Our analysis shows that inadequate literacy skills are significantly associated with reduced MMC, and in particular, an inability to identify medications. Depending on the modeling strategy, patients with inadequate literacy had 10 to 18 times the odds of being unable to identify all of their medications, compared with those with adequate literacy skills. Individuals with marginal literacy skills also appeared less able to identify medications, although this effect was not statistically significant.
Summary scores on the DRUGS were similar to those seen in other reports.8,9
Unfortunately, the 2 published manuscripts and several abstracts reporting DRUGS performance did not describe relative ability on each of the component tasks,8,9,12–15,21–25
so we are unable to compare our findings on the identification domain with other studies. Nevertheless, given the present results, it is possible that a reasonable estimate of MMC could be obtained only by asking patients to identify their medications. This would be a welcome methodological refinement as the full DRUGS test takes 5 to 15 minutes to administer. Such an approach is most likely to be useful when the patients lack physical limitations (and can therefore open pill bottles without difficulty), and when they are primarily prescribed medications to be taken as 1 pill per day, as was the case in the present investigation. Under these circumstances, scores on the opening, dosing, and timing components of the DRUGS are likely to be high and demonstrate little variability, as was observed here.
Some clinicians may presume that patients who identify their medications on the basis of the pills' color and shape are more likely to have inadequate literacy skills. Our results do not support this relationship. When presented with their own medication bottles, patients with inadequate literacy skills were no more likely to look at the pills in order to identify the medications. Future research should seek to validate this observation, perhaps framing the identification task in a different manner.
Our findings may shed some light on the larger issue of medication adherence. Despite decades of research on medication use, the reasons behind nonadherence remain unclear.2–4
Recent evidence points to poor literacy as a risk factor, likely through its effect on patients' ability to understand how to follow the medication regimen. Kalichman et al.26
demonstrated that patients with lower literacy skills were less adherent to antiretroviral therapy, and this effect persisted after controlling for other variables. Low-literacy patients in that study often cited confusion about the regimen as a reason for nonadherence.26
Other studies have shown that low-literacy patients struggle to understand medication instructions. In a survey of Medicare managed care enrollees, Gazmararian et al.27
found that 47.5% of adults with inadequate literacy skills incorrectly described the timing of medication doses when looking at a pill bottle, compared with 24.4% of those with marginal, and 11.5% of those with adequate literacy skills. Similarly, 54.3% of respondents with inadequate literacy skills could not describe how to take medication on an empty stomach, compared with 33.7% and 15.6% of those with marginal and adequate literacy skills, respectively.27
These published findings, combined with results of the present investigation, suggest that inadequate literacy skills significantly impact patients' ability to manage medications. Because understanding how to take medications could be considered a prerequisite for taking them correctly, we expect literacy to be connected to adherence and even with rates of medication errors, but the current evidence is limited. Additional research is needed to investigate the relationship between literacy and medication use, with attention to mediating and moderating factors.
There are several limitations to this study. First, it was conducted in a single institution, which serves a predominately low-literacy, African-American population with a large burden of chronic disease. However, this high-risk group warrants study, as it is more likely to benefit from future interventions to improve medication self-management and adherence. Further, our results were consistent with several preliminary reports of literacy and MMC in different settings.12–15
Second, the DRUGS measure could only be performed among patients who brought their medications to the clinic. While there were no important clinical differences between patients who brought and did not bring their medicines, it is possible that unmeasured factors (e.g., number of medications, actual understanding of the medication regimen, or adherence rates) were different among the subjects in this analysis who brought their medications to their clinic visit when prompted to do so by a phone call versus those who did not adhere to such instruction.
Third, scores on the DRUGS were high overall and distributed nonparametrically. Although similar score distributions have been observed in prior research and we applied appropriate statistical techniques, the clinical relevance of deficits in MMC is uncertain. DRUGS scores have been associated with some clinical outcomes, such as functional decline and emergency department use, but the instrument is relatively new, and further investigation is required to establish its predictive value.8
In summary, we found a large independent association between literacy and MMC, primarily in patients' ability to identify their medications. The present investigation adds to the growing body of evidence, suggesting that inadequate literacy skills may be an important risk factor for poor comprehension and medication mismanagement. Physicians and pharmacists should strive to educate low-literacy patients more fully about proper medication use. Additional research is also needed into strategies that may facilitate such education, such as improved packaging, labeling, and dispensing practices.