Negative Impact of Diabetic Polyneuropathy on Muscle Weakness in the Lower Extremities of Older Patients Undergoing Coronary Artery Bypass Graft Surgery: A Retrospective Cohort Study

Background: Cardiovascular surgery causes muscle weakness associated with increased inflammatory cytokines. Diabetes mellitus (DM), through insulin resistance and diabetic polyneuropathy (DPN), promotes postoperative muscle weakness and is linked to elevated inflammatory cytokines. Identifying the effect of DM, particularly DPN, on postoperative muscle weakness could help target interventions to reduce physical disability. Purpose: This study aimed to identify whether DPN predicts postoperative muscle weakness in older adults undergoing coronary artery bypass grafting. Methods: Patients aged ≥65 years who underwent elective coronary artery bypass grafting were divided into 3 groups: those without DM (non-DM; n = 68), those with DM but without DPN (without-DPN; n = 28), and those with DPN (with-DPN; n = 24). Grip strength (GS) and isometric knee extensor strength (IKES) were measured pre- and postoperatively, and percent changes were calculated from baseline to discharge. The percent change in GS and IKES was compared among the 3 groups. In addition, a 2-way repeated-measures analysis of variance was conducted to compare muscle strength changes among groups, adjusting for potential confounders. Results: The percent change in IKES was significantly greater in the DPN group, with values of −3.2% in the non-DM group, −6.3% in the without-DPN group, and −14.3% in the DPN group ( P = .018). No significant differences were observed in GS changes among the groups. A 2-way repeated-measures analysis of variance revealed a significant group effect for GS ( P = .018, partial η 2 = 0.069) but no time effect or interaction. A significant time × group interaction was found for IKES ( P = .036, partial η 2 = 0.057), indicating differing strength change patterns between groups. Discussion: Patients with DPN had greater lower-extremity muscle weakness after surgery than those without DM and those with DM without DPN. These findings highlight the critical need for preventive strategies to mitigate physical disability in patients with DPN. Conclusions: Older adults with DPN may have an increased risk of developing postoperative muscle weakness in the lower extremities.