Table 1.

Classical and quantile regression analyses of HDL-cholesterol and apolipoprotein A1

	Traditional regression analysis		Quantile regression analysis
		Classical regression slope, all observations	Increase in slope per 1% increase in the percentile of the dependent variable’s distribution				Difference in slope between the 90th and 10th percentiles
	Correlation		Linear effect		Nonlinear effects
		Slope±SE	Slope±SE	Linear P	Quadratic P	Cubic P	Difference ±SE	P
Offspring-parent
HDL-cholesterol*	0.27	0.288±0.013¶	0.0013±0.0003	4.2x10−5	0.003	0.68	0.119±0.034	0.0005
Offspring midparental-
HDL-cholesterol*	0.35	0.522±0.022¶	0.0021±0.0006	0.0006	0.09	0.05	0.199±0.054	0.0002
Sibling
HDL-cholesterol†	0.29	0.285±0.016¶	0.0013±0.0004	0.002	0.77	0.62	0.101±0.030	0.0006
Apo A1§	0.27	0.273±0.026¶	0.0018±0.0006	0.006	0.34	0.47	0.166±0.062	0.007
HDL2-cholesterol‡	0.24	0.241±0.027¶	0.0025±0.0008	0.003	0.19	0.65	0.196±0.120	0.10
HDL3-cholesterol‡	0.28	0.279±0.027¶	0.0017±0.0007	0.02	0.66	0.67	0.131±0.061	0.03

^*2800 parent-child pairs in 1372 families with one parent, 7850 parent-child pairs in 1745 families with both parents.

^†5941 siblings in 2130 families with two or more children per family

^§2179 siblings in 819 families

^‡2084 siblings in 789 families

^¶P<10⁻¹⁵