Abstract

Background: Patients with coronary heart disease (CHD) complicated by diabetes mellitus (DM) remain at substantial residual cardiovascular risk despite contemporary guideline-directed medical therapy. However, the long-term trajectory of this excess risk and its temporal pattern have not been fully clarified. Methods: This is a retrospective cohort study based on a large-scale public database and real-world clinical data. The primary cohort was derived from the UK Biobank (UKB), including 7491 CHD patients and 2322 CHD with DM patients; the validation cohort included 362 CHD patients from Tongji Hospital. Both cohorts were followed for up to 10 years, with major adverse cardiovascular events (MACE) as the primary endpoint. Propensity score matching (PSM) was employed to balance baseline confounders. Kaplan–Meier analysis combined with piecewise log-rank tests were used to assess cumulative risk differences at various follow-up time points. Multivariable Cox proportional hazards models were constructed to evaluate the independent impact of diabetes. Results: In the UKB cohort, CHD with DM patients exhibited significantly higher risks of MACE and cardiovascular death before matching. After 1:1 PSM, no significant difference in MACE risk was observed during the early follow-up period (1 year, p > 0.05). However, survival curves showed progressive divergence over time, with the risk difference reaching statistical significance at 10 years (p = 0.0004), demonstrating a pronounced time-cumulative effect. The Tongji validation cohort similarly confirmed that event-free survival was significantly lower in the CHD with DM group (p = 0.0028). Independent risk factor analysis using multivariable Cox regression showed that after adjusting for age, sex, smoking, and lipid parameters, diabetes remained an independent risk factor for long-term MACE (UKB cohort HR > 1; Tongji cohort HR = 1.86, 95% CI: 1.20–2.86, p = 0.005). Conclusions: Diabetes significantly increases the long-term residual cardiovascular risk in CHD patients. This excess risk is characterized by a clear time-cumulative effect: under modern guideline-directed medical therapy, early risk may be effectively buffered, but long-term adverse events remain markedly elevated. More proactive and intensified long-term intervention strategies are urgently needed for CHD patients with comorbid diabetes.

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