The Impact of Health Literacy on Adherence to Factor Replacement in the Hemophilia Population

Background:

Health literacy (HL) is the degree to which individuals have the capacity to obtain, process, and understand basic health information and services needed to make appropriate health decisions. Numeracy, a component of HL, is defined as the ability to handle numerical concepts. Both low HL and low numeracy have been associated with poor adherence to treatment regimens in a variety of chronic diseases.

For the management of hemophilia, a chronic bleeding disorder, adherence to treatment regimens can be difficult and requires completion of multiple complex tasks. We hypothesized that lower HL and lower numeracy are associated with decreased adherence to treatment in persons with hemophilia (PWH). A secondary aim of this study was to evaluate other demographic and clinical characteristics that may be associated with adherence.

Methods:

In a cross-sectional study, adult PWH completed questionnaires to assess the main outcome variable, adherence measured by the validated hemophilia regimen treatment adherence scale (VERITAS) and the primary independent variables, HL as measured by the shortened Test of Functional Health Literacy in Adults (sTOFHLA) and numeracy as measured by the Schwartz-Woloshin questions. Other potential independent or confounding variables including general demographic and clinical information, the General Self-Efficacy (GSE) Scale, the Wake Forest Physician Trust Scale (WFPTS), and the Haem-A-QoL were also collected. Analysis proceeded from descriptive statistics to bivariable associations using simple linear regression and multivariable analysis using multiple linear regression.

Results:

All were men (n=99); 91% had hemophilia A and 78% had severe disease. Mean age was 34 years (standard deviation (SD) 11.5). White race was reported by 69% and 6% were Hispanic. Income was reported to be ≥$50,000 in 39%; and 37% had received an undergraduate degree or higher. Mean length of time seen at the Hemophilia Treatment Center (HTC) was 16.0 years (SD 11). HIV infection was noted in 26%, and 59% were HCV positive; depression history was reported in 21%; 49% infused replacement factor prophylactically. Most of the study population (95%) had high HL; but only 23% were numerate. The mean VERITAS-Pro was 45.6 (SD 12.7) and mean VERITAS-PRN was 51.0 (SD 11.2) with a lower score indicating greater adherence.

On bivariable analysis, adherence was significantly associated with depression history, GSE score, WFPTS score, and Haem-A-QoL score (p < 0.05). On multivariable analysis, HL score and numerate status were not significantly associated with adherence (see Table). Being on any chronic medication, longer time seen at HTC, higher physician trust, and better quality of life were significantly associated with higher adherence. Depression history was significantly associated with lower adherence. This model overall accounted for a moderate proportion of the variability of adherence between subjects (adjusted R² = 0.296).

Conclusion:

In this study population, HL and numeracy were not associated with adherence. A large majority of the PWH in our study were health literate; however, the study population was limited to those who made it to their scheduled HTC appointments and were sufficiently on time to allow completion of study questionnaires which may have biased this study toward a more literate population. This study population did show that being on any chronic medication, longer time seen at the HTC, higher physician trust, and better quality of life were significantly associated with better adherence. Depression history was significantly associated with lower adherence. These factors provide a better understanding of characteristics that influence adherence and may prove important for optimizing the care of PWH.