Table 2.

Results of comparison between linear models and spline models.

	LRT	AIC linear model	AIC spline model
Sample: 2005
Ca levels in men	0.002	−1122	−1131
Ca levels in women	<0.001	−902	−920
P levels in men	<0.001	1559	1356
P levels in women	<0.001	1017	788
Sample: 2010
Ca levels in men	0.175	−443	−443
Ca levels in women	<0.001	−895	−926
P levels in men	<0.001	2120	1940
P levels in women	<0.001	1037	857
Sample: 2014
Ca levels in men	0.012	−1304	−1309
Ca levels in women	<0.001	−1056	−1082
P levels in men	<0.001	2508	2165
P levels in women	<0.001	1633	1217

Italic font: note the negative values: the lower, the better fit.

AIC, Akaike information criteria; LRT, likelihood ratio test.