Table 2.
Parameter estimates (95% CIs) for baseline and 10-yr change in lumbar spine, femoral neck, and total hip BMD with baseline sedentary behavior (in quartiles of sitting time, h/d; reference = first quartile, ie, lowest sitting time).
| Outcome | Variables in models | Women | Men | ||||
|---|---|---|---|---|---|---|---|
| Second quartile | Third quartile | Fourth quartile | Second quartile | Third quartile | Fourth quartile | ||
| 5.0–6.0 h/d | 6.5–8.0 h/d | >8.5 h/d | 5.5–7.0 h/d | 7.–9.0 h/d | >9.5 h/d | ||
| Cross-sectional analyses with baseline BMD (g/cm 2 ) | |||||||
| Lumbar spine BMD | 1: Unadjusted | −0.018 (−0.030 to −0.005) | −0.004 (−0.017 to 0.009) | 0.024 (0.011 to 0.038) | 0.010 (−0.008 to 0.028) | 0.001 (−0.018 to 0.020) | 0.007 (−0.012 to 0.025) |
| 2: + age + covariatesa | −0.001 (−0.012 to 0.011) | 0.007 (−0.005 to 0.019) | 0.008 (−0.004 to 0.020) | 0.002 (−0.017 to 0.020) | 0.005 (−0.014 to 0.025) | 0.009 (−0.009 to 0.031) | |
| 3: + BMI | −0.007 (−0.018 to 0.004) | −0.003 (−0.015 to 0.008) | −0.005 (−0.017 to 0.007) | −0.002 (−0.020 to 0.016) | −0.001 (−0.020 to 0.018) | 0.003 (−0.016 to 0.023) | |
| Femoral neck BMD | 1: Unadjusted | −0.017 (−0.026 to −0.008) | −0.015 (−0.024 to −0.005) | 0.014 (0.004 to 0.024) | 0.002 (−0.012 to 0.015) | −0.002 (−0.016 to 0.012) | 0.026 (0.012–0.040) |
| 2: + age + covariatesb | 0.000 (−0.008 to 0.008) | −0.001 (−0.009 to 0.007) | 0.000 (−0.008 to 0.009) | 0.001 (−0.012 to 0.014) | −0.010 (−0.023 to 0.003) | 0.000 (−0.013 to 0.014) | |
| 3: + BMI | −0.005 (−0.012 to 0.002) | −0.009 (−0.016 to −0.002) | −0.010 (−0.018 to −0.002) | −0.002 (−0.014 to 0.010) | −0.015 (−0.027 to −0.002) | −0.007 (−0.020 to 0.006) | |
| Total hip BMD | 1: Unadjusted | −0.016 (−0.027 to −0.006) | −0.013 (−0.024 to −0.003) | 0.019 (0.008–0.030) | 0.006 (−0.010 to 0.022) | 0.002 (−0.015 to 0.019) | 0.023 (0.007–0.040) |
| 2: + age + covariatesc | 0.003 (−0.006 to 0.012) | 0.003 (−0.006 to 0.013) | 0.008 (−0.002 to 0.018) | 0.006 (−0.009 to 0.021) | −0.003 (−0.019 to 0.013) | 0.006 (−0.011 to 0.022) | |
| 3: + BMI | −0.005 (−0.013 to 0.003) | −0.009 (−0.017 to 0.000) | −0.007 (−0.016 to 0.002) | 0.001 (−0.013 to 0.015) | −0.010 (−0.025 to 0.005) | −0.005 (−0.020 to 0.010) | |
| Longitudinal analyses with 10-yr change in BMD (g/cm 2 ) | |||||||
| Lumbar spine BMD | 1: Unadjusted | 0.016 (0.007 to 0.025) | 0.017 (0.008 to 0.025) | −0.005 (−0.014 to 0.004) | −0.001 (−0.013 to 0.010) | −0.008 (−0.020 to 0.004) | −0.013 (−0.025 to −0.002) |
| 2: + age + covariatesd | 0.006 (−0.002 to 0.013) | 0.006 (−0.002 to 0.013) | 0.002 (−0.007 to 0.011) | −0.004 (−0.015 to 0.007) | −0.008 (−0.019 to 0.004) | −0.006 (−0.018 to 0.005) | |
| 3: + BMI | 0.005 (−0.003 to 0.013) | 0.005 (−0.003 to 0.013) | 0.001 (−0.007 to 0.009) | −0.005 (−0.016 to 0.006) | −0.009 (−0.020 to 0.003) | −0.007 (−0.019 to 0.004) | |
| Femoral neck BMD | 1: Unadjusted | 0.003 (−0.002 to 0.009) | 0.003 (−0.002 to 0.009) | 0.002 (−0.004 to 0.007) | −0.000 (−0.009 to 0.008) | 0.003 (−0.006 to 0.011) | −0.005 (−0.013 to 0.003) |
| 2: + age + covariatese | 0.001 (−0.005 to 0.006) | 0.001 (−0.004 to 0.007) | 0.004 (−0.002 to 0.010) | 0.001 (−0.008 to 0.009) | 0.003 (−0.005 to 0.012) | −0.005 (−0.013 to 0.004) | |
| 3: + BMI | 0.002 (−0.004 to 0.007) | 0.002 (−0.003 to 0.008) | 0.005 (−0.001 to 0.011) | 0.001 (−0.007 to 0.009) | 0.004 (−0.005 to 0.013) | −0.004 (−0.012 to 0.005) | |
| Total hip BMD | 1: Unadjusted | 0.002 (−0.004 to 0.008) | 0.005 (−0.001 to 0.011) | 0.005 (−0.001 to 0.011) | −0.008 (−0.018 to 0.001) | 0.000 (−0.10 to 0.010) | −0.005 (−0.014 to 0.005) |
| 2: + age + covariatesf | 0.002 (−0.004 to 0.008) | 0.004 (−0.002 to 0.010) | 0.004 (−0.002 to 0.010) | −0.005 (−0.014 to 0.004) | −0.001 (−0.010 to 0.008) | −0.006 (−0.015 to 0.003) | |
| 3: + BMI | 0.003 (−0.003 to 0.009) | 0.005 (−0.001 to 0.011) | 0.006 (−0.000 to 0.012) | −0.004 (−0.013 to 0.004) | 0.000 (−0.009 to 0.009) | −0.005 (−0.014 to 0.004) | |
aCovariates for L1–L4 BMD: For women: height, education, center, smoking, alcohol, physical activity, walking, weight cycling, caffeine intake, vitamin D intake, osteoporosis diagnosis, prior clinical fragility fracture, antiresorptive use, corticosteroid use, combined hormonal contraceptives (CHC); for men: height, White, center, smoking, alcohol, physical activity, walking, weight cycling, calcium intake, osteoporosis diagnosis, prior clinical fragility fracture, parental fracture, corticosteroid use, comorbidities.
bCovariates for femoral neck BMD: For women: height, education, center, smoking, alcohol, physical activity, walking, weight cycling, caffeine intake, vitamin D intake, osteoporosis diagnosis, prior clinical fragility fracture, antiresorptive use, corticosteroid use, CHC, comorbidities; For men: education, height, center, smoking, alcohol, physical activity, walking, weight cycling, calcium intake, osteoporosis diagnosis, prior clinical fragility fracture, corticosteroid use, comorbidities, hours of sleep.
cCovariates for total hip BMD: For women: height, education, center, alcohol, physical activity, walking, weight cycling, vitamin D intake, osteoporosis diagnosis, prior clinical fragility fracture, antiresorptive use, corticosteroids, CHC, comorbidities; For men: education, height, center, smoking, alcohol, physical activity, walking, weight cycling, calcium intake, osteoporosis diagnosis, prior clinical fragility fracture, corticosteroid use, hours of sleep.
dCovariates for L1–L4 BMD: For women: height, education, center, alcohol, physical activity, walking, caffeine intake, vitamin D intake, calcium intake, osteoporosis diagnosis, prior clinical fragility fracture, comorbidities, CHC; For men: height, center, smoking, physical activity, walking, vitamin D intake, antiresorptive use.
eCovariates for femoral neck BMD: For women: height, education, center, physical activity, walking, weight cycling, calcium intake, osteoporosis diagnosis, prior clinical fragility fracture, antiresorptive use, corticosteroid use, comorbidities, CHC; For men: height, center, physical activity, walking, weight cycling.
fCovariates for total hip BMD: For women: height, White, physical activity, walking, weight cycling, antiresorptive use, comorbidities; For men: height, White, center, physical activity, walking, weight cycling, antiresorptive use, comorbidities.
Univariate linear regression models were fit for each baseline covariable with each baseline BMD site. Variables reaching statistical significance (P < .05) were included in the respective model.