TABLE 2.
Pooled risk estimates of bladder cancer risk associated with high versus low carotenoid intake and circulating carotenoid concentrations in adults as defined in each original study: overall and subgroup analysis1
| Test for heterogeneity of RRs | |||||||
|---|---|---|---|---|---|---|---|
| Factors stratified | Studies, n | Participants, n | RR (95% CI) | I2 Parameter, %2 | χ2 | P value | P 3 |
| Dietary intake | |||||||
| Total carotenoids | |||||||
| All studies | 11 | 366,246 | 0.88 (0.76, 1.03) | 74.5 | 39.26 | <0.0001 | |
| Sex | 0.84 | ||||||
| Men | 10 | 172,261 | 0.85 (0.72, 0.99) | 71.0 | 31.07 | <0.0001 | |
| Women | 6 | 193,985 | 0.86 (0.67, 1.09) | 79.6 | 24.47 | <0.0001 | |
| Study design | <0.0001 | ||||||
| Case-control | 7 | 12,925 | 0.77 (0.63, 0.94) | 64.7 | 16.98 | 0.009 | |
| Cohort | 4 | 353,321 | 1.09 (0.93, 1.27) | 56.8 | 6.95 | 0.074 | |
| Origin of the participants | 0.02 | ||||||
| Europeans | 3 | 32,410 | 1.05 (0.92, 1.20) | 39.7 | 3.32 | 0.19 | |
| Americans | 8 | 333,836 | 0.80 (0.64, 1.004) | 76.9 | 30.32 | <0.0001 | |
| Study quality | <0.0001 | ||||||
| 7 stars | 3 | 117,692 | 1.13 (0.95, 1.36) | 51.7 | 4.14 | 0.13 | |
| 8+ stars | 8 | 248,554 | 0.81 (0.68, 0.95) | 63.4 | 19.13 | 0.008 | |
| α-carotene | 9 | 364,699 | 0.94 (0.80, 1.09) | 46.1 | 16.71 | 0.053 | |
| β-carotene | 14 | 447,351 | 0.95 (0.88, 1.03) | 35.9 | 21.85 | 0.08 | |
| β-cryptoxanthin | 7 | 360,758 | 0.90 (0.80, 1.02) | 44.3 | 12.57 | 0.08 | |
| Lutein and zeaxanthin | 8 | 362,365 | 0.91 (0.76, 1.10) | 51.5 | 16.48 | 0.04 | |
| Lycopene | 8 | 362,365 | 0.99 (0.87, 1.12) | 13.2 | 9.22 | 0.32 | |
| Circulating carotenoid concentrations | |||||||
| Total carotenoids | 3 | 2014 | 0.36 (0.12, 1.07) | 85.2 | 13.48 | 0.001 | |
| α-carotene | 3 | 2191 | 0.52 (0.21, 1.27) | 67.1 | 6.08 | 0.048 | |
| β-carotene | 4 | 2296 | 0.67 (0.28, 1.62) | 74.0 | 11.53 | 0.009 | |
| β-cryptoxanthin | 3 | 2191 | 0.64 (0.22, 1.86) | 69.6 | 6.57 | 0.04 | |
| Lutein and zeaxanthin | 3 | 2191 | 0.53 (0.33, 0.84) | 34.0 | 6.06 | 0.19 | |
| Lycopene | 4 | 2296 | 0.76 (0.39, 1.49) | 49.0 | 5.88 | 0.12 | |
| Dietary supplementation | |||||||
| β-carotene | 2 | 132,607 | 0.94 (0.70, 1.26) | 0.0 | 0.1 | 0.75 | |
1
The associations of carotenoid intakes/circulating carotenoid concentrations with bladder cancer risk were estimated using DerSimonian and Laird random-effect (15) models by comparing the highest with the lowest (the referent) category.
2
Heterogeneity among studies was evaluated by the Cochran Q test (16, 17) and the I2 parameter, which represents the percentage of total variation across studies that is attributable to heterogeneity rather than chance (49).
3
P values test for the homogeneity comparison between subgroups.