Table 3

Associations between screen time weekends and BMD at different sites in 15–18 years old girls and boys, at FF1 (2010/2011) and FF2 (2013/2013)

	Girls (n=388_FF1/312_FF2)				Boys (n=359_FF1/231_FF2)
	Unadjusted		Adjusted*		Unadjusted		Adjusted*
Screen time categories†	β‡	95% CI	β‡	95% CI	β‡	95% CI	β‡	95% CI
FF1
BMD_TH, h
2–4	0.018	−0.016 to 0.051	0.025	−0.008 to 0.059	−0.031	−0.077 to 0.016	−0.061	−0.111 to −0.011
4–6	0.028	−0.005 to 0.061	0.054	0.017 to 0.090	−0.002	−0.045 to 0.041	−0.038	−0.087 to 0.011
≥6	0.011	−0.030 to 0.052	0.042	−0.006 to 0.090	−0.051	−0.096 to −0.006	−0.062	−0.120 to −0.004
BMD_FN, h
2–4	0.033	<0.001 to 0.066	0.046	0.012 to 0.079	−0.035	−0.082 to 0.013	−0.063	−0.113 to −0.014
4–6	0.036	0.003 to 0.069	0.070	0.034 to 0.106	−0.005	−0.049 to 0.039	−0.034	−0.083 to 0.014
≥6	0.010	−0.031 to 0.051	0.058	0.010 to 0.105	−0.061	−0.107 to −0.015	−0.064	−0.121 to −0.007
BMD_TB, h
2–4	0.010	−0.011 to 0.030	0.015	−0.003 to 0.033	−0.030	−0.060 to 0.001	−0.039	−0.068 to −0.010
4–6	0.011	−0.009 to 0.031	0.023	0.003 to 0.042	−0.009	−0.037 to 0.020	−0.028	−0.056 to 0.001
≥6	0.005	−0.021 to 0.030	0.017	−0.009 to 0.043	−0.034	−0.063 to −0.004	−0.030	−0.064 to 0.004
FF2
BMD_TH, h
2–4	0.010	−0.030 to 0.050	0.017	−0.025 to 0.058	−0.052	−0.117 to 0.012	−0.074	−0.141 to −0.007
4–6	−0.002	−0.042 to 0.038	0.024	−0.021 to 0.068	−0.039	−0.099 to 0.021	−0.060	−0.127 to 0.007
≥6	−0.014	−0.066 to 0.038	0.016	−0.048 to 0.079	−0.060	−0.123 to 0.002	−0.063	−0.142 to 0.017
BMD_FN, h
2–4	0.016	−0.024 to 0.057	0.027	−0.015 to 0.068	−0.047	−0.112 to 0.017	−0.061	−0.128 to 0.005
4–6	0.002	−0.039 to 0.042	0.036	−0.009 to 0.081	−0.035	−0.096 to 0.025	−0.041	−0.107 to 0.025
≥6	−0.015	−0.067 to 0.038	0.030	−0.034 to 0.093	−0.052	−0.115 to 0.010	−0.038	−0.116 to 0.041
BMD_TB, h
2–4	0.005	−0.018 to 0.028	0.011	−0.010 to 0.032	−0.032	−0.070 to 0.007	−0.033	−0.069 to 0.004
4–6	−0.006	−0.029 to 0.017	0.013	−0.010 to 0.036	−0.023	−0.059 to 0.013	−0.029	−0.066 to 0.007
≥6	−0.021	−0.051 to 0.009	0.004	−0.029 to 0.036	−0.033	−0.070 to 0.004	−0.017	−0.060 to 0.027

*Adjusted for age, body mass index, height, sexual maturation, physical activity, calcium intake, vitamin D levels, soft drinks and alcohol consumption, smoking habits and screen time weekdays.
†Screen time categories compared to <2 h per day during weekends.
‡β Values displayed as g/cm², statistically significant results at 5% level in bold.
BMD, bone mineral density; BMD_TH, BMD at total hip; BMD_FN, BMD at femoral neck; BMD_TB, BMD at total body; FF1, Fit Futures 1; FF2, Fit Futures 2.