Table 2.
Physical activity and genetic risk score associations with bone Z-scores
| Males (N=428) | Females (N=476) | Males & Females (N=795) | ||||||
|---|---|---|---|---|---|---|---|---|
| Site | Model | Exposurea | Estimate (95% CI) | P-value | Estimate (95% CI) | P-value | Estimate (95% CI) | P-value |
| SpineaBMD | 1 | Genetic risk score | −0.02 (−0.04, −0.003) | 0.024 | −0.05 (−0.07, −0.03) | 4.6×10−8 | −0.04 (−0.05, −0.02) | 3.4×10−7 |
| 1 | Total Physical Activity | 0.02 (0.01, 0.04) | 0.006 | 0.01 (−0.003, 0.03) | 0.104 | 0.02 (0.01, 0.03) | 0.002 | |
| 2 | High Impact Physical Activity | 0.06 (0.03, 0.08) | 8.0×10−6 | 0.04 (0.01, 0.06) | 0.006 | 0.04 (0.02, 0.06) | 6.6×10−5 | |
| 2 | Low Impact Physical Activity | −0.01 (−0.03, 0.01) | 0.374 | −0.00 (−0.03, 0.02) | 0.698 | 0.00 (−0.02, 0.02) | 0.913 | |
| Total HipaBMD | 1 | Genetic risk score | −0.03 (−0.05, −0.01) | 0.007 | −0.06 (−0.08, −0.04) | 2.7×10−9 | −0.04(−0.06, −0.03) | 1.0×10−7 |
| 1 | Total Physical Activity | 0.02 (0.01, 0.04) | 0.002 | 0.01 (−0.002, 0.02) | 0.086 | 0.02 (0.01, 0.03) | 2.4×10−4 | |
| 2 | High Impact Physical Activity | 0.06 (0.04, 0.09) | 8.0×10−7 | 0.04 (0.02, 0.06) | 7.0×10−5 | 0.05 (0.03, 0.06) | 5.4×10−8 | |
| 2 | Low Impact Physical Activity | −0.01 (−0.03, 0.01) | 0.313 | −0.01 (−0.03, 0.005) | 0.148 | −0.00 (−0.02, 0.01) | 0.599 | |
| Femoral NeckaBMD | 1 | Genetic risk score | −0.03 (−0.05, −0.02) | 5.6×10−4 | −0.06 (−0.08, −0.04) | 7.4×10−9 | −0.04 (−0.06, −0.03) | 5.7×10−9 |
| 1 | Total Physical Activity | 0.03 (0.01, 0.04) | 3.3×10−4 | 0.01 (−0.01, 0.03) | 0.227 | 0.02 (0.01, 0.04) | 1.6×10−4 | |
| 2 | High Impact Physical Activity | 0.08 (0.05, 0.10) | 5.1×10−8 | 0.05 (0.03, 0.08) | 2.9×10−5 | 0.06 (0.04, 0.08) | 2.6×10−9 | |
| 2 | Low Impact Physical Activity | −0.01 (−0.03, 0.01) | 0.466 | −0.02 (−0.05, 0.003) | 0.083 | −0.01 (−0.03, 0.01) | 0.330 | |
| TBLH-BMC | 1 | Genetic risk score | −0.01 (−0.03, 0.002) | 0.094 | −0.04 (−0.05, −0.03) | 3.1×10−9 | −0.03 (−0.04, −0.02) | 1.3×10−6 |
| 1 | Total Physical Activity | 0.02 (0.01, 0.03) | 0.001 | 0.01 (−0.005, 0.02) | 0.192 | 0.02 (0.01, 0.03) | 3.3×10−4 | |
| 2 | High Impact Physical Activity | 0.06 (0.04, 0.08) | 5.5×10−8 | 0.04 (0.02, 0.06) | 6.8×10−6 | 0.05 (0.03, 0.06) | 4.0×10−10 | |
| 2 | Low Impact Physical Activity | −0.01 (−0.03, 0.002) | 0.202 | −0.02 (−0.04, 0.004) | 0.107 | −0.01 (−0.02, 0.01) | 0.219 | |
The estimates for the physical activity variables represent the change in bone Z-scores per additional hour per day spent physically active. The estimates for the genetic risk score represent the change in bone Z-score per additional 1% increase in the genetic risk score.
Genetic risk score, percentage of the number of lowering bone mineral density alleles carried at 63 loci identified in an adult genome wide association study(20).
High Impact Physical Activity, hours per day spent in weight bearing physical activity with a ground reaction force >2× body weight.
Low Impact Physical Activity, hours per day spent in non-weight bearing physical activity or weight bearing physical activity with a ground reaction force 1–2× body weight. All analyses involved participants in the longitudinal discovery cohort using linear mixed models; adjusted for age, puberty stage, body mass index Z-score, and dietary calcium intake (gender was included as a covariate in the male and females combined analyses with older sibling was removed). In model 1, total physical activity and genetic risk score were included with the covariates. In model 2, low and high impact physical activity, as well as genetic risk score, were included with the covariates. Abbreviations: TBLH-BMC, total body less head bone mineral content.