Health Services Research & Development

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2007 HSR&D National Meeting Abstract

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National Meeting 2007

3071 — The Relationship Between Health Literacy and Hypertension. Do Health Systems Predict Differences?

Powers BJ (Durham VA COE) , Oddone EZ (Durham VA COE), Olsen MK (Durham VA COE), Bosworth HB (Durham VA COE)

Objectives:
Low literacy is prevalent and is associated with poor health outcomes. Our goals were to: 1.) Determine the independent relationship of low literacy with systolic blood pressure (SBP) in patients in hypertension and 2.) Identify health system differences that may influence this relationship.

Methods:
Patient information (n=1173) was drawn from combined baseline data from the Veterans Study to Improve the Control of Hypertension (VSTITCH) and the community clinic based Take Control of Your Blood Pressure (TCYB). Literacy was assessed using the Rapid Estimate of Adult Literacy in Medicine (REALM). Using a linear regression model, we determined the association of low literacy with SBP after adjusting for patient and clinic characteristics significantly associated with systolic blood pressure. Finally, we conducted a test of interaction to determine if the health system (VA vs. non-VA) modified the relationship between literacy and SBP.

Results:
Patients with low literacy (REALM score <61) were more likely to be male, non-white, have low educational attainment, report inadequate income, and receive their care in the VA. Patients with low literacy had significantly higher SBP than patients with high literacy with a mean difference of 5.2mmHg (95% CI: 2.8-7.5 mmHg; p<0.001). After adjusting for demographic factors, hypertension knowledge, and medication adherence, the difference in mean SBP between low literacy and high literacy patients was 2.3mmHg (95% CI: -0.24-4.9; p =0.08). We found a strong interaction between health system and literacy on SBP that explained most of the observed difference in SBP between low and high literacy patients. In the VA, the mean SBP difference between low and high literacy patients was 0.4mmHg compared to 9.3mmHg in non-VA patients (p-value for test of interaction <0.0001).

Implications:
This is the first study to show a significant difference in BP between low and high literacy patients. This difference was greatest among non-VA patients who received care in a community clinic practice.

Impacts:
Health system organizational factors may significantly influence the impact of literacy on BP. Some of the previously reported associations of literacy and health outcomes may not apply to patients receiving care in the VA health system.