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Table 1 Study characteristics of 16 prospective observational studies included in the meta-analysis

From: Association between thyroid dysfunction and type 2 diabetes: a meta-analysis of prospective observational studies

Author, publication year

Cohort, country

Design, follow-up years

Population, cases/total no. of subjects

Age (years), female (%), and ethnicity

BMI (kg/m2), thyroid medicine users (%)

Outcomes

Covariates adjusted in models

M Thvilum, 2013 [32]

Official Danish health registers study, Denmark

Prospective cohort study, mean: 6 years

Danish national patient registry population, 1020/14,480

Mean: 58, 84% of women, NR

NR, no

T2DM

Age and sex.

N Gronich, 2015 [2]

NR, Israel

Prospective cohort study, 5–7 years

Statin non-users 3666/20,334

40–80, 62.11% of women, NR

Obesity (43.63%), mixed

DM

Age, sex, race, obesity, smoking, glucose, LDL, HDL, TG, history of hypertension, and drug use.

N Gronich, 2015 [2]

NR, Israel

Prospective cohort study, 5–7 years

Statin users, 4410/39,263

40–80, 62.24% of women, NR

Obesity (44.3%), mixed

DM

Age, sex, race, obesity, smoking, glucose, LDL, HDL, TG, history of hypertension, and drug use.

J-E Jun, 2016 [33]

NR, Korea

Prospective cohort study, 7 years

Population-based, 229/6235

≥ 18, 41.96% of women, NR

Mean (SD): 23.7 (2.56), no

T2DM

Age, sex, BMI, HbA1c, HDL, TG, LDL, smoking, lipid drug use, hypertension, BMI change.

L Mehran, 2016 [34]

Tehran Thyroid Study, Iran

Prospective cohort study, median: 9.73 years

Population-based, NR/2316

≥ 20, NR, NR

Mean (SD): 25.3 (4.3), no

High-fasting blood glucose

Age, sex, smoking, BMI, and HOMA-IR.

L Chaker, 2016 [35]

The Rotterdam Study, Netherlands

Prospective cohort study, mean: 7.9 years

Healthy population-based, 757/8107

Mean: 64.6, 58% of women, NR

Mean (SD):  26.5 (4.05), mixed

DM

Sex, age, smoking, cohort, FSG levels, insulin, SBP, DBP, antihypertensive drugs, HDL cholesterol, and BMI.

C-H Chang, 2017 [27]

NR, China

Prospective cohort study, median: 2.6 years

Population-based, 1551/68,846

Mean: 41.2, 52.5% of women, NR

Obesity (3.2%), no

Dysglycemia, prediabetes, and T2DM

Sex, age, education level, smoking, drinking, and obesity.

N M.Y. Journy, 2017 [36]

U.S. radiologic technologist cohort, USA

Prospective cohort study, median: 28 years

Women, 163/75,076

20-89, 100% of women, multiple

NR, mixed

T2DM deaths

Baseline year, age, race, BMI, family history of breast cancer, lifestyle, reproductive factors.

T. Ittermann, 2017a [37]

Study of Health in Pomerania, Germany

Prospective cohort study, median: 5 years

Population-based, 116/2689

20–79, 51.2% of women, NR

Mean (SD): 27.2 (4.7), mixed

T2DM

Age and sex.

T. Ittermann, 2017a [37]

INTER99, Denmark

Secondary analysis of RCT, 5 years

Population-based, 142/3815

30–60, 49.9% of women, NR

Mean (SD): 26.3 (4.6), NR

T2DM

Age and sex.

T. I. de Vries, 2018 [38]

SMART study, Netherlands

Prospective cohort study, 2.9–8.3 years

With high cardiovascular risk, 289/5542

Mean: 56, 35.24% of women, NR

Mean (SD): 26.72 (4), no

T2DM

Age, sex, current smoking, total and HDL cholesterol, and triglycerides

R-H Chen, 2019 [39]

NR, China

Prospective cohort study, 10 years

Population-based, 5485/91,120

≥ 18, 77.4% of women, NR

Obesity (0.7%), NR

T2DM

Age, sex, and comorbidities.

H-S Chen, 2007 [40]

NR, China

Prospective cohort study, 3–4.3 years

T2DM patients, CVD: 61, CVD deaths: 12, deaths: 31/556

≥ 30, 35.07% of women, NR

Mean (SD): 26.11 (9.8), mixed

CVD events, CVD deaths, and all-cause deaths

Age, sex, HbA1c, TC, HDL, BP, BMI, smoking, medication, urinary albumin, creatinine

C Drechsler, 2014 [41]

NR, China

Prospective cohort study, 4 years

Diabetic hemodialysis patients, sudden death: 120 MI: 156, stroke: 70, CV events: 345, deaths: 441/ 934

18-80, 46.26% of women, NR

Mean (SD): 27.6 (4.98), NR

Sudden death, MI, stroke, combined CV events, all-cause death

Age, sex, atorvastatin, SBP, BMI, left ventricular hypertrophy, albumin, creatinine, N-terminal pro2B-type natriuretic peptide, ultrafiltration volume.

J Geng, 2014 [42]

NR, China

Prospective cohort study, 2–3 years

T2DM patients, CHD: 32, new AF: 14, deaths: 10/694

Mean: 56.1, 32.75% of women, NR

Mean (SD): 25.13 (3.63), NR

CHD events, new-AF, and all-cause deaths

Age, sex, hypertension, total cholesterol, LDL-cholesterol, smoking, SBP, DBP, and BMI.

T I. de Vries, 2019 [26]

SMART study, Netherlands

Prospective cohort study, 3.3–9.6 years

T2DM patients, CVD: 191, deaths: 204/1265

Mean 61, 26.64% of women, NR

Mean (SD): 29.22 (5), NR

CVD, all-cause deaths

Age, sex, smoking, history of vascular disease, eGFR, SBP, TC, and HDL-C.

  1. Abbreviations: NR not reported, BMI body mass index, DM diabetes mellitus, T2DM type 2 diabetes mellitus, LDL low-density lipoprotein, HDL high-density lipoprotein, TG triacylglycerol, TC cholesterol, AF atrial fibrillation, BP blood pressure, SBP systolic blood pressure, DBP diastolic blood pressure, CVD cardiovascular disease, MI myocardial infarction, CHD coronary heart disease, FSG fasting serum glucose, eGFR estimated glomerular filtration rate
  2. aThese two studies were extracted from one article