ABSTRACT
Health is complex and dynamic, influenced by both individual characteristics (genetics, biology, behavior) and an individual’s interaction with their social and physical environment over the course of a lifespan (Henly, Wyman, & Findorff, 2011). Understanding the factors (and timing of those factors) that influence health over time provides a basis for identifying individuals at risk for adverse trajectories or outcomes, and offers insight on the timing and effects of interventions to remediate compromised health. Equally important is the ability to identify and explain variation in health behaviors, health outcomes, and responses to interventions over time. Identification of population subgroups whose members’ health changes similarly over time provides the opportunity for tailoring interventions to specific individuals in those subgroups. In intervention research, assessment of health status over time permits characterization of response (quick or slow, temporary or durable, constant, or changing rate of change) and identification of responders and nonresponders (e.g., Muthén, Brown et al., 2002; Nies & Sun, 2008; Stein, Dickstein, Schuster, Litz, & Resick, 2012; Wills et al., 2012).
