Changes in peripheral inflammatory cytokines and clinical outcomes before and after deep brain stimulation in patients with Parkinson's disease with or without type 2 diabetes mellitus: an observational study.

BACKGROUND: Type 2 diabetes mellitus (T2DM) may influence clinical outcomes and inflammatory responses after deep brain stimulation (DBS) in patients with Parkinson's disease (PD). This study compared postoperative clinical and cytokine changes in patients with and without T2DM. METHODS: This observational study included 156 patients with PD undergoing first-time bilateral subthalamic nucleus DBS (78 with T2DM and 78 without T2DM). MDS-UPDRS III scores, levodopa equivalent daily dose (LEDD), Chinese Mini-Mental State Examination (CMMS) scores, BDI scores, and serum IL-1β, IL-10, and TNF-α levels were assessed before surgery and at 1 and 6 months after surgery. Exploratory analyses examined baseline HbA1c and individual cytokine trajectories. RESULTS: Before surgery, the T2DM group had a higher BMI and LEDD and lower CMMS scores, whereas no statistically significant between-group differences were observed in Med OFF MDS-UPDRS III scores or cytokine levels. Both groups showed postoperative reductions in MDS-UPDRS III and LEDD. At 6 months, no statistically detectable between-group difference in motor improvement rate was observed (P = 0.667). Between-group cytokine change estimates were small, but 95% confidence intervals crossed zero and did not establish equivalence. Exploratory analyses did not identify clear associations of baseline HbA1c or individual cytokine trajectories with 6-month motor outcome. CONCLUSIONS: In this selected cohort, T2DM was not associated with a statistically detectable reduction in short-term motor benefit after DBS. The observed cytokine changes were temporally associated with postoperative follow-up and should not be interpreted as evidence of a direct anti-inflammatory effect of DBS.