Table 3.

Association between Average caffeine intake (g/day) and lumbar bone mineral density (g/cm²), stratified by age and gender.

Quintiles of average caffeine intake (g/day)	Lumbar bone mineral density (g/cm2), β (95% Cl)
	Male	Female
20–29 years old	0.025 (-0.029, 0.078)	0.056 (-0.012, 0.125)
Lowest quartiles	reference	reference
2nd	0.004 (-0.017, 0.025)	-0.007 (-0.026, 0.012)
3rd	-0.003 (-0.024, 0.019)	0.006 (-0.013, 0.026)
4th	-0.019 (-0.042, 0.003)	0.014 (-0.008, 0.036)
P for trend	0.096	0.158
30–39 years old	0.023 (-0.024, 0.071)	0.080 (0.019, 0.142)*
Lowest quartiles	reference	reference
2nd	-0.006 (-0.033, 0.020)	0.009 (-0.014, 0.033)
3rd	-0.012 (-0.037, 0.012)	0.012 (-0.013, 0.036)
4th	0.003 (-0.020, 0.026)	0.025 (0.000, 0.050)*
P for trend	0.748	0.049
40–49 years old	-0.070 (-0.113, -0.026)**	0.007 (-0.041, 0.054)
Lowest quartiles	reference	reference
2nd	0.001 (-0.032, 0.033)	0.013 (-0.015, 0.040)
3rd	0.016 (-0.018, 0.049)	0.020 (-0.007, 0.047)
4th	-0.027 (-0.058, 0.004)	0.011 (-0.016, 0.037)
P for trend	0.026	0.553

All variables were adjusted.

*P<0.05, **P<0.01.