Do insomnia and physical activity mediate the relationship between diabetes and depression in people with type 2 diabetes?

Purpose: To examine how self-reported depressive symptoms are affected by type 2 diabetes, and how this relationship may be mediated by insomnia and physical activity. Methods: We used cross-sectional data from the Health In Central Denmark (HICD) cohort including persons with and without type 2 diabetes aged 18 to 75 years. Register-identified diabetes status was used as the exposure and The World Health Organization Five Well-Being Index (WHO-5) was used as the outcome measure for risk of depression. Insomnia severity index level and physical activity level were used as potential mediators. We performed logistic regression analyses and cross-sectional mediation analyses. Results: In total, 45,988 participants were included. Of these, 19,907 had type 2 diabetes of which 1,396 were at risk of depression. Adjusted odds ratio (OR) for risk of depression in people with type 2 diabetes was 1.55 (95% confidence interval (CI): 1.19, 1.59). The strongest risk factor for depression was insomnia at an adjusted OR of 7.43 (CI: 6.63, 8.32). The relationship between diabetes and risk of depression may be mediated by both insomnia and physical activity, the proportion mediated being 42.1% for insomnia and 20.5% for physical activity, in our analyses. Conclusion: Living with type 2 diabetes was associated with higher odds of depression, and insomnia and physical activity may mediate this relationship. Insomnia and physical activity may be important factors for healthcare professionals to consider in their treatment of people with type 2 diabetes.