Table 2.

Univariable negative binomial regression models for the association of baseline demographic and clinical variables with the change in SDI score during follow-up among SLE patients in the SLICC inception cohort (n=1549).

Independent variable	Incidence Rate Ratio (95% CI)	p value
Baseline age (years)	1.015 (1.010 – 1.020)	<0.0001
Male Sex	1.66 (1.33 – 2.07)	<0.0001
Race/ethnicity: Caucasian	Referent
Hispanic	1.37 (1.09 – 1.73)	0.007
Black	1.82 (1.46 – 2.26)	<0.001
Asian	0.72 (0.56 – 0.92)	0.008
Other	1.55 (1.04– 2.31)	0.030
Geographic location: USA	Referent
Canada	0.53 (0.42 – 0.66)	<0.001
Mexico	0.77 (0.59 – 1.02)	0.064
Europe	0.52 (0.42 – 0.64)	<0.001
Asia	0.38 (0.28 – 0.52)	<0.001
Post-secondary educationa: No	Referent
Yes	0.80 (0.68 – 0.95)	0.009
Cigarette smoking: No	Referent
Yes	1.09 (0.87 – 1.36)	0.449
Corticosteroid use at baseline: No	Referent
Yes	1.49 (1.24 – 1.78)	<0.0001
Immunosuppressive use at baseline: No	Referent
Yes	1.44 (1.22 – 1.70)	<0.0001
Antimalarial use at baseline: No	Referent
Yes	0.79 (0.67 – 0.94)	0.007
SLEDAI-2Kb at baseline (per 1.0)	1.05 (1.03 – 1.07)	<0.0001
SLE disease duration at baseline (years)	1.00 (0.99 – 1.01)	0.528
Lupus-anticoagulant at baseline c: No	Referent
Yes	1.19 (0.94 – 1.50)	0.152
Anti-cardiolipin at baseline c: No	Referent
Yes	1.23 (0.92 – 1.65)	0.164
Anti-beta-2-glycoprotein I at baseline c: No	Referent
Yes	1.06 (0.76 – 1.50)	0.727

^aA “missing” indicator was included for the 1.4% of patients for whom this data was lacking.

^bSLEDAI-2K = SLE disease activity index 2000

^cAnalysis included 911 patients with complete antiphospholipid antibody data