Social Integration, Social Support and Incident Type 2 Diabetes: Results from the Prospective Heinz Nixdorf Recall Cohort Study

Background and Objectives: Aspects of social relationships, like isolation and low social support, have been linked to type 2 diabetes onset, though evidence is inconsistent. We investigated whether social relationships mediate the association between socioeconomic status (SES) and diabetes or interact with SES in relation to diabetes. Materials and Methods: The study included 3642 participants (mean age 58.9 ± 7.6 years, 47.9% male) from the Heinz Nixdorf Recall Study, a population-based cohort in Germany. Baseline examinations took place in 2000–2003 with two 5-year follow-ups. Adjusted relative risks (RRs) were estimated for social relationships (isolation, partnership, instrumental, financial, emotional support) and incident diabetes using Poisson regression with robust variance. We performed causal mediation analyses and estimated relative excess risks due to interaction (RERI). Results: Associations between measures of social integration and diabetes incidence were weak (e.g., RR = 1.09 (95% CI: 0.86, 1.39) for lack of partnership). Limited financial support was associated with higher diabetes risk (RR = 1.33 (1.09, 1.62)), whereas instrumental or emotional support was not. Some evidence of mediation was found for limited financial support (14% (95% CI: −7%, 35%) for the income–diabetes association). There was hardly any excess risk of diabetes in persons with poor education, and poor income, respectively, and low social support (RERI = −0.33 to 0.27). Conclusions: In this prospective study, limited financial support emerged as a social risk factor for type 2 diabetes and explained a small proportion of socioeconomic inequalities in diabetes incidence. Other dimensions of social relationships showed little evidence of independent, mediating, or interaction effects. The findings regarding financial support require confirmation in further studies.