Non-linear relationships of cerebrospinal fluid biomarker levels with cognitive function: an observational study

Table 2 Parameters of the CSF biomarkers and their relations to cognitive impairment, above and below their change-points

CSF Biomarker	Aβ_1-40		Aβ_1-42		Tau		Phospho-Tau
Cf change-point	Above	Below	Above	Below	Above	Below	Above	Below
Median	5,052	3,937**	682	350**	259	568**	50	80**
Variance	3,857,482	1,854,983**	36,846	71,482**	176,946	73,418**	1,700	1,000**
Spearman's ρ	0.21*	-0.23*	-0.24*	-0.12	0.34**	0.28**	0.32**	0.16
Robust slope	93**	-15**	-0.048**	-0.002	0.049*	0.004**	0.041**	0.004**

The values in the first row are the raw biomarker levels (pg/mL); the second row shows the variance of the median-standardised levels; the third row shows Spearman's ρs for the rank correlations of biomarker levels with CAMCOG scores; the fourth row shows the slopes from the robust regressions of median-standardised biomarker levels. For each biomarker, the "Above" and "Below" columns shows values for CAMCOG scores above and below the change-point, respectively. Note that the correlations and slopes take cognitive impairment as the x-axis, which is the reverse of CAMCOG scores. Key:- ⁽*⁾: 0.10 >P > 0.05; *: P < 0.01; **: P < 0.01. For medians and variances, probabilities refer to the comparison of values above and below the change-point; for Spearman's ρ and slopes they refer to comparison of values with zero.

ISSN: 1758-9193