Coffee Consumption, Serum Copeptin, and Selected Echocardiographic Parameters in Patients with ADPKD: A Cross-Sectional Study

Background/Objectives: Coffee consumption has been suggested to influence arginine vasopressin-related pathways and cardiovascular function. However, its relationships with serum copeptin and cardiac parameters in patients with autosomal dominant polycystic kidney disease (ADPKD) remain unclear. This study aimed to investigate the association between habitual coffee consumption and serum copeptin concentrations and selected echocardiographic parameters in patients with ADPKD. Methods: In this cross-sectional study, 73 patients with ADPKD were classified as coffee consumers (n = 35) or non-consumers (n = 38). Serum copeptin measurements were available for 62 patients. Coffee consumption was assessed using a standardized questionnaire and expressed as grams of dry coffee per month. Multivariable models were used to assess associations with log-transformed copeptin, mitral annular e′ velocity, and E/e′ ratio. Results: Serum copeptin levels were lower among coffee consumers than non-consumers (median, 263.51 vs. 332.77 ng/L; p = 0.013). After adjustment, coffee consumption was associated with lower log-transformed copeptin levels (B = −0.263; p = 0.047), although this association was not statistically significant when using heteroskedasticity-consistent (HC3) robust standard errors (p = 0.074). Coffee consumers had higher mitral annular e′ velocity (8.61 vs. 5.86 cm/s; p < 0.001), which remained significant after adjustment (B = 2.531; p < 0.001), and a lower E/e′ ratio (B = −4.548; p = 0.007). Conclusions: In this ADPKD cohort, coffee consumption was associated with lower serum copeptin levels, higher mitral annular e′ velocity, and lower E/e′ ratio. These findings raise the hypothesis that habitual coffee consumption may be associated with vasopressin–copeptin system activity and diastolic myocardial relaxation in patients with ADPKD. However, the copeptin association was not robust to HC3 analysis, and the echocardiographic findings should be considered exploratory.