Table 1 Characteristics of the individual studies included in this systematic review and meta-analysis
First author year of publication | Location | Age years | Male (%) | Sample Size | Study design | Exposure definition | Original SUA value (umol/L), OR for HU or RR for gout (95%CI) | Type of tea | Adjustments | Outcome |
|---|---|---|---|---|---|---|---|---|---|---|
David Curb 1986 [48] | USA | 54.1 | 100 | 5858 | Cohort | 0 cups/day 1–2 cups/day 3–4 cups/day  > 5 cups/day | Not mentioned | Not mentioned | NA | SUA |
Tang 1998 [44] | China | 58.3 | 75 | 416 | Cross-Sectional | 0 gram/day ≤5 grams/day >5 grams/day | 325.4 (312.1–338.7) 339.4 (326.1–352.7) 354.2 (339.1–369.3) | Not mentioned | NA | SUA |
Kiyohara 1999 [32] | Japan | 52.0 | 100 | 2240 | Cross-Sectional | <1 cups/day 1–2 cups/day 3–4 cups/day >5 cups/day | 335.7 (327.4–344.6) 344.6 (336.9–353.0) 341.1 (333.9–348.8) 339.9 (332.1–347.6) | Green tea | Hospital, age, serum total cholesterol, serum HDL-cholesterol, serum creatinine, systolic blood pressure, BMI, rank, beer, alcohol, smoking status, meat, dairy products. | SUA |
Yuan 2000 [45] | Taiwan | NA | NA | 96 | Case–control | Never, ever | 288.1 (255.3–320.9) 200.0 (166.8–233.2) | Not mentioned | NA | SUA |
Haldar 2007 [50] | Northern Ireland | 18–64 | 31.5 | 89 | Cross-Sectional | Never, ever | Not mentioned | Green tea and black tea combined | Age, sex and BMI | SUA |
Choi 2007 [33] | USA | 54.0 | 100 | 45869 | Cohort | 0 cups/day <1 cups/day 1–3 cups/day ≥4 cups/day | 1.0 1.09 (0.92–1.30) 1.06 (0.85–1.33) 0.82 (0.38–1.75) | Not mentioned | Age, total energy intake, BMI, diuretic use, history of hypertension, history of renal failure, intake of alcohol, total meats, seafood, purine-rich vegetables, dairy foods, total vitamin C, decaffeinated coffee. | Gout (gout criteria of the American College of Rheumatology) |
Choi 2007 [34] | USA | 45.0 | 46.8 | 14314 | Cross-Sectional | SUA: 0 cups/day <1 cups/day 1–3 cups/day ≥4 cups/day HU: 0 cups/day <1 cups/day 1–3 cups/day ≥4 cups/day | 319.1 (317.6–320.6) 317.3 (315.5–319.0) 321.7 (317.3–326.2) 318.6 (312.8–324.4) 1.0 Not mentioned Not mentioned 1.00 (0.65–1.53) | Not mentioned | Age, sex, smoking status, BMI, smoking; use of diuretics, beta-blockers, allopurinol, uricosuric agents, hypertension, glomerular filtration rate, alcohol, total meats, seafood, dairy foods, decaffeinated coffee. | SUA HU (serum uric acid level >6.0 mg/dl) |
Choi 2010 [35] | USA | 46.0 | 0 | 89433 | Cohort | 0 cups/day <1 cups/day 1–3 cups/day ≥4 cups/day | 1.0 1.05 (0.86–1.28) 0.92 (0.74–1.16) 1.55 (0.98–2.47) | Not mentioned | Age, total energy intake, BMI, menopause, use of hormonal replacement, diuretic use, history of hypertension, intakes of alcohol, sugar-sweetened soft drinks, total meats, seafood, chocolate, dairy foods, total vitamin C, decaffeinated coffee. | Gout (gout criteria of the American College of Rheumatology) |
Yu 2010 [51] | China | 40.2 | 48.4 | 7403 | Cross-Sectional | Never, ever | 1.0 0.84 (0.82–0.86) | Not mentioned | NA | HU (serum uric acid >7.0 mg/dl in males and >6.0 mg/dl in females) |
Chang 2012 [47] | Taiwan | 75 | 100 | 361 | Cross-Sectional | Never, ever | Not mentioned | Not mentioned | NA | SUA |
Teng 2013 [36] | Singapore | 57.6 | 44.3 | 483 | Cross-Sectional | SUA (Green tea): Non-drinkers, Monthly drinkers, Weekly drinkers, Daily drinkers. SUA (Black tea): Non-drinkers, Monthly drinkers, Weekly drinkers, Daily drinkers. HU (Green tea): Non-drinkers, Monthly drinkers, Weekly drinkers, Daily drinkers. HU (Black tea): Non-drinkers, Monthly drinkers, Weekly drinkers, Daily drinkers. | 309.5 (298.4-321.0) 309.5 (290.4–329.9) 311.6 (296.3–327.7) 334.5 (316.2–353.9) 312.4 (301.4–323.8) 308.8 (289.0–329.9) 314.3 (298.6–330.7) 318.4 (299.6–338.4) 1.0 0.84 (0.36–1.98) 1.15 (0.62–2.14) 2.12 (1.03–4.36) 1.0 0.68 (0.28–1.67) 1.27 (0.68–2.37) 0.56 (0.25–1.27) | Green tea, black tea | Cholesterol, creatinine, HbA1c, triglycerides, age, gender, BMI, education, cigarette smoking status, physical activity status, hypertension at baseline, dairy products, red meat, fish, alcohol, soda, fruit juice. | SUA HU (serum uric acid level >6 mg/dl) |
Chatzistamatiou 2015 [49] | Greece | 51 | 53 | 660 | Cross-Sectional | Never, ever | Not mentioned | Not mentioned | NA | HU (serum uric acid >7.2Â mg/dl in males and >6.1Â mg/dl in females) |
Bae 2015 [37] | Korea | 61.9 | 37.9 | 9400 | Cross-Sectional | SUA (Male): <0.1 ml/day, 0.1–8.0 ml/day, 8.1–51.4 ml/day, ≥51.5 ml/day; SUA (Female): <0.1 ml/day, 0.1–8.0 ml/day, 8.1–51.4 ml/day, ≥51.5 ml/day; HU (Male): <0.1 ml/day, 0.1–4.0 ml/day, 4.1–25.7 ml/day, ≥51.5 ml/day; HU (Female): <0.1 ml/day, 0.1–4.0 ml/day, 4.1–25.7 ml/day, ≥51.5 ml/day; | 345.0 (340.9-349.1) 336.9 (328.6–345.8) 338.7 (332.1–344.0) 348.1 (341.5–354.7) 260.6 (258.2–263.0) 262.0 (254.8–269.0) 261.3 (257.7–264.9) 263.6 (259.4–267.8) 1.0 0.92 (0.66–1.28) 0.95 (0.73–1.22) 1.27 (0.96–1.67) 1.0 0.97 (0.66–1.42) 0.84 (0.62–1.14) 1.13 (0.81–1.59) | Not mentioned | Age, education, marital status, cigarette smoking, alcohol drinking, regular exercise, BMI, triglyceride, fasting serum glucose, hypertension medication, glomerular filtration rate, total energy, vitamin c, meat intake, seafood intake, dairy food intake, soft drink intake, added sugar in coffee, added cream in coffee. | SUA HU (serum uric acid >7.0 mg/dl in males and >6.0 mg/dl in females) |
Li 2015 [38] | China | 37.7 | 52.5 | 1372 | Cross-sectional | <1 time/week 1–6 times/week ≥6 times/week | 1.0 0.74 (0.47–1.17) 0.56 (0.33–0.93) | Not mentioned | Age, smoking and drinking status | HU (SUA >416 μmol/L in males and >357 μmol/L in females) |
Tian 2016 [46] | China | 63 | 44.1 | 19471 | Cohort study | Never, ever | 280.0 (278.6–281.3) 301.1 (299.2–303.0) | Green tea | Age, sex, BMI, education, smoking status, alcohol, drinking status, physical activity, hypertension status, hyperlipidemia status, diabetes status and family history of CHD | SUA |