Table 1 Characteristics of included studies in the meta-analysis
Studies | Country | Study design | Sample size/Cases | Gender, age range | Exposure assessment | Outcome | comparison | HR or OR (95% CI) | Adjustment for covariate | Follow up (years) | NOS scores |
|---|---|---|---|---|---|---|---|---|---|---|---|
Faglia,E.2002 | Italy | Cohort | 735/42 | M,F 40–65 years | - | Cardiac events | C-peptide (nmol/l) | HR= 0.99 (0.96– 1.04) | - | 5 years | 8/9 |
Pikkemaat,M.2019 | Sweden | Cohort | 398/40 | M,F 52.4 ± 8.7 years | Laboratory analyses | Ischemic stroke events | C-peptide (Per 1 nmol/ l) | HR= 1.22 (0.62– 2.39) | Age, sex, smoking, systolic blood pressure, HbA1c, antihypertensive treatment, BMI, CRP, eGFR, cholesterol, and previous myocardial infarction or ischemic stroke | 17 years | 8/9 |
Pikkemaat,M.2019 | Sweden | Cohort | 398/51 | M,F 52.4 ± 8.7 years | Laboratory analyses | Myocardial infarction events | C-peptide (Per 1 nmol/ l) | HR= 1.47 (0.84– 2.58) | Age, sex, smoking, systolic blood pressure, HbA1c, antihypertensive treatment, BMI, CRP, eGFR, cholesterol, and previous myocardial infarction or ischemic stroke | 17 years | 8/9 |
Schrauben,S.2019 | U.S | Cohort | 1883/220 | M, F 56.5 ± 11.9 years | NA | Atherosclerotic CVD events | C-peptide Per 1 SD | HR = 1.02 (0.84–1.24) | Age, sex, race, ethnicity, level of education, clinical center, BMI, waist circumference, smoking status, systolic BP, ACEi/ARB use, HDL, LDL, triglycerides, high sensitivity CRP, fat-free mass, eGFR, hemoglobin, physical activity, use of statins, use of other lipid-lowering medications, history of CVD, 24-h urine protein, FGF-23, uric acid, serum albumin | 7.7years | 9/9 |
Bo, S.2012 | Italy | Cohort | 2113/278 | M, F 66.9 ± 10.2 years | Enzyme immunoassay | CVD events | C-peptide (T3 vs. T1) | HR = 0.93 (0.68–1.27) | Age, sex, BMI, smoking, time since diagnosis, insulin treatment, values of HbA1c, systolic blood pressure, HDL-cholesterol and triglycerides, presence of retinopathy, nephropathy, neuropathy and cardiovascular diseases | 14years | 9/9 |
Panero,F.2009 | Italy | Cohort | 471/NA | M, F 38.6 ± 9.4 years | NA | Macro vascular complications events | C-peptide (nmol/l) | HR = 0.77 (0.38–1.58) | Age, sex, diabetes duration, individual cumulative A1C average during the study period, hypertension, and cardiovascular diseases | 10years | 8/9 |
Panero,F.2009 | Italy | Cohort | 471/242 | M, F 38.6 ± 9.4 years | NA | Micro vascular complications events | C-peptide (nmol/l) | HR = 0.59 (0.37–0.94) | Age, sex, diabetes duration, individual cumulative A1C average during the study period, hypertension, and cardiovascular diseases | 10years | 8/9 |
Koska,J.2021 | U.S | Cohort | 1693/479 | M-F, 60 ± 9 years | Radioimmunoassay | CVD events | C-peptide (nmol/l) | HR = 1.27 (1.00–1.63) | Glucose lowering group, clinical and demographic risk factors, baseline insulin and sulphonylureas, severe hypoglycaemia. | 5.3years | 9/9 |
Dong, M.2013 | China | Case–control | Control = 60 Case = 30 | F 69.4 years | Chemoluminescence method | Acute myocardial infarction events | C-peptide (ng/ml) | OR = 1.45 (0.55–3.82) | Oestrone, oestradiol, testosterone, WHR, BMI, hypertension, diabetes and SHBG | - | 8/9 |
Winocour,P.1992 | UK | Cross-sectional | 90/23 | M, F 17–70 years | Radioimmunoassay | CHD events | C-peptide (nmol/l) | OR = 1.98 (0.13–29.3) | NA | - | 5/7 |
Chen,Z.2021 | U.S | Cross-sectional | 3752/1832 | M-F, 60.2 ± 13.1 years | Radioimmunoassay | SC-MI events | C-peptide (Q4 vs. Q1) | OR = 1.48 (1.18–1.87) | Age, gender, race, smoking, drinking, physical activity, BMI, TC, triglycerides, CRP, creatinine, glucose, glycated hemoglobin, and insulin | - | 7/7 |
Li,W.2014 | U.S | Cross-sectional | 7030/143 | M-F, 12–85 years | Radioimmunoassay | Stroke events | C-peptide (nmol/L) | OR = 3.71 (1.78–7.75) | Age, sex, ethnicity, height, weight, education level, physical activity, smoking status, alcohol use, HDL, LDL, triglycerides. | - | 7/7 |
Wang,Y.2019 | China | Cross-sectional | 3143/ 936 | M, F > 18 years | Immunoassay | CVD events | C-peptide (Q4 vs. Q1) | OR = 1.27 (1.13–1.42) | Age, gender, diabetes duration, current smoking, HbA1c, dyslipidemia, BMI, hypertension, use of insulin, statins, insulin-secreting agents. | - | 7/7 |
Pontiroli,A.1997 | Italy | Cross-sectional | 93/54 | M-F, 59–77 years | Radioimmunoassay | CHD events | C-peptide per 1 unit | OR = 1.47 (1.15–1.86) | - | - | 5/7 |
Chung,J.2019 | Korea | Cross-sectional | 939/191 | M-F, 62.6 years | Radioimmunoassay | CAN events | C-peptide (nmol/l) | OR = 0.67(0.52–0.87) | Age, gender, BMI, hypertension, hyperlipidemia, hemoglobin A1C, diabetes duration, CRP, anti-diabetic therapy UACR and eGFR. | - | 7/7 |
Wang,L.2015 | China | Cross-sectional | 501/291 | M-F 67.0 ± 8.0 years | Chemiluminesence immunoassay | CAD events | C-peptide (ng/mL) | OR = 1.51 (1.13–2.01) | Age, gender, BMI, duration of T2DM, history of insulin secretagogues treatment, insulin treatment and other anti-diabetic medications, fasting glucose, fasting plasma insulin, hypoglycaemic episodes, smoking and drinking statuses, UA, eGFR, hypertension and dyslipidemia UA, uric acid; eGFR, estimated glomerular filtration rate | - | 6/7 |