Literacy and blood pressure – do healthcare systems influence this relationship? A cross-sectional study

Table 2 Multiple linear regression model – outcome: systolic blood pressure

Parameter	β Coefficient (95% CI)	Standard Error	t Value	P-value
Intercept	*130.0 (120.0, 140.0)*	*5.1*	*25.5*	*<0.001*
Main Effects
Age, 10 years (continuous)*	1.9 (0.9, 2.9)	0.5	3.8	<0.001
Race (white vs. non-white (ref))	-5.0 (-7.5, -2.6)	1.3	-4.0	<0.001
Currently Married (yes vs. no (ref))	-0.2 (-2.5, 2.2)	1.2	-0.1	0.89
Education (college graduate ref)
0–9^th grade	0.1 (-4.6, 4.8)	2.4	0.05	0.96
10^th-12^th grade	1.0 (-2.1, 4.0)	1.6	0.6	0.54
Some college/vocational tech	1.9 (-1.1, 4.9)	1.5	1.3	0.20
Diabetes (yes vs. no (ref))	-0.7 (-3.1, 1.6)	1.2	-0.6	0.53
Inadequate Income (yes vs. no (ref))	1.3 (-1.6, 4.3)	1.5	0.9	0.37
Medication Adherence (nonadherent vs. adherent (ref))	3.7 (1.3, 6.2)	1.2	3.0	0.003
Current Smoker (yes vs. no (ref))	-2.4 (-5.3, 0.6)	1.5	-1.6	0.11
Current Exerciser (yes vs. no (ref))	1.3 (-1.2, 3.8)	1.3	1.1	0.29
Participatory Decision Making Score (continuous)	-0.1 (-0.3, 0.1)	0.1	-1.0	0.31
Interaction
Literacy by Healthcare System †,	7.4 (2.5, 12.3)	2.5	3.0	0.003
Literacy main effect‡ (REALM < 9^th grade vs. ≥ 9^th grade (ref))	-1.2 (-4.8, 2.3)	1.8	-	-
Healthcare System main effect‡ (UHS vs. VAHS (ref))	-5.4 (-8.2, -2.6)	1.4	-	-

Total number of patients included in model = 1082.
Positive coefficients represent higher systolic blood pressure; negative coefficients represent lower systolic blood pressure.
* Each ten-year increase in age is associated with a 1.86 mmHg increase in SBP.
† The reference groups for the interaction term are the same as for the main effects.
‡ Main effect of literacy and healthcare system should be interpreted in conjunction with interaction term.

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