Health Literacy and 1-Year Mortality: Mechanisms of Association in Adults Hospitalized for Cardiovascular Disease.

OBJECTIVE: To test theorized patient-level mediators in the causal pathway between health literacy (HL) and 1-year mortality in adults with cardiovascular disease (CVD). PATIENTS AND METHODS: A total of 3000 adults treated at Vanderbilt University Hospital from October 11, 2011, through December 18, 2015, for acute coronary syndrome or acute decompensated heart failure (ADHF) participated in the Vanderbilt Inpatient Cohort Study. Participants completed a bedside-administered survey and consented to health record review and longitudinal follow-up. Multivariable mediation models examined the direct and indirect effects of HL (a latent variable with 4 indicators) with 1-year mortality after discharge (dichotomous). Hypothesized mediators included social support, health competence, health behavior, comorbidity index, type of CVD diagnosis, and previous-year hospitalizations.
RESULTS: Of the 2977 patients discharged from the hospital (60% male; mean age, 61 years; 83% non-Hispanic white, 37% admitted for ADHF), 17% to 23% had inadequate HL depending on the measure, and 10% (n=304) died within 1 year. The total effect of lower HL on 1-year mortality (adjusted odds ratio [AOR]=1.31; 95% CI, 1.01-1.69) was decomposed into an indirect effect (AOR=1.50; 95% CI, 1.35-1.67) via the mediators and a nonsignificant direct effect (AOR=0.87; 95% CI, 0.66-1.14). Each SD decrease in HL was associated with an absolute 3.2 percentage point increase in the probability of 1-year mortality via mediators admitted for ADHF, comorbidities, health behavior, health competence, and previous-year hospitalizations (listed by contribution to indirect effect).
CONCLUSION: Patient-level factors link low HL and mortality. Health competence and health behavior are modifiable mediators that could be targeted by interventions post hospitalization for CVD.