Risk of hyperlactatemia in patients with obstructive sleep apnea receiving metformin: a cross-sectional study

Type 2 diabetes is a common comorbidity in individuals with obstructive sleep apnea (OSA). Metformin, one of the most commonly applied therapy options for type 2 diabetes, is known to increase lactate production. Given that OSA may put patients at risk of hyperlactatemia, it is important to examine lactate levels in patients receiving metformin. This study aimed to identify factors affecting lactate concentrations and the consequent risk of hyperlactatemia in this population. A total of 505 patients were included in the study. All underwent a detailed and systematic clinical evaluation and attended diagnostic nocturnal polysomnography. Serum lactate levels were measured at a single time point. Median lactate concentration across the cohort was 1.0 mmol/L and did not differ by OSA severity (p = 0.82). 18.8% of patients used metformin and exhibited higher lactate concentrations compared to those not receiving the medication (p < 0.001). Elevated lactate levels (> 0.8 mmol/L) were detected in 64.8% of patients. Patients with increased lactate levels were more often active smokers. Multivariable analysis revealed that hyperlactatemia was associated with metformin use (p < 0.001) and active smoking (p = 0.014). Our findings indicate that metformin use in patients with OSA and type 2 diabetes appears to be safe for lactate metabolism, regardless of OSA severity. However, the risk of hyperlactatemia increases in actively smoking patients treated with metformin, which calls for targeted interventions to encourage smoking cessation in this population.