Table 6.
IV estimates of the effect of fat mass on bone mineral density (BMD) using all available dataa
| SNPs used as instrumental variable | N | First stage regression coefficient (95% CI) | First stage R2 | First stage F-statistic | Ratio of geometric mean BMDb (95% CI) | SE of estimate (log scale) | Hausman test p-value | Sargan test p-value |
|---|---|---|---|---|---|---|---|---|
| OLS | 5509 | NA | NA | NA | 1.22 (1.18, 1.25), p < 0.001 | 0.014 | NA | NA |
| IV: SNP(s) used as IV | ||||||||
| FTO | 5091 | 0.12 (0.08, 0.15) | 0.0088 | 45.35 | 1.41 (1.05, 1.89), p = 0.023 | 0.15 | 0.320 | NA |
| MC4R | 5412 | 0.09 (0.05, 0.13) | 0.0037 | 19.95 | 2.42 (1.42, 4.12), p = 0.001 | 0.27 | 0.002 | NA |
| TMEM18 | 5323 | −0.06 (−0.11, −0.02) | 0.0013 | 6.99 | 2.17 (0.92, 5.12), p = 0.077 | 0.44 | 0.130 | NA |
| GNPDA2 | 5303 | 0.05 (0.01, 0.08) | 0.0013 | 6.90 | 0.92 (0.42, 2.01), p = 0.84 | 0.40 | 0.463 | NA |
| FTO, MC4R | 5007 | NA | 0.0125 | 31.61 | 1.60 (1.24, 2.07), p < 0.001 | 0.13 | 0.029 | 0.221 |
| FTO, MC4R, TMEM18 | 4881 | NA | 0.0138 | 22.75 | 1.69 (1.32, 2.17), p < 0.001 | 0.13 | 0.006 | 0.227 |
a
Analyses adjusted for height and height squared.
b
For a 1 unit increase in z-score of age and gender standardised fat mass.