Background
Methods
Data sources, search strategy, and selection criteria
Data collection and quality assessment
Statistical analysis
Results
Literature search
Study | Publication year | Study design | Country | Sample size | Percent of male (%) | Mean age (years) | Number of cases | DR diagnosis | DR definition | Diabetes | Exposure Definition | Adjustment/matched | NOS score |
---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Young [28] | 1984 | Cohort | UK | 296 | 100.0 | 20.0–59.0 | 66 | Fundoscopic | Four Grades | Mixed | ≤10 measures/ week, > 10 measures/week | Crude | 6 |
Moss [29] | 1994 | Cohort | USA | 916 | NA | ≥ 21.0 | 238 | Fundus photographs | ETDRS | Mixed | Average loz/ day increase | Age, sex, HbA1c, retinopathy | 8 |
Kohner [30] | 1998 | Case control | UK | 2964 | 58.4 | 25.0–65.0 | 1102 | Retinal photography | ETDRS | T2DM | None, occasional, regular, heavy | Crude | 6 |
Rasmidatta [31] | 1998 | Case control | Thailand | 198 | NA | 60.5 | 63 | Fundoscopic examinations | Three grades | T2DM | Nondrinker, drinker, not regular drinker | HbA1c, cholesterol, triglyceride, HDL, BP | 6 |
Giuffrè [32] | 2004 | Case control | Italy | 132 | 38.6 | ≥ 40.0 | 45 | Fundus examination | ETDRS | Mixed | None, 1–19 years, 20 years or more | Crude | 6 |
Hirai [33] | 2007 | Cross-sectional | USA | 537 | 50.1 | 45.3 | 309 | Retinal photography | ETDRS | T1DM | Alcohol/No alcohol | Crude | 4 |
Beulens [34] | 2008 | Cross-sectional | Europe | 3250 | 29.7 | 15.0–60.0 | 304 | Retinal photographs | Three grades | T1DM | 0 g/week, 0.0–4.9 g/week, 5.0–29.9 g/ week, 30.0–69.9 g/week, 70.0–209.9 g/week, ≥210 g/week | Age, sex, centre, duration of illness, systolic BP, physical activity, smoking, BMI, presence of cardiovascular disease and HbA1c | 7 |
Xu [35] | 2009 | Cohort | China | 4141 | 43.4 | ≥ 40.0 | 366 | Fundus photographs | NA | General | Consumers, non-consumers | BMI, HDL, LDL, arterial hypertension | 7 |
Lee [36] | 2010 | Cohort | 14 countries | 1239 | 60.7 | 55.0–81.0 | 640 | Retinal photography | ETDRS | T2DM | 0, drinks /week 1–14, drinks/week > 14 drinks /week | Age, sex, HbA1c, systolic BP, duration of diabetes, BMI, cigarette smoking, ethnicity | 8 |
Yang [37] | 2013 | Cross-sectional | Korea | 978 | 54.1 | ≥ 19.0 | 112 | Fundus examination | ETDRS | Mixed | ≥4 alcoholic drinks/week, < 3 drinks/week | Age, gender, smoking status, regular exercise, BMI, serum total cholesterol, serum triglyceride, serum HDL cholesterol, anti-lipid drug use | 6 |
Jongsareejit [38] | 2013 | Cross-sectional | Thailand | 933 | NA | 59.5 | 214 | Indirect ophthalmoscope | International scales | T2DM | No, ever, current | Gender, age, diastolic BP, waist, total cholesterol, HDL, ccular perfusion pressure | 5 |
Harjutsalo [39] | 2014 | Cross-sectional | Finland | 3608 | 52.6 | 28.9–46.8 | 1191 | Retinal photography | NA | T1DM | Heavy drinker light drinker | Crude | 3 |
Fenwick [40] | 2015 | Cross-sectional | Australia | 395 | 64.1 | ≥ 18.0 | 235 | Fundus photography | ETDRS | T2DM | None, moderate, high | Education, income, language spoken at home, country of birth, lipid lowering drugs, hypertension drugs | 6 |
Tseng [41] | 2015 | Cohort | China | 573 | 61.8 | 58.9 | 91 | Funduscopic | Three grades | T2DM | Drinker, no-drinker | Crude | 6 |
Martín-Merino [42] | 2016 | Case control | UK | 17,130 | 55.9 | All stages | 7735 | Computerized records | NA | T2DM | 0–1 units/week 2–21 units/ week 22–34 units/week ≥35 units/week | Sex, age at index date, diabetes duration, primary care practitioner visits, referrals and hospitalizations, smoking, first HbA1c; systolic BP, glaucoma; cataracts, or lens extraction, HDL and triglycerides, and hypoglycaemic agents, including oral hypoglycaemic drugs and insulin | 7 |
Study characteristics
Meta-analysis
Subgroup analysis
Study design | Factors | Group | OR and 95%CI | P value | Heterogeneity (%) | P value for Q test | P value between subgroups |
---|---|---|---|---|---|---|---|
Cohort studies | Countries | Western | 1.04 (0.70–1.53) | 0.855 | 50.5 | 0132 | 0.318 |
Eastern | 0.77 (0.30–2.03) | 0.603 | 73.9 | 0.050 | |||
Publication year | Before 2010 | 0.87 (0.42–1.80) | 0.703 | 75.3 | 0.018 | 0.722 | |
2010 or after | 0.96 (0.76–1.23) | 0.771 | 0.0 | 0.416 | |||
Population | T2DM | 0.96 (0.76–1.23) | 0.771 | 0.0 | 0.416 | 0.086 | |
Mixed | 1.15 (0.52–2.54) | 0.722 | 69.7 | 0.069 | |||
General | 0.48 (0.25–0.93) | 0.030 | – | – | |||
Adjusted status | Yes | 0.77 (0.53–1.11) | 0.162 | 41.3 | 0.182 | 0.024 | |
No | 1.52 (0.96–2.42) | 0.076 | 0.0 | 0.540 | |||
Study quality | High | 0.77 (0.53–1.11) | 0.162 | 41.3 | 0.182 | 0.024 | |
Low | 1.52 (0.96–2.42) | 0.076 | 0.0 | 0.540 | |||
Case control studies | Countries | Western | 0.97 (0.75–1.24) | 0.792 | 76.5 | 0.014 | 0.729 |
Eastern | 0.88 (0.26–2.95) | 0.836 | – | – | |||
Publication year | Before 2010 | 0.71 (0.36–1.41) | 0.332 | 64.9 | 0.058 | 0.086 | |
2010 or after | 1.11 (1.04–1.18) | 0.001 | – | – | |||
Population | T2DM | 1.10 (1.03–1.16) | 0.003 | 0.0 | 0.490 | 0.007 | |
Mixed | 0.36 (0.16–0.81) | 0.014 | – | – | |||
Adjusted status | Yes | 1.11 (1.04–1.18) | 0.001 | 0.0 | 0.707 | 0.093 | |
No | 0.65 (0.24–1.72) | 0.383 | 82.4 | 0.017 | |||
Study quality | High | 1.11 (1.04–1.18) | 0.001 | – | – | 0.086 | |
Low | 0.71 (0.36–1.41) | 0.332 | 64.9 | 0.058 | |||
Cross-sectional studies | Countries | Western | 0.79 (0.61–1.03) | 0.080 | 46.9 | 0.130 | 0.088 |
Eastern | 1.11 (0.77–1.58) | 0.583 | 0.0 | 0.599 | |||
Publication year | Before 2010 | 0.85 (0.60–1.20) | 0.354 | 62.0 | 0.105 | 0.532 | |
2010 or after | 0.87 (0.61–1.24) | 0.451 | 48.4 | 0.121 | |||
Population | T1DM | 0.85 (0.67–1.08) | 0.187 | 33.5 | 0.223 | 0.896 | |
T2DM | 0.79 (0.36–1.77) | 0.573 | 82.2 | 0.018 | |||
Mixed | 0.96 (0.51–1.81) | 0.900 | – | – | |||
Adjusted status | Yes | 0.80 (0.59–1.10) | 0.170 | 54.4 | 0.087 | 0.144 | |
No | 1.01 (0.75–1.35) | 0.973 | 00 | 0.718 | |||
Study quality | High | 0.73 (0.58–0.91) | 0.006 | – | – | 0.114 | |
Low | 0.92 (0.70–1.20) | 0.538 | 36.9 | 0.175 |