Health Literacy: An Overlooked Factor in Understanding HIV Health Disparities

Introduction 

Recent studies have suggested that limited literacy in adults may contribute to racial disparities in health.1, 2, 3 This is important, as reducing disparities in health care is one of the two primary federal goals for public health in the United States.4, 5 According to the Institute of Medicine (IOM), 90 million people in the U.S. lack the literacy proficiency needed to properly understand and act on health information.6 This has often been referred to as health literacy, a reflection of both a patient’s ability and the literacy prerequisites of the healthcare system.7 Although limited health literacy has been associated with poorer health outcomes, and also has been shown to be more prevalent among African Americans than whites,1, 2, 3, 8, 9 it is unclear whether racial differences in health literacy explain the presence of health disparities.

In the context of HIV, individuals with low literacy skills have been more likely to possess a poor working knowledge of their disease and its treatment.10, 11, 12, 13, 14, 15 Kalichman et al. 10, 11 found that infected patients with limited literacy had less general knowledge of the disease and their own treatment compared to patients with adequate literacy, and that they were less likely to have an undetectable viral load. While Paasche-Orlow et al.16 found no association between health literacy and HIV-medication adherence or viral load suppression, Wolf et al.15 found that patients with low literacy were more than three times as likely to be nonadherent to their anti-retroviral regimens than those with adequate literacy.

The HIV literature also documents substantial racial disparities in health outcomes. Most noteworthy, African Americans with HIV infection are at greater risk for a faster progression to AIDS and shorter survival in comparison to whites.17, 18 Racial differences in medication usage contribute to disparities in health outcomes.19, 20, 21 Possible explanatory factors have been offered, including variability in access to medication22, 23 and adherence practices.6, 24 Although health literacy and race are independently associated with medication adherence,25 it is unclear to what extent health literacy might be an underlying mechanism that promulgates racial differences in HIV-medication adherence.

Recent studies have suggested that health literacy is a more powerful predictor of health status than race.1, 2, 3 What has yet to be presented are mediating analyses exploring health literacy as a determinant of racial differences in the performance of health-promoting behaviors, such as medication adherence. As such, the objective of this study was to examine the mediating effect of health literacy on the relationship between race and HIV medication adherence.

Methods 

Results 

Respondents had a mean age of 40.1 years (SD=9.2 years), 79.9% were male and 45.1% were African American. More than half (55.9%) of respondents were unemployed, 39.7% had an annual household income less than $10,000, and 52.9% were either covered by Medicaid or did not carry any health insurance. Over 60% reported at least some college education. Approximately one third had either low or marginal literacy skills; 11.3% were reading at or below a 6th-grade level (low literacy), and 20.1% were reading at a 7th- to 8th-grade level (marginal literacy). More than half (52.5%) of all patients were also receiving treatment for a non–HIV-related chronic illness. Nearly one third reported receiving mental health services, and 9.3% had received treatment for alcohol or illicit drug use in the past 6 months. Over 70% were taking three or more HIV medications. Demographic and clinical characteristics are shown in Table 1.

Table 1. Sociodemographic characteristics of patients (N=204)

	Variable	Percentage
	Race
	Black	45.1
	Gender
	Male	79.9
	Age group
	<40	58.8
	40–49	28.4
	≥50	12.6
	Education
	<High school	12.3
	High school graduate	26.0
	>High school	61.8
	Literacy level
	≤6th grade (Low)	11.3
	7th–8th grade (Marginal)	20.1
	≥9th grade (Adequate)	68.6
	Annual income
	<$10,000	39.7
	$10,000–$11,999	23.0
	$12,000–$17,999	9.8
	≥$18,000	27.5
	Insurance
	Private	27.5
	Medicare	19.6
	Medicaid or free care	52.9
	Employment
	Unemployed	55.9
	Employed, part-time	15.2
	Employed, full-time	28.9
	Number of HIV medications in regimen
	1–2 medicines	29.9
	≥3 medicines	70.1
	Non-HIV comorbid conditions
	≥1 non-HIV comorbid conditions	52.5
	Mental illness
	Treated in past 6 months	29.9
	Drug or alcohol abuse
	Treated in past 6 months	9.3

African-American patients were more likely to possess marginal or low literacy skills compared to non–African-American patients (52.1% vs 14.3%, p<0.001), and were significantly less likely to self-report adherence to their medication regimens in the past 4 days (60.1% vs 76.8%, p=0.014). Patients with low literacy were more likely to be nonadherent (52.2%) than patients with adequate literacy (30.0%, p=0.01).

To confirm the association between race and the potential mediating variable (literacy), a preliminary regression model was analyzed with African-American race as the independent variable and low literacy skills as the dependent variable, controlling for age and study site. A significant association between African-American race and low literacy was confirmed (adjusted odds ratio [AOR]=7.4, 95% confidence interval [CI]=1.49–10.9). For Model 1 examining race and medication adherence, African Americans were 2.40 (95% CI=1.14–5.08; C statistic=0.67) times more likely to be nonadherent to their HIV-medication regimen than non–African Americans (Table 2). As illustrated in Table 2, when literacy was included in the second model, the effect estimates of African-American race diminished by 25% to a point of nonsignificance (AOR=1.80, 95% CI=0.51–5.85; C statistic=0.72). Low literacy remained a significant independent predictor of nonadherence (AOR=2.12, 95% CI=1.93–2.32). Older age and a greater number of medicines in the patient’s regimen were also significantly associated with a greater likelihood of missed doses. Patients with an annual income below $10,000 and those also receiving treatment for a non-HIV comorbid condition were less likely to self-report missed doses in the past 4 days.

Table 2. Multivariate regression analysis for nonadherence to HIV-medication regimens, with and without literacy level

		Model 1		Model 2
		AOR	95% CI	AOR	95% CI
	Race
	White	1.00		1.00
	Black	2.40	1.14–5.08	1.80	0.51–5.85
	Gender
	Female	1.00		1.00
	Male	0.94	0.84–2.01	0.97	0.80–1.18
	Age group
	<40	1.00		1.00
	40–49	1.29	0.64–2.02	1.29	0.61–2.79
	≥50	1.48	1.09–5.99	1.52	1.33–1.72
	Annual income
	≥$18,000	1.00		1.00
	$12,000–$17,999	2.26	1.20–1.53	2.19	0.80–6.05
	$10,000–$11,999	1.36	0.94–5.47	1.10	0.64–1.90
	<$10,000	0.42	0.19–0.93	0.45	0.45–0.78
	Number of HIV medications in regimen
	1–2 medicines	1.00		1.00
	≥3 medicines	1.24	1.17–1.32	1.26	1.12–1.32
	Non-HIV comorbid condition
	No	1.00		1.00
	Yes	0.74	0.66–0.82	0.70	0.63–0.78
	Mental illness
	No prior treatment	1.00		1.00
	Treatment in past 6 months	1.31	0.68–2.47	1.11	0.66–2.59
	Literacy level
	≥9th grade (adequate)	–		1.00
	7th–8th grade (marginal)			1.55	0.93–2.45
	≤6th grade (low)			2.12	1.93–2.32
	Model fit (C statistic)	0.68		0.74

AOR, adjusted odds ratio; CI, confidence interval.

Discussion 

Understanding the reason for pervasive health disparities across race and ethnicity is a major research, practice, and policy goal in the U.S.33, 34 To provide new insights into the pathways that lead to health disparities, patients were recruited from two U.S. regions to examine whether health literacy mediates race disparities in HIV-medication adherence. It was found that African-American patients had a twofold greater likelihood of being nonadherent to their anti-retroviral regimens. Yet consistent with predictions, the inclusion of health literacy reduced the explanatory power of race. In the final model, health literacy, not race, significantly predicted nonadherence. It is believed that this study is the first to examine health literacy as a mediator of race for HIV-medication nonadherence.

While the association between race and medication adherence was reduced by 25% once literacy was entered in the model, clearly other factors contributed to racial disparities. In this study alone it was found that treatment-related aspects of regimen complexity and comorbidity independently predicted adherence, as did age and income. Interestingly, patients with the lowest annual household income or those who were contending with a non-HIV comorbid condition were more likely to be adherent than patients with higher household incomes or those without a non-HIV comorbidity. While these relationships were not entirely clear, it is possible that individuals with the least amount of financial resources were being identified by the healthcare system as being at high risk and subsequently intervined upon. This also could be true for those with greater comorbidity, although it is important to note that only medication-taking behaviors were assessed and not health status or actual treatment outcomes. Future studies should seek to investigate in more detail the role of other patient psychosocial characteristics, such as culture and social support, as possible mediators of the now well-established relationships among literacy, health behaviors, and outcomes.6, 35

Certain limitations to the study should be acknowledged. First, adherence could not be assessed using one or a combination of other more objective measures, such as random pill counts, Medical Equipment Management Systems (MEMS) caps, or pharmacokinetic laboratory assessments. Although an existing, validated assessment tool was used to measure HIV-medication adherence,26, 27 through questionnaires patients might have underreported missed doses. However, several recent studies have concluded that self-reported measures, such as the PMAQ, are viable and accurate means to measure adherence.20, 36 Second, these data were derived from a cohort of HIV-infected patients interviewed 5 years ago, and might not reflect directly the experience of those on more current HIV-medication regimens. While more recent advances offer the potential for simplified and less restrictive dosing schedules, adherence still remains a significant challenge for patients with the disease.37, 38 Therefore, it is believed that these findings are relevant to the present day. Despite these limitations, this study is the first to assess the impact of limited health literacy in explaining racial/ethnic differences in medication adherence among a sample of patients from both urban and rural settings.

Limited health literacy presents a wide-reaching barrier to disease prevention that, unlike race/ethnicity, is potentially modifiable, which is why this study has important policy implications, particularly with respect to the development of communication strategies to promote HIV-medication adherence that are proven to be effective with patients of all literacy levels. Most health education materials describing medication management and adherence have been written at the high school or college level and may be difficult to understand by individuals with low literacy skills.39 The development of educational strategies that are both appropriate for lower-literacy audiences and culturally sensitive may benefit the large number of patients who are at risk of nonadherence.15, 40, 41, 42, 43 The design of better medication instructions for patients with more-limited literacy, such as improved packaging, labeling, and dispensing practices, is sorely needed.44 Instructional and educational improvements such as these may help decrease the racial disparities in medication adherence; and, ultimately, contribute to reducing disparities in the early development of AIDS and AIDS-related mortality.