Identifying elderly at greatest risk of inadequate health literacy: A predictive model for population-health decision makers

Abstract

Background

Despite concern that inadequate functional health literacy (FHL) is a widely prevalent problem and is associated with a variety of adverse health consequences, there is an absence of tools that population-health decision makers can use to efficiently identify those at risk of inadequate FHL.

Objectives

The objective of this study was to develop and validate a predictive model for estimating FHL in the elderly, generate a national estimate of FHL, and assess the construct validity of the national estimate.

Methods

Using data from the largest study of FHL in the elderly, a multiple regression model to estimate FHL was developed and validated using common demographic predictors. Subsequently, the model was used to estimate FHL in the 65-year or older subgroup of the 1992 National Adult Literacy Survey (NALS). Construct validity of the FHL estimate was assessed by evaluating the direction, magnitude, and significance of association with reported general functional literacy (GFL) proficiency in the 1992 NALS.

Results

A 20-variable model was derived (R² = 0.365). The model correctly classified 73.2% of the sample into the appropriate FHL category. National prevalence of inadequate and marginal FHL was estimated to be 39.2% and 5.2%, respectively. FHL was significantly correlated with prose, document, and quantitative dimensions of GFL at r = 0.58 or higher (P < .0001).

Conclusions

This study was the first to quantitatively model and substantiate the high national prevalence of inadequate FHL in the elderly. The proposed quantitative model can be used in subsequent research to efficiently risk-stratify individuals by FHL level in large data sets to assess the relationships between FHL and health status, utilization, expenditures, and satisfaction. Furthermore, the model can be used to identify individuals at high risk of inadequate FHL, which will enable targeting of educational interventions that address FHL deficiencies.

Introduction

The increasing complexity of the health care system places greater cognitive demands on patients than ever before. Understanding complex health and prescription drug benefits and obtaining necessary acute and preventive care requires navigating a system that requires a high level of understanding of written and numeric information. In its landmark report about disparities in health care, the Institute of Medicine (IOM) expert committee concluded that “…low literacy skill is a significant obstacle to full access to effective medical care.”¹ The American Medical Association has recognized that adequate functional health literacy (FHL) is fundamental to the efficient use of the healthcare system for patients, providers, and payers.² In addition, Healthy People 2010 has incorporated the improvement of health literacy for persons with inadequate or marginal literacy skills as an objective.³

FHL can be defined as “…the constellation of skills, including the ability to perform basic reading and numerical tasks required to function in the health care environment.”² Focusing on health-specific tasks, FHL is conceptually distinct from the broader concept of General Functional Literacy (GFL) which is “…using printed and written information to function in society, to achieve one's goals, and to develop one's knowledge and potential.”⁴ GFL provides the necessary foundation of skills for FHL. It is hard to imagine a person with low GFL functioning with a high level of skill in the health care setting. Although expected to be closely associated with one another, GFL is a necessary but not sufficient precursor set of skills for FHL. The 1992 National Adult Literacy Survey (NALS) estimated that approximately 90 million adult Americans performed at the 2 lowest levels of GFL.⁴ The 1992 NALS tested skills across an increasingly complex continuum of tasks fundamental to adequately functioning in society. The tasks were grouped into 3 distinct dimensions (ie, prose, document, and quantitative literacy). With the emphasis on completion of practical, “real world” tasks, rather than on norm-referenced grade-level achievement, the 1992 NALS was the first nationally representative assessment of GFL in the United States. The 1992 NALS results represent the national prevalence of prose, document, and quantitative dimensions of GFL proficiency. Individuals at greatest risk for low GFL were poor, older, members of a racial minority group and had lower levels of education. The 1992 NALS did not address FHL and to date, no effort has been made to assess the relationship between FHL and GFL.

A subsequent national survey of GFL, the 2003 NALS, did incorporate health-related prose, document, and quantitative tasks.⁵ Preliminary results from the 2003 NALS have reported similar prose and document literacy proficiency to the 1992 NALS and a slight, but statistically significant, improvement in quantitative literacy scores.⁶ To date, results related to health literacy from the 2003 NALS have not been released.

FHL measurement has shifted from a focus on the readability of passages to an individual's ability to read, comprehend, and act on what is written.⁷ Suboptimal FHL has been associated with lower understanding of chronic disease and its management.8, 9 Compounding this problem is poor patient-provider communication reported by patients with inadequate FHL.¹⁰ A sense of shame associated with inadequate FHL may further widen the patient-provider communication gap.¹¹ Individuals often hide this inadequacy and may be reluctant to pursue deeper inquiry into their disease condition and management. Finally, problems associated with poor health literacy may be exacerbated in the elderly because increasing age has been associated with decreasing FHL skills.¹²

During the 1990s, instruments were developed to measure FHL skills related to reading comprehension and numeracy. These instruments were used to describe the prevalence of inadequate, marginal, and adequate FHL in 2 distinct population subgroups: (1) adult patients who used urban, public hospitals, and (2) Medicare managed care enrollees (ie, Medicare Health Literacy Study [MHLS]).13, 14 The findings from these 2 studies documented that 25%¹⁴ to 29%¹³ of study participants had inadequate FHL and 11%¹⁴ to 14%¹³ of participants had marginal FHL. Although it is limited by regional sampling from 4 sites in 1 Medicare managed care plan, the MHLS¹⁴ study of 3260 Medicare managed care enrollees is the largest and most comprehensive study to date that can be used to derive predictive models for FHL in the elderly.

The body of research into the prevalence and consequences of low health literacy was recently summarized in evidence-based reviews by the Agency for Healthcare Research and Quality (AHRQ) and the IOM.15, 16 In general, both reviews acknowledge that poor literacy is a widely prevalent problem associated with a variety of adverse health consequences. However, an alternative comprehensive literature review concluded that the current body of literature evaluating the prevalence of limited health literacy could not “…provide a nationally representative prevalence estimate.”¹⁷ The AHRQ and IOM reviews called for more uniform measures of FHL, increased rigor in the evaluation of interventions that address the FHL deficiencies, and a more active approach to measuring FHL in health care systems among their many recommendations to address the limitations in the current body of literacy research.

Current strategies for directly measuring FHL are time consuming and are not conducive to creating a shame-free environment in busy health care settings such as pharmacies, clinics, and physicians' offices. Given the complexity and demand of measuring FHL at the individual level, there is no simple method for pharmacist practitioners, pharmacy managers, and population-health decision-makers such as pharmacy benefits administrators to use to efficiently identify those at risk of inadequate FHL in order to target appropriate educational interventions. An alternative strategy for identifying at-risk individuals is to use current research to generate a valid and reliable statistical model for FHL from commonly available demographic characteristics. To have broad applicability, the model must be capable of being used across a variety of administrative, practice, and research settings. By using a model derived from commonly available demographic characteristics to estimate FHL level, the practitioner, manager, and administrator can efficiently identify individuals at risk for inadequate or marginal FHL in a shame-free way.

In an effort to address gaps in the FHL literature, the objectives of this study were to (1) develop and validate a statistical model for estimating the prevalence of FHL using commonly available demographic characteristics, (2) apply the statistical model to estimate the national prevalence of inadequate and marginal FHL, and (3) assess the relationship between GFL and the estimate of FHL to establish the construct validity of the FHL estimate.