Association of health literacy with elevated blood pressure: a cohort study of hospitalized patients.

Background: The clinical consequences of low health literacy are not fully understood.
Objectives: We evaluated the relationship between low health literacy and elevated blood pressure (BP) at hospital presentation.
Research Design and Subjects: We conducted a cross-sectional evaluation of adult patients hospitalized at a university hospital between November 1, 2010 and April 30, 2012.
Measures: Health literacy was assessed using the Brief Health Literacy Screen (BHLS). Low health literacy was defined as a BHLS score ≤9. BP was assessed using clinical measurements. The outcome was elevated BP (≥140/90 mm Hg; ≥130/80 mm Hg with diabetes or renal disease) or extremely elevated BP (>160/100 mm Hg) at hospital presentation. Multivariate logistic regression adjusted for age, sex, race, insurance, comorbidities, and antihypertensive medications; preplanned restricted analysis among patients with diagnosed hypertension was performed.
Results: Of 46,263 hospitalizations, 23% had low health literacy, which occurred more often among patients who were older (61 vs. 54 y), less educated (28.4% vs. 11.2% had not completed high school), and more often admitted through the emergency department (54.3% vs. 48.1%) than those with BHLS>9. Elevated BP was more frequent among those with low health literacy [40.0% vs. 35.5%; adjusted odds ratio (aOR) 1.06; 95% confidence interval (CI), 1.01-1.12]. Low health literacy was associated with extremely elevated BP (aOR 1.08; 95% CI, 1.01-1.16) and elevated BP among those without diagnosed hypertension (aOR 1.09; 95% CI, 1.02-1.16).
Conclusions: More than ⅓ of patients had elevated BP at hospital presentation. Low health literacy was independently associated with elevated BP, particularly among patients without diagnosed hypertension.