http://orcid.org/0000-0003-0299-4582
Abstract
Limited health literacy (HL) is associated with a lower medication adherence in patients with chronic obstructive pulmonary disease (COPD). In this study, we examined the potential mitigating role of caregiver support on the relationship between HL and adherence to COPD medications. We conducted a prospective observational study of adults with COPD and their caregivers. HL was assessed using the Short Test of Functional Health Literacy in Adults (S-TOFHLA) and COPD medication adherence was evaluated with the Medication Adherence Rating Scale (MARS). We also collected caregiver HL data for a subset of participants. We tested whether having a caregiver impacted the relationship between HL and medication adherence using cross-sectional data collected between 2011 and 2015. Our sample included 388 COPD patients and 97 caregivers. COPD patients with low HL had a lower medication adherence (odds ratio [OR]: 0.44, 95% confidence interval [CI]: 0.24–0.81) after adjusting for sociodemographic factors. Caregiver presence was not associated with increased patient medication adherence (OR: 1.28, 95% CI: 0.79–2.08). Among the subset of patients with caregivers, low patient HL remained associated with a lower medication adherence (OR: 0.28, 95% CI: 0.09–0.82) when adjusted for caregiver HL and sociodemographic factors. Low HL is associated with lower COPD medication adherence, and this effect is not mitigated by the presence of a caregiver. These findings suggest a need for effective strategies to manage high-risk COPD patients with low HL, even among those with adequate support from caregivers, and to design interventions for both patients and caregivers with low HL.
Introduction
Following a consistent medication regimen is a critical component of disease management for patients with chronic obstructive pulmonary disease (COPD). Long-acting bronchodilators (LABA) and inhaled corticosteroids (ICS) prescribed for daily use are the cornerstones of COPD treatment and reduce the risk of exacerbations [Citation1]. A clear understanding of how to use these medications and the importance of daily use is therefore essential for disease control and better quality of life. Unfortunately, previous studies have found that up to 72% of patients with COPD do not take their medications as prescribed by their healthcare providers [Citation2], and that socioeconomically disadvantaged patients, in particular, have low adherence to inhaled medications [Citation3].
Low health literacy (HL) is a major barrier to ICS and LABA adherence among COPD patients. HL has been defined as an individual’s ability to understand written or spoken healthcare information to make appropriate health decisions [Citation4], and is a critical factor in designing interventions to support medication adherence and other self-management behaviors (SMB). Low HL has been widely documented to have a negative association with medication adherence [Citation5]. Several mechanisms may underlie this association, including limited understanding by patients of the written and verbal medication use instructions they receive from their healthcare providers and which accompany their inhalers [Citation6]. The problem of low HL is of particular concern for COPD patients because many experience cognitive impairment from their disease, and moreover because COPD affects a mostly elderly population who may suffer cognitive decline due to aging and other health conditions. Cognitive functioning is directly associated with HL [Citation7,Citation8].
Support from caregivers, such as family members or friends, may mitigate self-management challenges among low-HL COPD patients. Caregivers may provide tangible help, such as assistance with healthcare-related tasks, as well as emotional and informational support and companionship, which could indirectly impact health outcomes [Citation9]. Throughout the literature, there is evidence that caregiver support can mitigate patients’ health-related stress [Citation10], improve self-management of chronic illness, and positively affect long-term outcomes in conditions such as COPD [Citation11,Citation12]. Thus, caregivers may be able to help patients with low HL overcome the challenges they face adhering to COPD medications.
Despite a substantial body of evidence on the importance of HL in determining health outcomes, few studies have examined caregivers’ HL and its association with the health costs and outcomes of older adults [Citation13] and particularly older adults with chronic illness [Citation14]. Among the literature that does exist on this topic, preliminary results have raised concerns about the capacity of caregivers to support older patients with low HL. A 2018 systematic review of the literature on caregiver HL identified only three studies which focused on caregivers of older adults. One study in this review found that over one-third (36%) of paid caregivers had inadequate HL; caregivers with low HL incorrectly interpreted prescription medication instructions more often than those with adequate HL [Citation15].
The present study explores the role of caregivers and caregiver HL in medication adherence among older COPD patients. We hypothesized that the presence of a caregiver would mitigate the impact of low patient HL on medication adherence, especially if the caregiver had adequate HL.
Methods
Settings and subjects
We conducted an observational study of English- and Spanish-speaking adults with COPD from primary care practices serving socioeconomically and racially diverse communities in New York City, NY and Chicago, IL. Participants were recruited in these practices from November 2011 to January 2015 and were considered eligible if they were community dwelling, ≥55 years of age, had a previous diagnosis of COPD, and spoke English or Spanish. We excluded patients with asthma or other chronic respiratory illness, or dementia, either diagnosed by a medical provider or as determined by a brief cognitive screener.
We also recruited primary caregivers for all patients who reported having one and met the inclusion criteria for patient–caregiver dyads. As many caregivers do not self-identify with this role, but view the support provided as part of familial expectations [Citation16], caregivers were defined as any unpaid or paid individual who provided assistance to the patient, accompanied them to medical appointments, or helped make medical decisions. Caregivers were eligible for the study if they were 18 years or older and had served as the patient’s primary caregiver for ≥6 months at the time of recruitment.
Potential participants were identified through the electronic medical records and clinic registration systems of participating clinics. Trained, bilingual research assistants contacted potentially eligible patients by telephone and administered a brief eligibility screener. If eligible, participants were scheduled for an in-person interview, at which time formal consent was obtained. All participants and caregivers were asked to read and sign a written informed consent form in either English or Spanish.
Power calculations showed that for 400 subjects, analyses would have >80% power to detect a 25% difference in medication adherence between patients with and without caregivers at the p < 0.05 level (two-tailed). Additionally, we estimated that with 100 caregivers, the study would have 84% power to detect 30% difference in rates of adherence among patients with high and low literacy caregivers.
The study was conducted in accordance with the amended Declaration of Helsinki, and was approved by the institutional review boards of the Icahn School of Medicine at Mount Sinai (protocol # HS11-01325) and the Northwestern University Feinberg School of Medicine (protocol # STU00051862).
Measures
The HL of patients and caregivers was assessed using the Short Test of Functional Health Literacy in Adults (S-TOFHLA). The S-TOFHLA is comprised of a 36-item reading comprehension section and a 4-item numeracy exercise and has been validated in both English- and Spanish-speaking populations [Citation7,Citation17]. The score range is 0–36 and scores below 23 have been validated as indicating low HL [Citation18].
We assessed COPD medication adherence by self-report using the Medication Adherence Rating Scale (MARS) [Citation19], a validated scale (English and Spanish) specifically worded to avoid social desirability bias [Citation20]. We defined adequate medication adherence as a MARS score of ≥4.5 [Citation19].
All demographic variables, including age, race, ethnicity, and household income, were assessed by self-report. Co-morbidities, including gastroesophageal reflux (GERD), hypertension, diabetes, congestive heart failure, depression, anxiety, osteoporosis, arthritis, hepatitis, and chronic kidney disease were self-reported by participants and then verified through the electronic medical record. COPD severity was calculated using the COPD Severity Score, a validated survey measure for which a score of ≥15 indicates severe COPD [Citation21].
Statistical methods
We used the t-test and chi-square test to compare baseline characteristics by HL status. We examined the unadjusted association between patient HL and medication adherence in the full cohort (n = 388). We then fitted binary logistic regression models to determine whether the association of low HL with adherence was modified by the presence of a caregiver. We first tested a model including terms for the patient’s HL and presence of a caregiver. In the second model, we also included an interaction term between these terms, in order to test the hypothesized role of caregiver presence in modifying the effect of HL on medication adherence. We then conducted a third, adjusted model controlling for sex, race/ethnicity, age, household income, and COPD severity, which were expected to be potential confounders based on the conceptual model.
We fitted a logistic regression model for the subgroup of patients with caregivers (n = 97) to determine whether caregiver HL is associated with patient medication adherence. As with the full cohort analysis, the first model included patient HL and caregiver HL, the second model included an interaction term between patient and caregiver HL, and the third model was adjusted for sex, race/ethnicity, age, household income, and COPD severity.
All analyses were performed using SAS statistical software (SAS Institute, Cary, NC).
Results
We identified 1,132 potentially eligible patients through the electronic health record and received permission from their primary care physicians to approach them via letter and phone follow-up. We successfully contacted 927 patients who were eligible based on their medical records and screened 618 of them; 482 were eligible for the study, and 403 (43%) agreed to participate. The baseline interview was completed by 393 patients, and 388 patients completed the S-TOFHLA and were included in the analyses. Of those excluded from analysis, four could not read and one refused to complete the S-TOFLHA. We identified and consented caregivers of 105 enrolled participants who reported receiving assistance in managing their health. Of these caregivers, 97 completed the S-TOFHLA, whereas one was legally blind, one could not read and six refused or ran out of time to complete the S-TOFHLA.
Overall, 117 (30%) COPD patients had low HL. Compared with those with adequate HL, patients with low HL were older (mean 69.9 [8.6] years vs. 67.2 [8.0] years, respectively), less likely to be married, and had more limited English proficiency, less education, and lower household monthly income (p < 0.05 for all comparisons; ). Characteristics of the sub-group with caregivers are summarized in . The cohort had a robust minority racial/ethnic representation: among patients with low HL, 53% were African-American non-Hispanic and 28% were Hispanic, and among patients with adequate HL 40% were African-American non-Hispanic and 11% were Hispanic (p < 0.001). Low HL patients were also more likely to have co-morbid diabetes, hypertension, congestive heart failure and/or depression (all ps < 0.001). Additionally, patients with low HL were more likely to report having a caregiver than those with adequate HL (55% vs. 40%, p = 0.005).
Table 1. Characteristics of patients by health literacy level.
Table 2. Characteristics of patients with caregivers by medication adherence.
In the full cohort (n = 388), patients with low HL were less likely to be adherent to their COPD medications than patients with adequate HL (25% vs. 45%, respectively). Logistic regression showed a significant association between low patient HL and medication adherence (odds ratio [OR]: 0.40, 95% confidence interval [CI]: 0.24–0.68, ). Presence of a caregiver was not significantly associated with medication adherence (p > 0.05). In adjusted analysis, low HL maintained its significant association with medication adherence (OR: 0.44, 95% CI: 0.24–0.81, ). The interaction term for patient HL and the presence of a caregiver was not statistically significant (p > 0.05).
Table 3. Associations of health literacy and caregiver support with medication adherence, unadjusted and adjusted (N = 330).
In the subgroup of patients who had caregivers (n = 97), patients with low HL had significantly lower odds (OR: 0.29, 95% CI: 0.12–0.72) of adequate adherence to their COPD medications. The association between low HL and medication adherence persisted in adjusted analyses (OR: 0.28, 95% CI: 0.09–0.82, ). The interaction of caregiver and patient HL was again not statistically significant (p > 0.05).
Table 4. Association of medication adherence, health literacy, and caregiver support among participants with caregivers, unadjusted and adjusted (N = 94).
Discussion
Social support and caregiver involvement in chronic disease management are relatively well established as predictors of better health outcomes [Citation22]. One review found that out of seven studies, five showed positive associations between social support and SMB and/or self-efficacy to manage one’s illness [Citation23]. However, in this study, we did not find a mitigating impact of caregivers on the association between low HL and a lower medication adherence. We instead found a strong association between low HL and medication adherence, which persisted among patients who had the support of a caregiver. Moreover, in the subset of patients with caregivers, low patient HL was related to a lower medication adherence, regardless of caregiver HL level. These findings suggest that overcoming low HL is a critical target area for interventions to improve medication adherence and COPD outcomes, and that while caregivers play a role in health management for some COPD patients, even those with support are at risk for poor outcomes if they have low HL.
As in prior studies, we found that a large percentage of COPD patients had low adherence to their medications [Citation24,Citation25]. We previously reported on the relationship between low HL, illness beliefs and medication adherence in older adults with COPD: individuals with low HL were less likely to believe in the permanence of their COPD and more likely to express concern about taking their COPD medications, both of which predicted a lower medication adherence [Citation25]. The finding that the association between low HL and low medication adherence in patients with COPD is not mitigated by the presence of a caregiver raises new concerns about the role of caregivers in influencing patient behaviors for COPD management.
Previous research has shown that SMB for chronic disease is often impacted by the attitudes and beliefs toward health as well as the functional support, or helping actions such as reminders to take medication, provided by their social network [Citation12]. If HL is limited for the patient, the caregiver, or both, this may complicate the traditional view that greater social support and care provision will improve SMB for older patients with chronic illness, with critical implications for clinical practice. For patients with caregivers who accompany them to appointments, providers may feel reassured that they can rely on the caregiver to ensure the patient receives proper disease management; however, our results suggest that this strategy may lead to suboptimal SMB unless providers also consider the patient’s HL level. Alternative approaches such as additional education by physician extenders, care managers or community-based coaches may help in educating low literacy patients and their caregivers and supporting self-management. It is also important to include both patients and their caregivers in care planning.
The null finding for the role of caregivers and caregiver HL in the pathway between patient HL and self-management is supported by other studies. One paper reports that among older adults with low HL, social support was not associated with physical or mental health, whereas in the high HL group, social support was positively associated with several health status measures [Citation26]. Similarly, another study found that social support was associated with a higher medication adherence for patients with adequate HL, but not those with limited HL [Citation27].
Our results add to the literature highlighting the need to support medication adherence of low HL patients with COPD. These findings suggest that SMB materials for this population should be designed to support understanding by low-literacy patients as well as caregivers, such as multi-modal communication (e.g., verbal and print), and optimized formatting of print materials (e.g., low reading grade level, single idea per line) [Citation28–30]. Additionally, the majority of social support studies are conducted among white, mid-to-high socioeconomic status, middle-aged men; very few have been conducted with older racially and ethnically diverse adults such as our sample. Future research should further investigate the association between HL and SMB in chronic disease patients with caregivers from diverse sociodemographic backgrounds, in order to better understand the circumstances under which behaviors are impacted more by HL than the presence of social support. If the findings of the present study represent a larger pattern, interventions for low-HL patient populations should explore how both patients and caregivers can be involved in health education, and whether it is possible to use the strengths of a patient–caregiver relationship to overcome the disadvantage of low HL.
Our study has strengths and weaknesses that are worth noting. First, this analysis was conducted from a prospective cohort of 388 patients and 97 caregivers, providing a large sample with measures of HL and other variables. Second, most patients in the study were racial and ethnic minorities and of low income, representative of urban settings where the burden of low HL and poorer COPD outcomes are most critical. However, our definition of “caregiver” was broad, which may have contributed to the null findings. The study did not differentiate between informal caregivers, such as friends and family, and formal, paid caregivers, and thus we could not explore potential heterogeneity in their influence on COPD SMB. This difference in role may also account for the lack of a significant association between caregiving and medication adherence, as an informal caregiver may not have the same involvement in the patient’s healthcare as would a paid caretaker. We also did not assess the caregivers’ level of engagement in the patients’ healthcare, such as whether they attend medical appointments with the patient or only assist with SMB in the home. Moreover, the findings are only generalizable to older adults in an urban US setting. Finally, with only 97 patients with an identifiable caregiver, the power of the subgroup analysis was limited.
In summary, low HL among patients with moderate to severe COPD is associated with decreased medication adherence. However, in this study, support from caregivers was not associated with a better medication adherence among patients with low HL.
Declaration of interest
No conflicts of interest exist for the following authors: Kimberly A. Muellers, Li Chen, Rachel O’Conor, or Alex D. Federman. Dr Michael S. Wolf has unrestricted research grants from Merck, Sharpe, Dohme and Eli Lily; has consulted for Luto UK and Pfizer and received honoraria from MedLearning Group, NYU. Dr Wisnivesky has received consulting honorarium from Quintiles, AstraZenaca, Sanofi and Merck, and research grants from Sanofi and Quorum.
| Abbreviations | ||
| HL | = | Health literacy |
| COPD | = | Chronic obstructive pulmonary disease |
| LABA | = | Long-acting bronchodilator |
| ICS | = | Inhaled corticosteroid |
| SMB | = | Self-management behavior |
| S-TOFHLA | = | Short Test of Functional Health Literacy in Adults |
| MARS | = | Medication Adherence Rating Scale |
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References
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