactful outcomes.
Competing Interests: Declaration of Conflicting InterestsThe author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.