The length of hospital stay in COVID-19 patients using pre-hospital metformin at a Saudi tertiary hospital: a retrospective cohort study

BACKGROUND: Type 2 diabetes mellitus (T2DM) is prevalent in Saudi Arabia and is associated with severe outcomes from Coronavirus Disease 2019 (COVID-19). Metformin, the most prescribed medication for T2DM, has shown potential antiviral and anti-inflammatory properties that may be relevant in patients with COVID-19. This study evaluated the association of pre-hospital metformin use with length of hospital stay and secondary outcomes among patients with COVID-19 and T2DM. METHODS: This retrospective cohort study was conducted at King Abdulaziz Medical City in Jeddah from 2020 to 2023 and included hospitalized adult patients with confirmed COVID-19 and pre-existing T2DM. Pre-hospital metformin use was defined as documented within 90 days before hospital admission. Clinical characteristics, treatments, and hospital outcomes were analyzed using electronic health record data. RESULTS: Metformin use was associated with a significantly shorter hospital stay, with a median time to discharge of five days (95% CI: 4-6) compared with 14 days (95% CI: 7-44) in the non-metformin group. Metformin use was associated with a higher hazard of discharge than nonuse (HR = 1.85, 95% CI: 1.14-3.0; p = 0.012). No statistically significant differences were observed between the two groups for secondary outcomes, including mechanical ventilation, intensive care unit admission, and respiratory complications, defined as acute respiratory distress syndrome and severe respiratory failure. CONCLUSION: Among hospitalized patients with type 2 diabetes and COVID-19, metformin use was associated with shorter hospital stays and a higher discharge rate. However, given the retrospective, single-center design, potential survivor bias, and residual confounding, these findings should be interpreted cautiously. Prospective multicenter studies using competing-risk approaches and incorporating mortality outcomes are recommended.