Research in Gerontological Nursing

State of the Science Supplemental Data

Health Literacy and Mortality in Patients With Heart Failure: A Systematic Review and Meta-Analysis

Xibei B. Liu, MD; Yousef Ayatollahi, MD; Takashi Yamashita, PhD; Mohamed Jaradat, MD; Jay J. Shen, PhD; Sun Jung Kim, PhD; Yong-Jae Lee, MD; Jinwook Hwang, MD; Hyeyoung Yeom, MD; Soumya Upadhyay, PhD; Caroline Liu; Haneul Choi; Ji Won Yoo, MD, MS

Abstract

Heart failure (HF) remains the most common diagnosis of hospital admission among U.S. adults. Although diagnosis and treatment have improved, mortality rates have not changed, and mortality risk remains high after hospitalization. The current researchers examined how limited health literacy is associated with mortality risk in adults with recent hospitalization due to decompensated HF. Researchers conducted a systematic literature search, selecting three cohort and three intervention studies. The fixed-effect model was used. From the three cohort studies, 2,858 study participants were analyzed. Among participants, limited health literacy was associated with higher all-cause mortality (pooled odds ratio = 2.95; 95% confidence interval [2.34, 3.72]; p < 0.01; I2 = 47.38%). However, none of the intervention studies showed an association between limited health literacy and cardiac (or all-cause) mortality. Future research should focus on the efficiency and safety of telehealth-based medicine in patients with HF, particularly those with limited health literacy.

[Res Gerontol Nurs. 2019; 12(2):91–108.]

Abstract

Heart failure (HF) remains the most common diagnosis of hospital admission among U.S. adults. Although diagnosis and treatment have improved, mortality rates have not changed, and mortality risk remains high after hospitalization. The current researchers examined how limited health literacy is associated with mortality risk in adults with recent hospitalization due to decompensated HF. Researchers conducted a systematic literature search, selecting three cohort and three intervention studies. The fixed-effect model was used. From the three cohort studies, 2,858 study participants were analyzed. Among participants, limited health literacy was associated with higher all-cause mortality (pooled odds ratio = 2.95; 95% confidence interval [2.34, 3.72]; p < 0.01; I2 = 47.38%). However, none of the intervention studies showed an association between limited health literacy and cardiac (or all-cause) mortality. Future research should focus on the efficiency and safety of telehealth-based medicine in patients with HF, particularly those with limited health literacy.

[Res Gerontol Nurs. 2019; 12(2):91–108.]

Heart failure (HF) is a disease causing shortness of breath, swelling, and/or fatigue by changing structure and function of the heart. It is commonly caused by conditions such as cardiomyopathy or hypertension. Lifestyle factors frequently contribute to its development. HF is a major public health problem that affects more than 5 million individuals in the United States (Mozaffarian et al., 2016). With an aging population and improved survival after myocardial infarction, projections show that HF prevalence will increase by 46% from 2012 to 2030, resulting in more than 8 million patients with HF (Mozaffarian et al., 2016). The underlying cause of HF–related mortality is less likely to be cardiovascular disease and more likely to be non-cardiovascular diseases, such as pneumonia (Mozaffarian et al., 2016).

Health literacy is defined as “the capacity to obtain, communicate, process, and understand basic health information and services to make appropriate health decisions by patients” (U.S. Department of Health and Human Services, Office of Disease Prevention and Health Promotion, 2010, p. iii). According to the 2003 National Assessment of Adult Literacy (Kutner, Greenberg, Jin, & Paulsen, 2006), more than one third of adults have limited health literacy. A more recent national health literacy assessment from the Medical Expenditure Panel Survey (2011 to 2014) showed that patients who are older, less educated, and racial or ethnic minorities are more likely to have limited health literacy (Liang & Brach, 2017). Limited health literacy is more prevalent among HF patients (approximately 40%) than the general population in the United States (Cajita, Cajita, & Han, 2016). Limited health literacy results in more hospitalization and death among patients with HF (Wu et al., 2013).

As HF management is highly complex, it requires a patient's proactive involvement. Adequate understanding of instructions from health care professionals and self-care skills are essential to avoid adverse health outcomes (Riegel et al., 2009). Health literacy has received growing attention in recent decades (Koh et al., 2012). Mounting evidence has shown the significant impacts of limited health literacy on health care outcomes in general, and among older adults in particular (Baker, Parker, Williams, & Clark, 1998; Baker et al., 2007; Sudore et al., 2006). Several studies have identified that limited health literacy is independently associated with an approximately 50% to 100% increase in mortality in older adults (Baker et al., 2007; Sudore et al., 2006).

Limited health literacy may prevent patients from fully benefiting from education and disease management programs. The American College of Cardiology (ACC)/American Heart Association (AHA) advocate for basic fluid, diet, and medication management education for all patients with HF; this is a Class I recommendation (Yancy et al., 2013). Although results are still inconclusive, a recent meta-analysis by Jonkman et al. (2016) reported that a long duration of self-management education is likely to reduce mortality in patients with HF. Hospitalized patients are often overwhelmed by the enormous amount of information delivered during their discharge and immediate post-discharge period. Hospital staff arrange referrals, prescribe medications, and teach lifestyle modifications without assessing a patient's understanding of the information. This is known as “post-hospital syndrome,” first identified by Krumholz (2013) as a major barrier of improving care in patients recently discharged from the hospital. Post-hospital syndrome is particularly problematic among patients with low health literacy. In 2010, the Hospital Readmission Reduction Program (HRRP) and Affordable Care Act (ACA) were enacted (Centers for Medicare & Medicaid Services [CMS], 2018). The HRRP was designed to reduce hospital readmission (CMS, 2018). The ACA expanded health care access to underserved populations, including low-income adults (Sommers, Gunja, Finegold, & Musco, 2015). These cornerstone health care policy changes may help explain the inconsistent results regarding the association between mortality and limited health literacy in patients with HF and limited health literacy. Given the dynamic medical environment and the complexities of different post-hospital care policies, it is critical to better understand how limited health literacy influences mortality in patients with recent hospitalization due to decompensated HF. In addition, as there is an urgent demand for health literacy–based intervention programs, a systematic review of existing intervention studies is warranted.

Method

Search Strategy

Cohort Studies. Researchers searched relevant English-language articles in major databases that included PubMed®, ISI Web of Science, MEDLINE®/Ovid, Google Scholar, Cumulative Index to Nursing and Allied Health Literature, and Cochrane Database of Systematic Reviews, from their inception to April 3, 2018. In these six databases, researchers used combinations of terms to search cohort studies examining the effects of limited health literacy on mortality among patients with recent hospitalization due to decompensated HF. Searches included MeSH terms in PubMed. Search combinations included: (1) (heart failure OR congestive heart failure OR chronic heart failure OR heart decompensation) AND (2) (literacy OR health literacy OR knowledge OR instrument OR psychometry) AND (3) (hospitalization OR hospital stay OR decompensation) AND (4) (death OR mortality).

Intervention Studies. Researchers also searched studies examining interventions to improve self-care to evaluate the effects of health literacy on mortality among patients with HF. The following combinations were used: (1) (heart failure OR congestive heart failure OR chronic heart failure OR heart decompensation) AND (2) (literacy OR health literacy OR knowledge OR instruments OR psychometry) AND (3) (hospitalization OR hospital stay OR decompensation) AND (4) (death OR mortality) AND (5) (self-management OR self-care OR self-administration OR self-medication OR patient education OR education OR instruction OR behavior therapy) AND (6) (randomized controlled trial OR controlled clinical trial OR intervention studies OR intervention OR allocation).

Inclusion and Exclusion Criteria

Inclusion Criteria for Cohort and Intervention Studies. To investigate long-term associations, researchers included only cohort studies examining the effects of limited health literacy on mortality in adults ages 18 or older or adults with decompensated HF. Researchers also selected studies that followed patients for at least 1 year to examine long-term effects. In addition, researchers reviewed articles that tested the effectiveness of interventions designed to improve quality for self-management and lower mortality in patients with HF.

Exclusion Criteria of Cohort and Intervention Studies. Researchers excluded intervention studies that did not assess the health literacy of study participants. Researchers restricted the language to English and chose only studies that assessed health literacy with validated health literacy tools, such as the Test of Functional Health Literacy in Adults (TOFHLA; Baker, Williams, Parker, Gazmararian, & Nurss, 1999).

Study Selection and Data Extraction

Two authors (X.B.L., Y.A.) independently screened titles and abstracts. After an independent review, data from each study were transferred onto a standard sheet. For all phases, researchers discussed and resolved any disagreements using second opinions from two additional authors (M.J., H.Y.). Kappa statistics (κ) were computed to assess the inter-rater reliability of the screening phases: κ = 0.91 and κ = 0.82 for the cohort studies and randomized controlled studies, respectively. Researchers also searched through articles from bibliographies of the retrieved studies and review articles. When actual data were not presented, researchers directly contacted the corresponding authors to obtain missing data. As the selected studies had already been published elsewhere, the current study was exempt from Institutional Review Board approval. The study selection process is in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement, and is presented in Figure 1 and Figure 2 (Moher, Liberati, Tetzlaff, & Altman, 2009).

PRISMA study selection process for meta-analysis: Effects of limited health literacy on mortality among patients with recent hospitalization due to decompensated heart failure (HF).

Figure 1.

PRISMA study selection process for meta-analysis: Effects of limited health literacy on mortality among patients with recent hospitalization due to decompensated heart failure (HF).

PRISMA study selection process for systematic review: Effectiveness of health literacy interventions to improve quality in self-management and to lower mortality in patients with heart failure (HF).

Figure 2.

PRISMA study selection process for systematic review: Effectiveness of health literacy interventions to improve quality in self-management and to lower mortality in patients with heart failure (HF).

Quality Assessment

Researchers used the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) system (Guyatt et al., 2008) to assess the overall quality of evidence (Table 1). The overall quality of evidence took the following five domains into consideration: risk of bias, consistency, directness, precision, and publication bias. The GRADE rating system ranges from high to very low. Oxford Centre for Evidence-Based Medicine (2009) levels of evidence were used to assess the quality of evidence for each intervention study. These levels range from 1a (highest quality) to 5 (lowest quality).

Grading of Recommendations Assessment, Development, and Evaluation Quality of Evidence

Table 1:

Grading of Recommendations Assessment, Development, and Evaluation Quality of Evidence

Data Synthesis and Analysis

Study participants were divided into limited health literacy and other health literacy groups. Other health literacy was defined as marginal or adequate health literacy. In a meta-analysis of the cohort studies, researchers combined individual study results to calculate pooled odds ratio (OR) values and construct 95% confidence intervals (CI). Inter-study heterogeneity was assessed using Cochrane's Q test and I2 static values of 50% or higher, which indicate extensive inconsistency (Higgins & Thompson, 2002). The fixed-effect model was used because the Q statistic (p > 0.10) indicated low heterogeneity across studies (Higgins & Thompson, 2002). Publication bias was assessed using a visual inspection of funnel plots and Egger's regression analysis (Egger, Davey Smith, Schneider, & Minder, 1997). Researchers used optimal information size calculations as an objective measure of imprecision. A mortality risk increase of 100% caused by limited health literacy had an alpha = 0.05 and power = 0.80. This finding was based on Sudore et al. (2006), who attributed a two-fold mortality risk increase to limited health literacy. Researchers conducted sensitivity analyses by eliminating studies (n = 41) for which a confounding factor was associated with all-cause mortality. Researchers did not perform a meta-analysis of the intervention studies, as the interventions were not homogeneous, and the results of each study already showed that there was no relationship between intervention and mortality. Furthermore, there were too few studies to perform a meta-regression analysis. Therefore, the effects of important variables such as age, gender, and race/ethnicity could not be quantified. Instead, baseline characteristics from the pooled study participants were compared according to health literacy status (limited health literacy: n = 509; marginal or adequate health literacy: n = 2,349). All analyses were performed using the Comprehensive Meta-Analysis software Version 3 and SPSS version 24. A two-sided p value < 0.05 was considered statistically significant.

Results

Cohort Studies

A total of 3,448 patients were analyzed from three cohort studies (McNaughton et al., 2015; Moser et al., 2015; Peterson et al., 2011) examining the effects of limited health literacy on mortality in patients with recent hospitalization due to decompensated HF (Table 2). Approximately one in five (17.8%, 509/2,858) patients had limited health literacy. Two studies analyzed mortality in urban settings (McNaughton et al., 2015; Peterson et al., 2011), and one study analyzed mortality in a rural setting (Moser et al., 2015). All three studies showed a significant association between health literacy and mortality among HF patients. An analysis of baseline characteristics of pooled study participants according to health literacy status (Table A, available in the online version of this article) revealed that participants with limited health literacy were older (p < 0.01) and less educated (p < 0.01) than those with marginal or adequate health literacy. Figure 3 shows that limited health literacy increased mortality risk by 2.95 times (pooled OR = 2.95, 95% CI [2.34, 3.72], p < 0.01). Heterogeneity was moderate (Q = 3.80; p = 0.22; I2= 47.38%). A symmetrical funnel plot (Figure A, available in the online version of this article) and Egger's regression test showed no evidence of publication bias. No serious limitation was found in any domain. A level 1b rating applies because the study type was a randomized controlled trial in all three intervention studies used in this review. The current meta-analysis was conducted with data from selected observational cohort studies; therefore, the GRADE system rating started at a low level. Because follow-up periods were different across studies (1 to 2 years), a minor limitation in the inconsistency of follow-up periods was also raised. The overall quality of evidence was rated as low. A sensitivity analysis from the eliminated studies found that older age was significantly associated with all-cause mortality (p < 0.01).

Summary of Cohort Studies Examining the Effect of Limited Health Literacy on Mortality

Table 2:

Summary of Cohort Studies Examining the Effect of Limited Health Literacy on Mortality

Baseline characteristics of pooled study participants by health literacy status

Table A.

Baseline characteristics of pooled study participants by health literacy status

The effects of limited health literacy on mortality among patients with recent hospitalization due to heart failure: meta-analysis results.

Figure 3.

The effects of limited health literacy on mortality among patients with recent hospitalization due to heart failure: meta-analysis results.

Funnel plot of standard error by log odds ratio showing no evidence of publication bias.

Figure A.

Funnel plot of standard error by log odds ratio showing no evidence of publication bias.

Intervention Studies

A total of 1,330 patients were studied from three randomized controlled trials (Table 3) analyzing the effects of interventions on self-management and mortality in patients with HF, according to health literacy (De Walt et al., 2006; De Walt et al., 2012; Dracup et al., 2014). Interventions included face-to-face educational sessions and telephone-based support. All three clinical trials failed to show a significant relationship between interventions and mortality; these results were consistent across health literacy levels.

Interventions Designed to Improve Quality of Self-Management and Lower Mortality in Patients With Heart Failure (HF) by Health Literacy Level

Table 3:

Interventions Designed to Improve Quality of Self-Management and Lower Mortality in Patients With Heart Failure (HF) by Health Literacy Level

Discussion

To the best of the current researchers' knowledge, this meta-analysis is the first to examine the association between health literacy and mortality in patients with recent hospitalization due to decompensated HF.

Detailed explanations for how limited health literacy results in higher mortality among patients with recent hospitalization due to decompensated HF are yet to be identified. Based on current findings, age and education are key factors explaining the effects of limited health literacy on higher mortality (Kutner et al., 2006; Yamashita & Kunkel, 2015). These findings support the compression of mortality hypothesis, in which older age is associated with greater mortality, whereas greater educational attainment is linked to longevity (Brown et al., 2012).

It is possible that highly educated individuals are more likely to survive into advanced age and face a greater risk of mortality due to adverse health conditions such as HF. Although education and health literacy skills are known to be positively correlated with longevity, poor health conditions due to HF might negatively influence ability to read and write in older age (Federman, Sano, Wolf, Siu, & Halm, 2009). Findings from the current study should be verified with further meta-regression analyses, which were not feasible in the current study due to the limited number of studies in the review.

In the review of individual cohort studies, limited health literacy was associated with an increased risk of mortality across diverse study settings. Settings included a Colorado statewide health organization (Peterson et al., 2011), multistate rural areas (Moser et al., 2015), and a single academic hospital in Tennessee (McNaughton et al., 2015).

The TOFHLA is a widely used and comprehensive assessment tool, but it takes approximately 20 minutes to administer (Baker et al., 1999). The TOFHLA may not be suitable for a busy primary care setting. Alternatively, shorter self-administered tools such as the Brief Health Literacy Screen and the Rapid Estimate of Adult Literacy in Medicine are available (Chew, Bradley, & Boyko, 2004; Davis et al., 1993). Peterson et al. (2011) developed their own three-question tool to assess health literacy. Each of the cohort studies that the current researchers analyzed used different health literacy assessment tools. Therefore, development of a standardized health literacy assessment tool in primary care settings is needed.

In addition, most health literacy assessment tools are decades old and may not reflect the current health care environment (Baker et al., 1999; Haun, Valerio, McCormack, Sorensen, & Paasche-Orlow, 2014). Importantly, HF– specific self-care assessment tools have been validated and used in studies of patients with stable HF (Jaarsma, Strömberg, Mårtensson, & Dracup, 2003; Reilly et al., 2009; Riegel et al., 2009). However, their application is questionable in clinical settings where patients receive a tremendous amount of information from hospital-based health care professionals upon discharge (i.e., post-hospital syndrome) (Krumholz, 2013). Therefore, further development and application of easily administered HF–specific health literacy assessment tools are needed. It is not surprising that a series of studies have reported that age affects health literacy (Federman et al., 2009; Wu, Moser, DeWalt, Rayens, & Dracup, 2016; Yamashita & Kunkel, 2015).

Development of an optimal assessment tool is the first step to elucidate mechanisms of how limited health literacy could lead to higher mortality, and to clarify the roles of age and education in the same context.

In addition, specific components of health literacy should be examined in later life. Kobayashi, Wardle, Wolf, and von Wagner (2016) identified that older age had a greater impact on dynamic reasoning and numeracy skills, but a lesser impact on medical knowledge and vocabulary.

In a systematic review evaluating the ability of intervention to improve self-management and lower mortality in patients with HF according to health literacy, there was no correlation between intervention and mortality. Remote patient monitoring (RPM) care models for patients with HF have rapidly disseminated with advancements in communications technologies (Nakamura, Koga, & Iseki, 2014). Although the role of health literacy was not analyzed, a recent meta-analysis showed that RPM yielded lower mortality in patients with HF (Nakamura et al., 2014). Future research should evaluate the effects of RPM on mortality among patients with HF and limited health literacy. Telehealth programs offered by the Department of Veterans Affairs (2017) have expanded to serve 12% of Veterans in the United States. In fiscal year 2016, these programs reduced hospital admissions for chronic care management in patients residing in rural areas (Department of Veterans Affairs, 2017). There are now 33 states and the District of Columbia with insurance coverage laws for telehealth-based medicine (called “telehealth parity laws”). Payment parity does not relate to whether a service is covered; rather, payment parity governs how much the health plan will contribute toward paying for the covered service (Center for Connected Health Policy, 2017). If a state has payment parity, the health plan must pay the provider the same rates for telehealth services that it pays for in-person services. The cost and burdens imposed by telemedicine parity laws would likely exceed any benefits. In short, using telehealth technologies for patients with limited health literacy, particularly those with recent hospitalization due to HF, faces barriers to becoming fully implemented.

Limitations

Researchers acknowledge several limitations in the current study. Age possibly confounded the relationship between health literacy and health outcomes in analysis. Due to the small number of eligible studies, a meta-regression analysis was not feasible. Therefore, a causal relationship between limited health literacy and mortality could not be confirmed. All studies either excluded patients with cognitive impairment or did not categorize patients by cognitive impairment status (De Walt et al., 2006; De Walt et al., 2012; Dracup et al., 2014; McNaughton et al., 2015; Moser et al., 2015; Peterson et al., 2011). This exclusion of certain subpopulations may have created bias in the evaluated participant pool. The generalizability of the current study will remain limited until further studies can replicate its findings in diverse demographic settings. Researchers excluded studies that did not assess health literacy using validated tools. The strict criteria might have reduced the number of analyzed studies to a point where important trends were overlooked. Finally, patients in two of three analyzed studies were not from random samples, which may have introduced selection bias linked to patients with severe disease, for whom health literacy level (limited or other) could not be controlled (McNaughton et al., 2015; Peterson et al., 2011).

Conclusion

Health literacy plays a significant role in patients' ability to understand HF treatment and self-care. The current study found a negative association between health literacy and mortality. More efforts should be made toward changing policies and developing intervention programs to improve health literacy of patients with HF. In the upcoming era of the fourth industrial revolution, efforts should focus on the efficiency and safety of telehealth-based medicine, particularly in patients with HF.

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Grading of Recommendations Assessment, Development, and Evaluation Quality of Evidence

Quality AssessmentNumber of Patients Who DiedEffectsQuality
Number of StudiesStudy DesignRisk of BiasInconsistencyIndirectnessImprecisionPatients With Limited Health LiteracyPatients With Marginal or Adequate Health LiteracyRelative: Pooled OR (95% CI) (p < 0.001)Absolute: Limited vs. Other Health Literacy (95% CI) (p < 0.001)
3Observation cohort studiesNot seriousNot seriousNot seriousNot serious187 of 509 (36.7%)403 of 2,349 (17.2%)OR = 2.954 (2.344 to 3.722)≥208 per 1,000 individuals (155 to 264 more in limited literacy)⊕ ⊕ ○ ○LOW

Summary of Cohort Studies Examining the Effect of Limited Health Literacy on Mortality

StudyNFollow-Up PeriodStudy LocationInclusion CriteriaExclusion CriteriaHealth Literacy ToolsAll-Cause Mortality Rates by Health Literacy Groups
McNaughton et al. (2015)1,37920.7 months (median)Single academic hospital in TennesseeHospital discharge with primary diagnosis of HF (identified by ICD-9 codes)Discharge to post-acute facilities or home hospiceBrief Health Literacy Screen38.3% in limited health literacy, 26.5% in marginal or adequate health literacy, HR = 1.32 (95% CI [1.05, 1.66], p = 0.02)
Moser et al. (2015)575≥2 yearsRural areas in California, Nevada, and KentuckyHF hospitalization in the past 12 months and ability to read and write in EnglishLife expectancy ≤12 months, schizophrenia, impaired cognition, or concurrent participation in HF management programShort Test of Functional Health Literacy in Adults (S-TOFHLA)15.5% in limited health literacy, 14.6% in marginal health literacy, 9.9% in adequate health literacy, p = 0.001
Peterson et al. (2011)1,49415 months (median)Colorado statewide health care organizationPrimary hospital discharge of HF, ≥2 secondary hospital discharge diagnoses of HF, ≥3 emergency department visits with HF diagnosisNoneThree brief screening questionsa. Each question was scored by a 5-point scale.17.6% in limited health literacy, 6.3% in marginal or adequate health literacy, HR = 1.61 (95% CI [1.06, 2.43], p = 0.026)

Interventions Designed to Improve Quality of Self-Management and Lower Mortality in Patients With Heart Failure (HF) by Health Literacy Level

StudyNEligibility CriteriaInterventionsResults
Dracup et al.(2014)602Inclusion: (a) Rural California, Kentucky, and Nevada areas; town population <2,500 individuals or metropolitan population <50,000 individuals; (b) recent hospitalization within past 6 months for HF; and (c) age ≥18 years. Exclusion: Cognitive or vision impairment. Health literacy assessment: BHLSRandomized study group assignment (intervention vs. control). Face-to-face education session on self-care and follow-up telephone calls every 3 months up to 2 years.No significant improvement in cardiac death in intervention group. Results were unchanged in subgroup analysis by health literacy level.
DeWalt et al. (2012)605Inclusion: (a) Four metropolitan academic clinics; (b) NYHA Class II through Class IV in the past 6 months; and (c) current loop diuretic use. Exclusion: Not fluent in either English or Spanish or cognitive impairment. Health literacy assessment: S-TOFHLARandomized study group assignment (intervention vs. control). Both groups received a 40-minute in-person health literacy–sensitive training. The multisession group received five to eight follow-up telephone calls (10 minutes each).No significant difference in all-cause death. Results were unchanged in subgroup analysis by health literacy level.
DeWalt et al. (2006)123Inclusion: (a) Single metropolitan academic clinic, (b) clinical diagnosis of HF, and (c) NYHA Class II to Class IV within the past 3 months. Exclusion: Dementia, life expectancy ≤6 months, hearing impairment, blindness, current substance abuse, creatinine > 4 mg/dL or on dialysis, supplemental oxygen use, did not have access to a telephone, cardiac surgery or heart transplant candidate. Health literacy assessment: S-TOFHLARandomized study group assignment (intervention vs. control). The intervention group received a 1-hour education session and follow-up telephone calls. Follow-up period was 12 months. Control group received education material.No significant difference in all-cause death. Results were unchanged when health literacy level was added as modification factor.

Baseline characteristics of pooled study participants by health literacy status

VariablesLimited health literacy, n = 509Marginal or adequate literacy, n = 2,349P
Age: mean, standard deviation73.34, 13.5268.29, 12.93.015
Female: n, %228, 44.79%1104, 46.99%.412
Other than whites: n, %110, 21.61%397, 16.90%.301
High school graduation or higher: n, %377, 74.07%2114, 89.99%.008
Authors

Dr. Liu is Resident Physician, Department of Medicine, University of Arizona College of Medicine, Tucson, Arizona; Dr. Ayatollahi is Clinical Fellow and Dr. Jaradat is Clinical Fellow, Division of Cardiovascular Medicine, and Dr. Yoo is Assistant Professor, Department of Internal Medicine, University of Nevada Las Vegas School of Medicine, and Dr. Shen is Associate Dean, Dr. Lee is Visiting Scholar, Dr. Hwang is Visiting Scholar, Dr. Yeom is Research Assistant, and Dr. Upadhyay is Assistant Professor, School of Community Health Sciences, and Ms. Choi is Student, Honors College, University of Nevada Las Vegas, Las Vegas, Nevada; Dr. Yamashita is Associate Professor, Department of Sociology, Anthropology, and Health Administration and Policy, University of Maryland Baltimore County, Baltimore, Maryland; Dr. Kim is Assistant Professor, Department of Health Administration, Soonchunhyang University, Asan, Korea; and Ms. Liu is Student, Northeastern University, Boston, Massachusetts. Dr. Lee is also Associate Professor, Department of Family Medicine, Yonsei University College of Medicine, and Dr. Hwang is also Associate Professor, Department of Thoracic and Cardiovascular Surgery, Korea University College of Medicine, Seoul, Korea. Dr. Liu and Dr. Ayatollahi contributed as lead authors.

The authors have disclosed no potential conflicts of interest, financial or otherwise. Dr. Yoo is supported by the faculty career development award from University of Nevada School of Medicine, Las Vegas, Nevada, and Dr. Kim is supported by Soonchunhyang University, Asan, Korea.

Address correspondence to Ji Won Yoo, MD, MS, Assistant Professor, Department of Internal Medicine, University of Nevada Las Vegas School of Medicine, 1701 West Charleston Boulevard, #230, Las Vegas, NV 89102; e-mail: ji.yoo@unlv.edu.

Received: April 04, 2018
Accepted: August 17, 2018
Posted Online: December 13, 2018

10.3928/19404921-20181018-01

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