Sociodemographic, Clinical, and Psychosocial Predictors of Short- and Long-term Study Retention in the Diabetes Prevention Program (DPP) Outcomes Study (DPPOS)

Abstract

Objective: Success of longitudinal studies depends on retention of participants. We examined characteristics as predictors of retention among participants with prediabetes and type 2 diabetes (T2D) in the Diabetes Prevention Program (DPP) and the follow-up DPP Outcomes Study.

Research design and methods: A total of 3,234 adults at high risk of T2D joined the DPP (1996-1999, mean age 51 ± 10 years). They were randomized to lifestyle, metformin, or placebo intervention, and then followed through 2020. Logistic regression models estimated the association between baseline sociodemographic, clinical and psychosocial characteristics (life events, family functioning, social support), and short-term retention (∼3 years). Cox proportional hazards models, censoring at death, estimated the association between baseline and time-varying characteristics and time to dropout over the entire 20 years of follow-up.

Results: Among surviving participants (n = 3,218), 93% were retained after 3 years, and 75% of those surviving remained engaged over 20 years. Younger age was associated with dropout during DPP and over 20 years of follow-up. Female sex, non-White race and ethnicity, employment, and lack of baseline depressive symptoms were associated with better long-term retention. Over time, better health state (SF-36) (hazard ratio [HR]: 0.89 per 0.1 point; 95% CI: 0.83-0.95) was associated with retention. Greater BMI (HR: 1.06 per 5 kg/m2; 95% CI: 1.00-1.12), more recent life events (HR: 1.08; 95% CI: 1.02-1.14), and depressive symptoms (HR: 1.11 per 5 points; 95% CI: 1.05-1.18) were associated with reduced retention. Among adults 45-59 years of age at baseline, development of T2D was associated with better retention (HR: 0.75; 95% CI: 0.58-0.97).

Conclusions: Twenty-year retention of a racially and geographically diverse cohort with prediabetes is possible. Retention was associated with age, psychosocial factors, T2D development, and BMI.

Graphical abstract

Figure 1

Probability of loss to follow-up by age-group over 20 years.

Figure 2

Association of time-varying characteristics for long-term dropout (time to last visit over 20 years), among cohort surviving at end of DPP, n = 3,218. Shown are Cox proportional HR and 95% CI. Outcome is time to last visit attended (i.e., dropout). Censoring at death date if participant attended a visit within previous 1 year of date of death. Administrative censoring of all remaining participants at 20 years since randomization. HR >1 signifies greater likelihood of dropout, that is, association with worse retention. Conversely, HR <1, signifies lower likelihood of dropout, that is, association with better retention. A: Each time-varying characteristic modeled separately, adjusted for select baseline characteristics treatment group, age (per 10 years), sex, race and ethnicity, education, income group, marital history, household size, and employment. *Entered into model simultaneously to adjust for one another. B: A significant interaction was observed between time-varying diabetes status and age (P = 0.03); however, the interaction with time-varying BMI did not reach statistical significance (P = 0.11). Diabetes status and BMI were modeled simultaneously to adjust for one another. Model also adjusted for sex, race and ethnicity, education, income group, marital history, household size, and employment.