Table 4.

Association of HBA gene copy number with incident ESKD– analysis adjusted for all listed covariates

Characteristic	Incident ESKDa (n=9905) Cox Proportional Hazards
	HR	95% CI	P Valueb
HBA copy number, per gene copy	1.32	(1.09 to 1.61)	0.005
Sickle cell trait	1.85	(1.34 to 2.56)	0.0002
APOL1 high-risk	1.72	(1.31 to 2.27)	0.0001
Hemoglobin, per 1 g/dl	0.61	(0.55 to 0.67)	<0.0001
Age, per year	1.00	(0.99 to 1.02)	0.66
Female sex	0.41	(0.32 to 0.54)	<0.0001
Body mass indexc	1.05	(0.93 to 1.18)	0.46
Hypertension	4.01	(2.49 to 6.44)	<0.0001
Diabetes mellitus	3.42	(2.70 to 4.32)	<0.0001
Smoking status
Never (ref)	—	—
Past	1.19	(0.93 to 1.18)	0.16
Present	1.97	(1.43 to 2.72)	<0.0001
Medically insured	0.91	(0.62 to 1.36)	0.65
Region
Non-belt (ref)	—	—
Belt	0.85	(0.66 to 1.09)	0.20
Buckle	0.97	(0.72 to 1.30)	0.85
Education level
<HS grad (ref)	—	—
HS grad	1.24	(0.90 to 1.70)	0.19
Some college	1.04	(0.73 to 1.46)	0.84
≥College grad	1.30	(0.89 to 1.89)	0.17
Income
<$20K (ref)	—	—
$20K–34K	1.03	(0.77 to 1.38)	0.83
$35K–74K	0.70	(0.49 to 1.00)	0.05
≥$75K	0.42	(0.22 to 0.80)	0.008

All variables in the table were included in the multivariable model. Multiple imputations were performed for missing data. The number of participants available for this analysis was n=9905. APOL1, apolipoprotein-L1; ref, reference category; –, reference category; HS, high school; grad, graduate; K, thousand.

^aIncident ESKD was identified by linkage to the USRDS through December 31, 2018.

^bAnalysis was performed using Cox proportional hazards multivariable regression employing a linear effect of HBA allele count on the log of the HR.

^cBody mass index was scaled by SD.