Journal of Clinical Medicine Research, ISSN 1918-3003 print, 1918-3011 online, Open Access
Article copyright, the authors; Journal compilation copyright, J Clin Med Res and Elmer Press Inc
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Original Article

Volume 17, Number 2, February 2025, pages 76-88


Impact of Prior Metformin Use on Stroke Outcomes: A Systematic Review and Updated Meta-Analysis

Figures

Figure 1.
Figure 1. PRISMA flow diagram. PRISMA: Preferred Reporting Items for Systematic Reviews and Meta-Analyses.
Figure 2.
Figure 2. Forest plot of modified Rankin Scale (mRS 0 - 2) outcome. RR: risk ratio; CI: confidence interval; mRS: modified Rankin Scale.
Figure 3.
Figure 3. Forest plot of modified Rankin Scale (mRS 3 - 6) outcome. RR: risk ratio; CI: confidence interval; mRS: modified Rankin Scale.
Figure 4.
Figure 4. Forest plot of NIHSS at discharge outcome. SD: standard deviation; MD: mean difference; CI: confidence interval; NIHSS: National Institutes of Health Stroke Scale.
Figure 5.
Figure 5. Forest plot of NIHSS at admission outcome. SD: standard deviation; MD: mean difference; CI: confidence interval; NIHSS: National Institutes of Health Stroke Scale.
Figure 6.
Figure 6. Forest plot of mortality outcome. RR: risk ratio; CI: confidence interval.
Figure 7.
Figure 7. Forest plot of length of stay outcome. SD: standard deviation; MD: mean difference; CI: confidence interval.
Figure 8.
Figure 8. Leave-one-out meta-analysis for mRS 0 - 2. RR: risk ratio; CI: confidence interval; mRS: modified Rankin Scale.
Figure 9.
Figure 9. Leave-one-out meta-analysis for mRS 3 - 6. RR: risk ratio; CI: confidence interval; mRS: modified Rankin Scale.
Figure 10.
Figure 10. Leave-one-out of the meta-analysis for NIHSS at admission. MD: mean difference; CI: confidence interval; NIHSS: National Institutes of Health Stroke Scale.
Figure 11.
Figure 11. Leave-one-out of the meta-analysis for mortality. RR: risk ratio; CI: confidence interval.

Tables

Table 1. Summary Characteristics of the Included Studies
 
StudyStudy designCountryTotal participantsTime frameDuration of follow-upInclusion criteriaExclusion criteriaResults
MetforminNon-metformin
AIS: acute ischemic stroke; mRS: modified Rankin Scale; CT: computed tomography; MRI: magnetic resonance imaging; ICH: intracerebral hemorrhage; SAH: subarachnoid hemorrhage; ICD: International Classification of Diseases; IVT: intravenous thrombolysis; EVT: endovascular treatment; END: early neurological deterioration; END-prog: END as stroke progression; END-SHT: END as symptomatic hemorrhagic transformation; RT: reperfusion therapy; MT: mechanical thrombectomy; ASPECTS: Alberta Stroke Program Early CT Score; HbA1c: hemoglobin A1c; T2DM: type 2 diabetes mellitus; LAA: large-artery atherosclerosis; CES: cardioaortic embolic stroke; SVO: small-vessel occlusion; WHO: World Health Organization; NIHSS: National Institutes of Health Stroke Scale; N/A: not available.
Akhtar et al, 2022 [14]Prospective cohortQatar1,1321,0252013 - 2020N/AAll patients with acute stroke admitted to the Hamad General Hospital (HGH) and prospectively entered the Qatar Stroke databasePatients with stroke mimics, transient ischemic attacks, ICH, cerebral venous thrombosis, and new-onset diabetesPatients with diabetes on chronic pre-stroke treatment with metformin had improved recovery following the ischemic event.
Jian et al, 2023 [15]Retrospective cohortChina1241302017 - March 2021N/APatients: 1) were diagnosed with AIS by cranial CT or MRI; 2) the time from onset to admission was < 7 days; 3) were diagnosed with T2DM, including self-reported diabetes and newly diagnosed diabetes at admission.Patients with: 1) unclear hypoglycemic therapy before stroke onset or after admission; 2) a mRS > 1 before stroke onset; 3) an estimated glomerular filtration rate < 45 mL/min; 4) metformin withdrawal within 90 days; or 5) lost to follow-up.Patients with diabetes who were treated with metformin continuously before stroke onset and after admission had a better 90-day functional outcome.
Tu et al, 2022 [22]Prospective cohortChina3,5933,994August - September 201912 monthsAll patients with the first-ever stroke (ischemic stroke (ICD63), ICH (ICD61), and SAH (ICD60)) and T2DM were included. Patients were eligible for inclusion if admitted to the hospitals with a stroke defined according to the WHO criteria and with symptom onset within 14 days.Hospitals with a sample size of less than 50 and a follow-up rate of less than 80% will be excluded. Also, patients with 1) lack of informed consent; 2) lost to follow-up; and 3) lack of crucial clinical information (such as MT information (yes or no) and functional scores during follow-up) would be excluded.Metformin use in stroke patients with T2DM resulted in a less severe stroke and lower fatality and disability rates.
Kersten et al, 2022 [17]Retrospective cohortNetherlands5923452017 - June 2021N/AAll consecutive patients with AIS and known T2DM aged 18 years or older were included between 2017 and June 2021N/APre-stroke metformin use was associated with favorable outcomes in a large group of patients with T2DM after AIS.
Mima et al, 2016 [7]N/AJapan77163April 2010 - September 2014N/AOnly patients with brain infarction complicated by DM who were admitted to National Hospital Organization Kyushu Medical Center between April 2010 and September 2014 were included.Mild stroke severityMetformin use in stroke patients with T2DM resulted in a less severe stroke and lower fatality and disability rates.
Westphal et al, 2020 [19]Multicenter retrospective analysisSwitzerland757757N/AN/AData from patients diagnosed with type 2 diabetes before stroke or at the time of stroke based on admission HbA1c values ≥ 6.5% were included.Either diagnosed with type-1 diabetes or diabetes type was not specifiedStroke patients with diabetes on treatment with metformin receiving IVT had less severe strokes on admission and a better functional outcome at 3 months. This suggests that metformin has a protective effect, resulting in less severe strokes and beneficial thrombolysis outcomes.
Kim et al, 2024 [12]CohortKorea13794March 2015 - September 2023N/APatients with AIS with large artery occlusion of the anterior circulation who received EVT. Among these EVT-patients diagnosed as T2DM before stroke or who had an admission of HbA1c ≥ 6.5% at the time of stroke.Patients with a mRS score ≥ 2 before stroke, patients without initial brain CT or MRI scan within 24 h of stroke onset, patients with an ASPECTS > 6, and patients without a 3-month mRS scoreSubjects with prior metformin use, before EVT, the initial NIHSS and infarct volume were lower than those without prior metformin use. Prior metformin use could reduce the risk of END-prog and END-SHT after EVT and prior. Metformin use was associated with a 3-month mRS of 0 to 2 after EVT in patients with T2DM.
Akiyama et al, 2024 [13]Retrospective cohortJapan551052010 - 2021N/AOnly patients with ischemic stroke subtypes defined as LAA, CES, or SVO were consecutively selected, and T2DMPatients’ wide variety of etiologies of stroke, patients without antidiabetic agents before stroke, with only insulin, and with missing data on medication, and patients with a mRS score ≥ 3 before stroke onset were excluded.Metformin treatment before stroke was associated with lower stroke severity and favorable functional outcome.
Allahverdiyev et al, 2020 [20]CohortTurkey4228January 2017 - April 2019N/APatients with AIS and T2DMPatients had a hemorrhagic stroke, T1DM, severe renal failure and severe deterioration in daily life activities before stroke (mRS score ≥ 3)There was not any significant difference between the groups of severity and prognosis of AIS.
Abbasi et al, 2018 [21]RCTIranN/AN/AN/A3 monthsIschemic stroke patients and focal neurological symptomsPatients with ICH, SAH, subdural hematoma (SDH), hypoglycemia, contraindications for metformin use, venous sinus thrombosis, and drug side effects and diabetic patients.There was a significant difference in metformin taking in the reduction of NIHSS score in non-diabetic stroke patients. There was a significant association between metformin taking and a decrease in NIHSS scores in patients with cortical ischemic stroke.
Curro et al, 2022 [18]Retrospective cohortN/AOverall = 170February 2014 - December 2019N/APatients underwent IVT within 4.5 h after ischemic stroke onset. Patients underwent MT within a time frame from symptom onset to treatment ≤ 6 h for anterior circulation and ≤ 24 h for posterior circulation.Patients with large territorial infarction are defined as ASPECTS < 5, hospital arrival beyond the time window, and elevated bleeding risk for IVT.A lower mRs was associated with lower glycemia and admission NIHSS (aNIHSS) in all RT and MT; lower aNIHSS and younger age in IVT.

 

Table 2. Baseline Characteristics of the Included Population
 
CountryAuthor, yearStudy designGroupNumber of participantsBasic patient characteristicsRisk factorsOn admission parameters
Age (years), mean (SD)Sex (males), nBMI, mean (SD)HbA1c %, mean (SD)DBP, mean (SD)SBP, mean (SD)Hypercholesterolemia, nHypertension, nAtrial fibrillation, nCurrent smoking, nStroke-to-needle-time (min), mean (SD)CHD, nGlucose (mg/dL), mean (SD)Creatinine (mmol/L), mean (SD)Platelets, mean (SD)INR, mean (SD)History of previous stroke, n
BMI: body mass index; SD: standard deviation; CHD: coronary heart disease; INR: international normalized ratio; DBP: diastolic blood pressure; SBP: systolic blood pressure; MET: metformin; HbA1c: hemoglobin A1c.
QatarAkhtar et al, 2022 [14]Prospective cohortMet +1,13254.4 (13.2)910-7.5 (2.5)--6238484835059.9 (35.4)131-95.8 (64.4)--134
Met -1,02554.6 (13.1)842-7.6 (4.3)--5377664227659.8 (39.8)112-97.0 (66.6)--137
ChinaJian et al, 2023 [15]Retrospective cohortMet +12463.16 (12.33)87-8.1 (2)85.88 (13.93)152.39 (23.26)1199736-19224.6 (40.5)57.43 (16.45)206.35 (70.06)0.93 (0.08)39
Met -13065 (13.49)78-8.5 (2.2)82.8 (12.9)148.5 (22.4)18951240-29234.52 (74.16)59.73 (19.34)199.67 (74.22)0.93 (0.07)39
ChinaTu et al, 2022 [22]Prospective cohortMet +3,59364.67 (11.12)2,015----8672,789167--------
Met -3,99465.67 (12.61)2,336----9673,158254--------
NetherlandsKersten et al, 2022 [17]Retrospective cohortMet +59275 (10)33228 (4.46)---16467-182--174.6 (48.2)---Excluded from the study
Met -34576 (11)16728 (4.47)---10841-87--166.86 (63)---Excluded from the study
JapanMima et al, 2016 [7]Met +7767.7 (10.3)5625.7 (5.5)7.5 (1.2)83 (17)154 (25)5264-20-9175 (71)----
Met -16373.2 (9.2)11923.6 (3.2)7.3 (1.3)85 (17)160 (27)93133-45-21179 (70)----
SwitzerlandWestphal et al, 2020 [19]Multicenter retrospective analysisMet +75771.4 (9.5)47884.1 (16.8)-83.2 (16.2)159.6 (24.8)481673176135161.4 (96.8)183169.2 (63)87.0 (47.7)232.5 (71.3)1.0 (0.2)145
Met -75771.8 (10.9)458---158.8 (25.9)450656187139158.4 (120.2)182169.2 (70.2)92.0 (51.7)238.3 (79.8)1.0 (0.1)271
KoreaKim et al, 2024 [12]CohortMet +13771.2 (11.5)76-7.5 (1.4)-151.7 (26.5)32947318123 (48.9)-180.8 (70.1)97.26 (53.05)-1.06 (0.29)34
Met -9472.5 (13.1)49-7.2 (1.6)-151.9 (28.3)26685013121 (56.3)-175.6 (86.7)106.1 (106.1)-1.03 (0.18)32
JapanAkiyama et al, 2024 [13]Retrospective cohortMet +5573.3 (11.4)4422.9 (2.7)7.37 (0.99)84.7 (17.5)161.7 (31.2)3544-33-8175.3 (73)75.16 (17.68)--15
Met -10573.3 (8.3)7823 (3.4)7 (0.98)84.7 (16.5)160 (26.3)7089-59-20158.3 (57.1)85.77 (43.33)--28
TurkeyAllahverdiyev et al, 2020 [20]CohortMet +4270.02 (10.92)18-8.11 (1.78)80.71 (14.69)145.33 (27.86)1034410-17144.94 (60.74)---7
Met -2868.43 (11.09)16-8.84 (3.16)81.32 (17.83)155.8 (33.24)826213-11159.23 (87.31)---4
IranAbbasi et al, 2018 [21]RCTMet +Overall 10068.9 (10.6)Overall 50---------------
Met -67 (11.63)---------------
ItalyCurro et al, 2022 [18]Retrospective cohortMet +Overall 17076.72 (8.72)84--81.88 (15.52)154.81 (25.53)56140-26251.88 (107.26)47185.33 (69.52)96.38 (49.52)237.73 (91.96)-31
Met -