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. 2016 Mar 21;31(9):811–851. doi: 10.1007/s10654-016-0138-6

Table 3.

Characteristics of meta-analyses investigating association between bladder cancer risk and various factors

References Risk factor (s) Primary studies included on bladder cancer in publication Comparison Selected as best estimate Risk estimates Number of primary studies included Adjustment level Heterogeneity Publication bias (Egger test)
Dietary factors
Yao et al. [19] Fruit, vegetables 20 CC
11 COH		 Fruit and vegetables; high versus low Yes RR 0.81; 95 % CI 0.67–0.99 10 Smoking I2 = 58.4 %
Fruit; high versus low Yes RR 0.77; 95 % CI 0.69–0.87 27 Smoking I2 = 54.9 % Egger p = 0.003
Vegetables; high versus low Yes (MMA) RR 0.81; 95 % CI 0.70–0.93 21 Smoking I2 = 66.0 % Egger p = 0.389
Citrus Fruits; high versus low No RR 0.79; 95 % CI 0.68–0.91 11 I2 = 53.2 % Egger p = 0.034
Cruciferous vegetables; high versus low Yes RR 0.84; 95 % CI 0.77–0.91 11 I2 = 30.7 % Egger p = 0.443
Steinmaus et al. [21] Fruit (low intake) 38 CC and COH Fruits; low versus high No RR 1.47; 95 % CI 1.25–1.74 8 Smoking X2 p = 0.99$
Vegetables (low intake) Vegetables; low versus high Yes (MMA) RR 1.15; 95 % CI 0.98–1.35 8 Smoking X2 p = 0.82$
Meat High versus low No RR 0.96; 95 % CI 0.73–1.27 4 Smoking X2 p = 0.97$
Vitamin A Retinol; low versus high intake No RR 1.01; 95 % CI 0.90–1.14 8 X2 p = 0.99$
Carotinoids Carotenoids; low versus high intake No RR 1.10; 95 % CI 0.99–1.22 3 X2 p = 0.99$
Vieira et al. [122] Fruit, Vegetables 15 COH Fruit and vegetables; high versus low No RR 0.89; 95 % CI 0.75–1.05 8 I2 = 33.8 %
Fruit; high versus low No RRs = 0.91; 95 % CI 0.82–1.00 11 Smoking I2 = 11.0 % Egger p = 0.48
Vegetables; high versus low No RRs = 0.92; 95 % CI 0.84–1.01 9 Smoking I2 = 5.0 % Egger p = 0.02
Citrus fruit; high versus low No RRs = 0.88; 95 % CI 0.77–1.01 6 Smoking I2 = 0.0 % Egger p = 0.38
Cruciferous vegetables; high versus low No RRs = 0.85; 95 % CI 0.69–1.06 6 Smoking I2 = 62.6 % Egger p = 0.5
Liu et al. [123] Fruit, vegetables 15 CC
12 COH		 Fruit and vegetables; high versus low No RR 0.83; 95 % CI 0.69–1.01 9 I2 = 57.0 %
Fruit; high versus low No RR 0.81; 95 % CI 0.73–0.89 27 I2 = 53.7 % Egger p = 0.052
Vegetables; high versus low No RR 0.84; 95 % CI 0.72–0.96 24 I2 = 76.3 % Egger p = 0.74
Xu et al. [124] Fruit, vegetables 14 COH Fruit and vegetables; every 0.2 serving increment per day No RR 1.00; 95 % CI 0.99–1.00 8 I2 = 38.5 %
Fruit; every 0.2 serving increment per day No RRs = 1.00; 95 % CI 0.99–1.00 14 Smoking I2 = 45.8 % Egger p < 0.01
Vegetables; every 0.2 serving increment per day No RRs = 1.00; 95 % CI 0.99–1.00 14 Smoking I2 = 19.0 % Egger p = 0.93
Citrus fruit; every 0.2 serving increment per day No RRs = 1.00; 95 % CI 1.00–1.00 7 I2 = 0.0 %
Cruciferous vegetables; every 0.2 serving increment per day No RRs = 0.97; 95 % CI 0.93–1.01 8 I2 = 55.8 %
Liang et al. [20] Citrus fruits 8 CC
6 COH		 Citrus fruits; high versus low Yes RR 0.85; 95 % CI 0.76–0.94 14 I2 = 72.1 % Egger p = 0.004
6 COH Citrus fruits; high versus low No RR 0.96; 95 % CI 0.87–1.07 6 I2 = 19.8 %
8 CC Citrus fruits; high versus low No RR 0.77; 95 % CI 0.64–0.92 8 I2 = 68.7 %
Liu et al. [121] Cruciferous vegetables 5 CC
5 COH		 Cruciferous vegetables; high versus low No RR 0.80; 95 % CI 0.69–0.92 10 I2 = 45.9 % Egger p = 0.51
5 COH Cruciferous vegetables; high versus low No Cohort: RR 0.86; 95 % CI 0.61–1.11 5 I2 = 73 %
5 CC Cruciferous vegetables; high versus low No CC: RR 0.78; 95 % CI 0.67–0.89 5 I2 = 0.0 %
Bai et al. [22] Total fluid intake 17 CC
4 COH		 High versus low Yes RRm = 1.12; 95 % CI 0.94–1.33 14 Most adjusted I2 = 82.8 % Egger p = 0.059
Isa (submitted) Total fluid intake 15 CC
3 COH		 250 ml/day increment No RR 1.02; 95 % CI 1.00–1.04 15 Egger p = 0.614
Zhang et al. [126] Tea 7 COH All tea; high versus low No RR 0.92; 95 % CI 0.76–1.13 7 I2 = 23.8 %
All tea; one cup/day increment No RR 0.98; 95 % CI 0.93–1.02 7 I2 = 44.1 %
Green tea; one cup/day increment No RR 1.02; 95 % CI 0.95–1.11 3 I2 = 63.9 %
Black tea; one cup/day increment No RR 0.73; 95 % CI 0.33–1.60 1
Wu et al. [127] Tea 12 CC
3 COH		 All tea; high versus low No RRm = 1.01; 95 % CI 0.80–1.29 7 Most adjusted Egger p = 0.88
Green tea; high versus low No RR 1.03; 95 % CI 0.82–1.31 5 I2 = 0.0 % Egger p = 0.49
Black tea; high versus low No RR 0.84; 95 % CI 0.7–1.01 6 I2 = 0.0 % Egger p = 1.0
Wang et al. [128] Tea 13 CC
4 COH		 All tea; high versus low No RRm = 1.12; 95 % CI 0.88–1.43; I2 = 64.6 %; n = 17 17 Most adjusted Egger p = 0.298
Green tea; high versus low No RR 0.81; 95 % CI 0.68–0.98 4 I2 = 0.0 % Egger p = 0.73
Black tea; high versus low No RR 1.05; 95 % CI 0.83–1.32 5 I2 = 49.4 % Egger p = 0.41
Qin et al. [130] Tea 17 CC
6 COH		 All tea; high versus low Yes RR 0.94; 95 % CI 0.85–1.04 23 I2 = 28.3 % Egger p = 0.52
Green tea; high versus low No RR 0.97; 95 % CI 0.73–1.21; 5 I2 = 0.0 % Egger p = 0.38
Black tea; high versus low No RR 0.79; 95 % CI 0.59–0.99 7 I2 = 33.1 % Egger p = 0.38
Huang et al. [24] Coffee 5 COH High versus none/low No RR 1.08; 95 % CI 0.71–1.66 5 I2 = 62.9 %
Zhou et al. [25] Coffee 20 CC
5 COH		 High (>5–6 cups/day) versus none No Case–control: RRs = 1.45; 95 % CI 1.29–1.63
This category was not calculated for cohort studies		 20 I2 = 31.8 % No publication bias (no test estimate reported)
Sala et al. [28] Coffee Pooled analysis of 10 CC 6–9 cups versus none No RRm = 1.0; 95 % CI 0.6–1.4 Most adjusted, analysis restricted to non-smokers
≥10 cups versus none No RRm = 1.8; 95 % CI 1.0–3.3 Most adjusted, analysis restricted to non-smokers
Villanueva et al. [27] Coffee Pooled analysis of 6 CC >5 cups/day versus ≤5 cups/day; overall Yes (MMA) RRms = 1.25; 95 % CI 1.08–1.44 6 Most adjusted, incl. smoking
>5 cups/day versus ≤5 cups/day; men only No RRms = 1.23; 95 % CI 1.05–1.44 5 Most adjusted, incl. smoking
>5 cups/day versus ≤5 cups/day; women only No RRms = 1.31; 95 % CI 0.99–1.74 5 Most adjusted, incl. smoking
1 l/day increment No RRms = 1.24; 95 % CI 1.08–1.43 6 Most adjusted, incl. smoking
Yu et al. [26] Coffee 9 COH Drinkers versus none/lowest Yes (MMA) RR 0.83; 95 % CI 0.73–0.94 9 I2 = 39.3 % Egger p = 0.793
Wu et al. [29] Coffee 34 CC
6 COH		 High versus low Yes (MMA) RRms = 1.28; 95 % CI 1.21–1.46 18 Most adjusted, incl. smoking I2 = 28.5 Egger p = 0.051
Boyle et al. [30] Sweetened carbonated beverages 5 studies High versus low Yes RR 1.13; 95 % CI 0.89–1.45 5 I2 = 0.0 % Egger p = 0.05
Li et al. [135] Milk
Dairy products		 12 CC
6 COH		 Milk; high versus low Yes RRm = 0.91; 95 % CI 0.72–1.15 7 Most adjusted Q p = 0.020 Egger p = 0.048
Dairy products; high versus low Yes RRm = 1.01; 95 % CI 0.86–1.19 3 Most adjusted Q p = 0.108 Egger p = 0.73
Mao et al. [31] Milk and Dairy products 8 HCC
5 PCC
6 COH		 All milk; high versus low No RRms = 0.84; 95 % CI 0.72–0.97 16 Most adjusted, incl. smoking I2 = 70.1 % Egger p = 0.055
Whole milk; high versus low No RR 2.23; 95 % CI 1.45–3.00 2 I2 = 0
Skim milk; high versus low No RR 0.47; 95 % CI 0.18–0.79 2 I2 = 0
Fermented milk; high versus low No RR 0.69; 95 % CI 0.47–0.91 5 I2 = 62.5 %
Li et al. [32] Fish 6 HCC
3 PCC
5 COH		 High versus low Yes RRs = 0.86; 95 % CI 0.61–1.12; I2 = 85.4 %; n = 14; Begg’s p = 0.101 14 Smoking
Li et al. [33] Meat 9 CC
5 COH		 Red meat; high versus low Yes RR 1.15; 95 % CI 0.97–1.36 14 I2 = 73.5 % Egger p = 0.83
6 CC
5 COH		 Processed meat; high versus low Yes RR 1.22; 95 % CI 1.04–1.43 11 I2 = 64.9 % Egger p = 0.35
Pelucchi et al. [34] Alcohol 14 CC
2 NCC
3 COH		 Heavy intake, ≥ 3 drinks (≥ 37.5 g)/day versus non-drinkers Yes RR 0.97; 95 % CI 0.72–1.31 7 Smoking X2 p < 0.01
Moderate intake, <3 drinks/day versus non-drinkers No RR 0.98; 95 % CI 0.89–1.07 15 Smoking X2 p = 0.05
Bagnardi et al. [139] Alcohol 9 CC
2 COH		 Highest category (100 g/day) versus non-drinkers No RR 1.17; 95 % CI: 0.97–1.41 11 Het. p = N.S.
Highest category (100 g/day) versus non-drinkers No RRs = 1.09; 95 % CI: 0.89–1.33 Smoking Het. p < 0.05
Zeegers et al. [140] Alcohol 6 studies Current alcohol use versus non-use No RR 1.3; 95 % CI 1.1–1.5 6
Li et al. [35] Egg 9 CC
4 COH		 All eggs; high versus low Yes RRm = 1.11; 95 % CI 0.73–1.69 6 Most adjusted I2 = 75.8 % Egger p = 0.55
Fried eggs; high versus low No RR 2.04; 95 % CI 1.41–2.95 2 I2 = 0.0 %
Boiled eggs; high versus low No RR 1.25; 95 % CI 0.82–1.91 2 I2 = 35.5 %
Pelucchi et al. [45] Dietary acrylamide 1 CC
1 COH
1 C-COH		 High versus low Yes RR 0.93; 95 % CI 0.78–1.11 3 X2 p = 0.91
10 mg/day increase in intake No RR 1.00; 95 % CI 0.96–1.03 3 X2 p = 0.97
Tang et al. [36] Vitamin A (total) 14 CC
11 COH		 Supplement, diet and blood levels; high versus low Yes RRms = 0.82; 95 % CI 0.65–0.95 11 Most adjusted, incl. smoking I2 = 46.3 % Egger p = 0.057
Dietary intake; high versus low No RRms = 0.90; 95 % CI 0.80–1.01 Most adjusted, incl. smoking I2 = 0 %
Supplementation versus placebo or no supplementation Yes RRms = 0.64; 95 % CI 0.47–0.82 Most adjusted, incl. smoking I2 = 0 %
Jeon et al. [37] Beta-carotene supplements 2 RCT Supplementation versus placebo or no supplementation No RR 1.52; 95 % CI 1.03–2.24 2 I2 = 0.0 %
Liao et al. [39] Vitamin D 1 CC
2 NCC
2 COH		 Serum levels; high versus low Yes RRs = 0.75; 95 % CI 0.65–0.87 5 Smoking I2 = 0.0 % Egger p = 0.57
Chen et al. [40] Vitamin D 1 CC
3 COH		 Circulating levels; high versus low No RR 0.75; 95 % CI 0.57–0.99 4 I2 = 51.7 % Egger p = 0.87
3 studies Diet and supplement; high versus low No RR 0.92; 95 % CI 0.66–1.28 3 I2 = 32.3 % Egger p = 0.41
Vitamin E 4 CC
5 COH		 Diet; high versus low No RRm = 0.69; 95 % CI 0.52–0.92 5 I2 = 47.1 % Egger p = 0.01
3 CC
3 COH		 Diet and supplement; high versus low No RRm = 0.76; 95 % CI 0.56–1.02 5 I2 = 49.8 % Egger p = 0.35
1 CC
6 COH		 Supplementation versus placebo or no supplementation No RRm = 0.64; 95 % CI 0.48–0.85 I2 = 0.6 % Egger p = 0.39
Vitamin C 7 CC
7 COH		 Diet; High versus Low No RRm = 0.69; 95 % CI 0.58–0.82 6 I2 = 13.7 % Egger p = 0.28
5 CC
3 COH		 Diet and supplement; high versus low No RRm = 0.80; 95 % CI 0.62–1.03 5 I2 = 33.4 % Egger p = 0.03
6 CC
3 COH		 Supplementation versus placebo or no supplementation No RRm = 0.84; 95 % CI 0.55–1.29 4 I2 = 74.4 % Egger p = 0.002
Wang et al. [38] Vitamin C 11 CC
9 COH		 Intake; high versus low Yes RRs = 0.90; 95 % CI 0.79–1.00 20 Smoking I2 = 43.7 % Egger p = 0.064
Vitamin E 7 CC
8 COH		 Intake; high versus low Yes RRs = 0.82; 95 % CI 0.74–0.90 15 Smoking I2 = 0 % Egger p = 0.534
He et al. [41] Folate 6 CC
7 COH		 Intake; high versus low Yes RR 0.84; 95 % CI 0.72–0.96 13 I2 = 28.9 % Egger p = 0.06
Myung et al. [37] Antioxidant supplement 4 RCT Supplementation versus placebo or no supplementation No RR 1.52; 95 % CI 1.06–2.17 4 I2 = 0.0 %
Amaral et al. [42] Selenium 3 CC
3 NCC
1 C-COH		 Serum and toenail levels; high versus low Yes OR = 0.61; 95 % CI 0.42–0.87 7 I2 = 60.8 % Egger p = 0.357
Vinceti et al. [43] (Cochrane SR) Selenium 5 prospective studies Serum, toenail or plasma levels; high versus low No OR = 0.67; 95 % CI 0.46–0.97 5 I2 = 30 %
2 RCT Supplementation versus Placebo Yes RR 1.14; 95 % CI 0.81–1.61 2 I2 = 0.0 %
Sun et al. [46] Obesity 15 COH Obese versus normal weight Yes RRs = 1.10; 95 % CI 1.03–1.18 12 Smoking I2 = 8.8 % Egger p = 0.712
Pre-obese versus normal weight Yes RRs = 1.07; 95 % CI 0.99–1.16 13 Smoking I2 = 46.1 % Egger p = 0.712
Qin et al. [47] Obesity 11 COH Obese versus normal weight No RRs = 1.09; 95 % CI 1.01–1.17 9 Smoking I2 = 35.9 % Egger p = 0.244
Behavioural factors
Hemelt et al. [11] Smoking 21 CC
11 COH
2 NCC		 All tobacco; Ever smokers versus never smokers No RR 2.25; 95 % CI 1.96–2.59 15
All tobacco; Ex smokers versus never smokers No RR 1.90; 95 % CI 1.71–2.11 8
All tobacco; Current smokers versus never smokers No RR 3.35; 95 % CI 2.90–3.88 11
Cigarettes; Ever smokers versus never smokers No RR 2.24; 95 % CI 1.81–2.78 9
Cigarettes; Ex smokers versus never smokers No RR 1.95; 95 % CI 1.55–2.47 4
Cigarettes; Current smokers versus never smokers No RR 3.13; 95 % CI 2.33–4.21 6
Puente et al. [48] Smoking Pooled analysis of 14 CC Current smokers versus never smokers; Male No RR 3.89; 95 % CI 3.53–4.29
Current smokers versus never smokers; Female No RR 3.55; 95 % CI 3.06–4.10
Ex-smokers versus never smokers; Male No RR 2.21; 95 % CI 2.01–2.43
Ex-smokers versus never smokers; Female No RR 2.21; 95 % CI 1.87–2.61
Freedman et al. [49] Smoking 7 COH Current smokers versus never smokers No RR 2.94; 95 % CI 2.45–3.54 7 I2 = 0.0 % Egger p = 0.32
Brennan et al. [50] Smoking Pooled analysis of 11 CC (men only) Ever-smokers versus never smokers No RR 3.63; 95 % CI 3.13–4.20
Current smokers versus never and ex-smokers No RR 2.47; 95 % CI 2.23–2.74
Brennan et al. [51] Smoking Pooled analysis of 11 CC (women only) Ever-smokers versus never smokers No RR 3.1; 95 % CI 2.5–3.9
Current smokers versus never and ex-smokers No RR 2.9; 95 % CI 2.3–3.7
Van Osch et al. submitted [10] Active smoking 18 COH
71 CC		 Active smoking; Ex-smokers versus never smokers Yes RR 1.83; 95 % CI 1.52–2.14 12 Age, sex Egger p = 0.150
Active smoking; Current smokers versus never smokers Yes RR 3.14; 95 % CI 2.53–3.75 13 Age, sex
Active smoking; ≤20 versus >20 years at first exposure No RR 1.33; 95 % CI 0.92–1.74 4
Cumberbatch et al. [53] Active smoking Ex-smokers versus never smokers No RR 3.37; 95 % CI 3.01–3.78 48 Most adjusted estimates in MA I2 = 82.2 % Egger p = 0.13
Begg p = 0.03
Current smokers versus never smokers No RR 1.98; 95 % CI 1.76–2.22 49 Most adjusted estimates in MA I2 = 78.6 %
Pipe; Smokers versus never smokers No RR 1.49; 95 % CI 1.18–1.88 4 I2 = 39.4 %
Cigar; Smokers versus never smokers No RR 1.62; 95 % CI 1.18–2.22 4 I2 = 0.0 %
Smokeless tobacco Snuff; users versus non-users No RR 0.89; 95 % CI 0.56–1.42 2 I2 = 23.7 %
Chewing tobacco; users versus non-users No RR 1.04; 95 % CI 0.75–1.45 2 I2 = 0.0 %
Pitard et al. [52] Active smoking Pooled analysis of 6 CC (men only) Pipe only; Smokers versus never smokers Yes RR 1.9; 95 % CI 1.2–3.1
Cigar only; Smokers versus never smokers Yes RR 2.3; 95 % CI 1.6–3.5
Cigarette only; Smokers versus never smokers No RR 3.5; 95 % CI 2.9–4.2
Van Hemelrijck et al. [54] Passive smoking 5 CC
3 COH		 Exposed versus not exposed Yes RR 0.99; 95 % CI 0.86–1.14 8 Non-smokers only I2 = 35.6 % Begg p = 0.32
Lee et al. [55] Smokeless tobacco 12 CC
1 COH		 Smokeless tobacco use versus never use Yes RRs = 0.95; 95 % CI 0.71–1.29 9 Smoking I2 = 59.6 %
Keimling et al. [56] Physical activity 4 CC
11 COH		 High versus low Yes RRm = 0.86; 95 % CI 0.77–0.95 7 Most adjusted I2 = 0.0 %
Turati et al. [57] Personal hair dye 15 CC
2 COH		 Personal use of any type of hair dyes versus no use Yes RRs = 0.94; 95 % CI 0.82–1.08 12 Smoking I2 = 49.9 % Egger p = 0.54
Occupational (Comparing the specific occupation versus any other occupation or the general population)
Guha et al. [158] Painters 30 CC
2 COH
9 RL		 Painters No RR 1.25; 95 % CI 1.16–1.34 41 I2 = 23.5 %
Painters No RRs = 1.28; 95 % CI 1.15–1.43 Smoking I2 = 0.7 %
Painters No RRms = 1.27; 95 % CI 0.99–1.63 Most adjusted, incl. smoking I2 = 0.1 %
Bachand et al. [159] Painters 33 CC Painters No RR 1.30; 95 % CI 1.17–1.44 33 Smoking; morbidity and mortality combined
4 COH Painters No RR 1.23; 95 % CI 0.95–1.59 4 Smoking; morbidity only
Harling et al. [161] Hairdressers 28 CC
14 RCOH		 Hairdressers No RR 1.35; 95 % CI 1.13–1.61 23 Smoking X2 p = 0.19
Hairdressers; job held ≥ 10 years No RR 1.70; 95 % CI 1.01–2.88 6 X2 p = 0.46
Takkouche et al. [160] Hairdressers 26 CC
8 COH		 Hairdressers No RR 1.33; 95 % CI 1.07–1.67 19 Smoking Q p = 0.77
Hairdressers No RR 1.35; 95 % CI 1.21–1.50 26 Incidence only Q p = 0.78
‘t Mannetje et al. [162] Sales workers 10 CC
2 RL
3 mortality studies		 Sales workers; Men No RR 1.04; 95 % CI 0.97–1.12 Smoking, incidence only Q p = 0.3 Egger p = 0.4
Sales workers; Women No RR 1.22; 95 % CI 1.06–1.41 Smoking, incidence only Q p = 0.44 Egger p < 0.01
Manju L et al. [164] Motor vehicle driving 3 COH Overall (motor vehicle drivers and railroad workers) No RR 1.08; 95 % CI 1.00–1.17 3 Het. p = 0.85
27 CC Truck drivers No RR 1.18; 95 % CI 1.09–1.28 18 Het. p = 0.25
27 CC Bus drivers No RR 1.23; 95 % CI 1.06–1.44 11 Het. p = 0.19
Boffetta and Silverman [163] Motor vehicle driving 16 CC
7 COH
6 routinely collected data
(men only)		 Truck drivers No RR 1.17; 95 % CI 1.06–1.29 15 Het. p = 0.3 Egger p = 0.07
Bus drivers No RR 1.33; 95 % CI 1.22–1.45 10 Het. p = 0.4 Egger p = 0.001
Acquavella et al. [165] Farmers 10 Follow-up studies
8 CC
11 PMR
(men only)		 Farmers No RR 0.79; 95 % CI 0.72–0.86 29 X2 p < 1*10−5
10 Follow-up studies Farmers No RR 0.62; 95 % CI 0.59–0.65 10 X2 p = 0.08
8 CC Farmers No RR 0.94; 95 % CI 0.86–1.04 8 X2 p = 0.09
Gaertner et al. [166] Foundry workers 22 CC
9 COH
14 surveillance studies		 Foundry workers No RR 1.11; 95 % CI 0.96–1.29 16 (CC only) Smoking X2 p = 0.07 (15df)
Foundry workers No RR 1.14; 95 % CI 1.04–1.26; 11 Incidence only X2 p = 0.28 (10df)
Mastrangelo et al. [167] Textile workers Unknown Spinners No RR 1.19; 95 % CI 0.80–1.57 2 X2 p < 0.001$
Weavers No RR 2.40; 95 % CI 1.62–3.18 2 X2 p = 0.001$
Dyers No RR 1.39; 95 % CI 1.07–1.71 3 X2 p = 0.505$
Tokumaru et al. [168] Flight attendants 3 COH (female only) Flight attendants No RR 2.03; 95 % CI 0.75–5.43 3 Incidence only Q p = N.S.
Buja et al. [169] Flight attendants 4 COH (female only) Flight attendants No RR 1.45; 95 % CI 0.33–3.16 4 Incidence only Tau = 0.39
Baena et al. [171] Petroleum industry 8 CC Petroleum industry workers No RR 1.5; 95 % CI 1.29–1.75 8
Greenberg et al. [172] Chemical workers 19 COH for incidence Chemical workers No RR 2.21; 95 % CI 1.18–4.15 19 Incidence only
Vlaanderen et al. [173] Dry cleaning 4 CC
3 COH		 Dry cleaning workers No RR 1.47; 95 % CI 1.16–1.85 7 I2 = 0 % Egger p > 0.05
Fu et al. [174] Inorganic lead compounds 5 studies Exposed to inorganic lead compounds versus non-exposed No RR 1.41; 95 % CI 1.16–1.71 5 Hom. p > 0.30
Collins et al. [176] Acrylonitrile workers 10 studies Acrylonitrile workers No RR 0.8; 95 % CI 0.3–2.2 3 Incidence Het. p = 0.49
Rota et al. [179] Polycyclic aromatic hydrocarbons (PAHs) 13 COH Aluminium production workers No RR 1.28; 95 % CI 0.98–1.68 10 X2 p = 0.002 Egger p = 0.22
Asphalt workers No RR 1.03; 95 % CI 0.82–1.30 2 X2 p = 0.31
Carbon black production No RR 1.10; 95 % CI 0.61–2.00 3 X2 p = 0.29 Egger p = 0.61
Workers in iron and steel foundry No RR 1.38; 95 % CI 1.00–1.91 9 X2 p = 0.001 Egger p = 0.3

95 % CI 95 % confidence interval, CC case–control study, C-COH case-cohort study, COH cohort study, df degrees of freedom, ECO ecological study, HCC hospital-based case–Control study, Het. heterogeneity, Hom. homogeneity, NCC nested case–control study, N.S. not significant, OR odds ratio, PCC population-based case–control study, PCOH prospective cohort study, PMR proportional mortality ratio, RCOH retrospective cohort study, RE risk estimate, RCT randomised controlled trial, RL record linkage study, RR relative risk, SIR standardised incidence ratio

$The p value was calculated by the authors of the current article when only the X 2 statistic and degrees of freedom were presented