Table 1.
Subgroup analyses of BMI and kidney stones
| BMI, per 5 kg/m2 | |||||
|---|---|---|---|---|---|
| n | RR (95% CI) | I2 (%) | P ah | P bh | |
| All studies | 8 | 1.21 (1.12–1.30) | 76.4 | < 0.0001 | |
| Sex | |||||
| Men | 3 | 1.24 (1.13–1.36) | 0 | 0.64 | 0.72/0.96c |
| Women | 4 | 1.22 (1.05–1.42) | 88.5 | < 0.0001 | |
| Men and women | 1 | 1.09 (0.86–1.37) | |||
| Assessment of weight/height | |||||
| Measured | 5 | 1.11 (1.07–1.16) | 0 | 0.62 | 0.003 |
| Self-reported | 3 | 1.32 (1.23–1.41) | 32.4 | 0.23 | |
| Duration of follow-up | |||||
| < 10 years follow-up | 3 | 1.12 (1.07–1.17) | 0 | 0.91 | 0.14 |
| ≥ 10 years follow-up | 5 | 1.27 (1.14–1.41) | 78.4 | 0.001 | |
| Geographic location | |||||
| Europe | 0 | 0.20 | |||
| America | 4 | 1.26 (1.12–1.41) | 86.9 | < 0.0001 | |
| Asia | 4 | 1.12 (1.05–1.18) | 0 | 0.45 | |
| Number of cases | |||||
| Cases < 500 | 0 | 0.99 | |||
| Cases 500 to < 1000 | 2 | 1.22 (0.91–1.66) | 46.6 | 0.17 | |
| Cases ≥ 1000 | 4 | 1.26 (1.12–1.41) | 86.9 | < 0.0001 | |
| Study quality | |||||
| 0–3 | 0 | 0.36 | |||
| 4–6 | 1 | 1.49 (1.01–2.21) | |||
| 7–9 | 7 | 1.20 (1.11–1.29) | 78.7 | < 0.0001 | |
| Adjustment for confounders | |||||
| Age | |||||
| Yes | 8 | 1.21 (1.12–1.30) | 76.4 | < 0.0001 | NC |
| No | 0 | ||||
| Alcohol | |||||
| Yes | 4 | 1.29 (1.20–1.40) | 45.0 | 0.14 | 0.007 |
| No | 4 | 1.12 (1.07–1.16) | 0 | 0.46 | |
| Smoking | |||||
| Yes | 4 | 1.12 (1.05–1.18) | 0 | 0.45 | 0.20 |
| No | 4 | 1.26 (1.12–1.41) | 86.9 | < 0.0001 | |
| Diabetes | |||||
| Yes | 4 | 1.11 (1.07–1.15) | 0 | 0.93 | 0.002 |
| No | 4 | 1.32 (1.25–1.41) | 10.0 | 0.34 | |
| Thiazide use | |||||
| Yes | 3 | 1.32 (1.23–1.41) | 32.4 | 0.23 | 0.003 |
| No | 5 | 1.11 (1.07–1.16) | 32.4 | 0.23 | |
| Fluids | |||||
| Yes | 3 | 1.32 (1.23–1.41) | 32.4 | 0.23 | 0.003 |
| No | 5 | 1.11 (1.07–1.16) | 0 | 0.62 | |
| Sodium | |||||
| Yes | 4 | 1.29 (1.20–1.40) | 45.0 | 0.14 | 0.007 |
| No | 4 | 1.12 (1.07–1.16) | 0 | 0.46 | |
| Potassium | |||||
| Yes | 6 | 1.22 (1.11–1.33) | 76.2 | 0.001 | 0.69 |
| No | 2 | 1.21 (0.93–1.56) | 53.0 | 0.15 | |
| Animal protein, protein | |||||
| Yes | 5 | 1.23 (1.12–1.35) | 80.1 | < 0.0001 | 0.43 |
| No | 3 | 1.12 (1.04–1.21) | 8.5 | 0.34 | |
| Dietary calcium | |||||
| Yes | 7 | 1.20 (1.11–1.29) | 78.7 | < 0.0001 | 0.36 |
| No | 1 | 1.49 (1.01–2.21) | |||
| Calcium supplements | |||||
| Yes | 3 | 1.12 (1.04–1.21) | 8.5 | 0.34 | 0.003 |
| No | 5 | 1.30 (1.21–1.40) | 32.2 | 0.21 | |
| Physical activity | |||||
| Yes | 5 | 1.11 (1.07–1.16) | 0 | 0.62 | 0.003 |
| No | 3 | 1.32 (1.23–1.41) | 32.4 | 0.23 | |
n denotes the number of studies
aP for heterogeneity within each subgroup
bP for heterogeneity between subgroups
cP for heterogeneity between men and women (excluding men/women combined)