Table 2.
Subgroup analysis results for DII and oral cancer risk.
| Subgroups | No. of studies | The highest DII vs. the lowest DII | Higher DII vs. lower DII | DII, per 1 unit | |||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Pooled OR (95% CI) | I 2 (%) | p a | p b | Pooled OR (95% CI) | I 2 (%) | p a | p b | Pooled OR (95% CI) | I 2 (%) | p a | p b | ||
| All studies | 5 | 2.35 (1.88, 2.94) | 8.1 | 0.360 | – | 1.79 (1.49, 2.15) | 0.0 | 0.614 | – | 1.17 (1.05, 1.30) | 86.1 | <0.001 | – |
| Region | 0.231 | 0.594 | 0.174 | ||||||||||
| Asia | 2 | 2.46 (1.76, 3.45) | 0.0 | 0.825 | 1.81 (1.40, 2.33) | 0.0 | 0.380 | 1.12 (0.94, 1.34) | 89.3 | 0.002 | |||
| Europe | 1 | 2.08 (1.47, 2.93) | – | – | 1.59 (1.07, 2.34) | – | – | 1.20 (1.11, 1.30) | – | – | |||
| North America | 1 | 2.47 (1.34, 4.75) | – | – | 1.87 (1.29, 2.71) | – | – | 1.14 (1.04, 1.24) | – | – | |||
| South America | 1 | 18.46 (2.28, 149.72) |
– | – | 5.43 (0.90, 32.65) |
– | – | 1.69 (1.18, 2.43) | – | – | |||
| Years of duration | 0.545 | 0.924 | 0.301 | ||||||||||
| ≤5 | 3 | 2.56 (1.79, 3.67) | 43.5 | 0.170 | 1.77 (1.34, 2.35) | 0.0 | 0.373 | 1.23 (1.08, 1.40) | 60.4 | 0.080 | |||
| >5 | 2 | 2.22 (1.67, 2.96) | 0.0 | 0.502 | 1.81 (1.42, 2.30) | 0.0 | 0.408 | 1.11 (0.95, 1.29) | 92.1 | <0.001 | |||
| Study quality | 0.355 | 0.729 | 0.782 | ||||||||||
| NOS score, ≤7 | 3 | 2.59 (1.86, 3.61) | 43.2 | 0.172 | 1.85 (1.44, 2.37) | 8.6 | 0.335 | 1.21 (0.99, 1.47) | 87.7 | <0.001 | |||
| NOS score, >7 | 2 | 2.16 (1.60, 2.93) | 0.0 | 0.640 | 1.73 (1.32, 2.26) | 0.0 | 0.549 | 1.17 (1.10, 1.24) | 0.0 | 0.378 | |||
| No. of cases | 0.394 | 0.586 | 0.454 | ||||||||||
| ≤200 | 2 | 5.22 (0.78, 35.09) |
69.3 | 0.071 | 1.95 (1.36, 2.81) | 23.2 | 0.254 | 1.33 (0.91, 1.95) | 77.0 | 0.037 | |||
| >200 | 3 | 2.27 (1.78, 2.88) | 0.0 | 0.773 | 1.74 (1.41, 2.15) | 0.0 | 0.585 | 1.14 (1.00, 1.30) | 90.1 | <0.001 | |||
| DII components | 0.355 | 0.729 | 0.782 | ||||||||||
| <27 | 3 | 2.59 (1.86, 3.61) | 43.2 | 0.172 | 1.85 (1.44, 2.37) | 8.6 | 0.335 | 1.21 (0.99, 1.47) | 87.7 | <0.001 | |||
| ≥27 | 2 | 2.16 (1.60, 2.93) | 0.0 | 0.640 | 1.73 (1.32, 2.26) | 0.0 | 0.549 | 1.17 (1.10, 1.24) | 0.0 | 0.378 | |||
| E-DII | 0.942 | 0.456 | 0.395 | ||||||||||
| No | 1 | 2.38 (1.52, 3.72) | – | – | 1.54 (1.00, 2.38) | – | – | 1.24 (1.10, 1.38) | – | – | |||
| Yes | 4 | 2.34 (1.80, 3.03) | 31.6 | 0.226 | 1.85 (1.51, 2.26) | 0.0 | 0.549 | 1.15 (1.03, 1.29) | 86.4 | <0.001 | |||
| Adjustment | |||||||||||||
| Age/gender | 0.417 | 0.683 | 0.181 | ||||||||||
| Yes | 3 | 2.26 (1.74, 2.94) | 0.0 | 0.763 | 1.82 (1.49, 2.24) | 0.0 | 0.701 | 1.11 (1.00, 1.24) | 87.2 | <0.001 | |||
| No | 2 | 5.08 (0.73, 35.33) |
71.6 | 0.061 | 1.65 (1.08, 2.53) | 44.1 | 0.181 | 1.38 (1.03, 1.84) | 62.0 | 0.105 | |||
| SES | 0.052 | 0.223 | 0.039 | ||||||||||
| Yes | 4 | 2.29 (1.83, 2.87) | 0.0 | 0.902 | 1.77 (1.47, 2.13) | 0.0 | 0.757 | 1.14 (1.03, 1.26) | 86.7 | <0.001 | |||
| No | 1 | 18.46 (2.28, 149.72) |
– | – | 5.43 (0.90, 32.65) |
– | – | 1.69 (1.18, 2.43) | – | – | |||
| BMI | 0.545 | 0.545 | 0.301 | ||||||||||
| Yes | 2 | 2.22 (1.67, 2.96) | 0.0 | 0.502 | 2.22 (1.67, 2.96) | 0.0 | 0.502 | 1.11 (0.95, 1.29) | 92.1 | <0.001 | |||
| No | 3 | 2.56 (1.79, 3.67) | 43.5 | 0.170 | 2.56 (1.79, 3.67) | 43.5 | 0.170 | 1.23 (1.08, 1.40) | 60.4 | 0.080 | |||
| Family history of cancer | 0.700 | 0.485 | <0.001 | ||||||||||
| Yes | 1 | 2.57 (1.54, 4.29) | – | – | 1.96 (1.43, 2.67) | – | – | 1.03 (1.00, 1.06) | – | – | |||
| No | 4 | 2.30 (1.79, 2.95) | 28.6 | 0.240 | 1.71 (1.36, 2.14) | 0.0 | 0.536 | 1.19 (1.13, 1.26) | 40.9 | 0.166 | |||
DII, dietary inflammatory index; OR, odds ratio; CI, confidence interval; NOS, Newcastle–Ottawa Quality Assessment Scale; E-DII, energy adjusted DII; SES, Socio-economic status; BMI, body mass index.
a
p-value for heterogeneity within each subgroup.
b
p-value for heterogeneity between subgroups using Z-test.