BACKGROUND: The factors influencing medication adherence have not been fully elucidated. Inadequate health literacy skills may impair comprehension of medical care instructions, and thereby reduce medication adherence.
OBJECTIVES: To examine the relationship between health literacy and medication refill adherence among Medicare managed care enrollees with cardiovascular-related conditions.
RESEARCH DESIGN: Prospective cohort study.
SUBJECTS: New Medicare enrollees from 4 managed care plans who completed an in-person survey and were identified through administrative data as having coronary heart disease, hypertension, diabetes mellitus, and/or hyperlipidemia (n=1,549).
MEASURES: Health literacy was determined using the short form of the Test of Functional Health Literacy in Adults (S-TOFHLA). Prospective administrative data were used to calculate the cumulative medication gap (CMG), a valid measure of medication refill adherence, over a 1-year period. Low adherence was defined as CMG ≥ 20%.
RESULTS: Overall, 40% of the enrollees had low refill adherence. Bivariate analyses indicated that health literacy, race/ethnicity, education, and regimen complexity were each related to medication refill adherence (P<.05). In unadjusted analysis, those with inadequate health literacy skills had increased odds (odds ratio [OR]=1.37, 95% confidence interval [CI]: 1.08 to 1.74) of low refill adherence compared with those with adequate health literacy skills. However, the OR for inadequate health literacy and low refill adherence was not statistically significant in multivariate analyses (OR=1.23, 95% CI: 0.92 to 1.64).
CONCLUSIONS: The present study suggests, but did not conclusively demonstrate, that low health literacy predicts poor refill adherence. Given the prevalence of both conditions, future research should continue to examine this important potential association.
Haynes RB, Yao X, Degani A, Kripalani S, Garg A, McDonald HP. Interventions to enhance medication adherence. Cochrane Database of Systematic Reviews, 2005.Google Scholar
Sabate E. Adherence to long-term therapies: Evidence for action. Geneva: World Health Organization, 2003. Available at: http://www.who.int/chronic_conditions/adherencereport/en/. Accessed July 2005.Google Scholar
The Boston Consulting Group. The hidden epidemic: finding a cure for unfilled prescriptions and missed doses; 2003. Available at: http://www.bcg.com/media_center/media_press_releases.jsp?id=1057. Accessed April 2006.Google Scholar
McDermott MM, Schmitt B, Wallner E. Impact of medication nonadherence on coronary disease outcomes: a critical review. Arch Intern Med. 1997;157:1921–9.PubMedCrossRefGoogle Scholar
Chobanian AV, Bakris GL, Black HR, et al. The Seventh Report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure. JAMA. 2003;289:2560–72.PubMedCrossRefGoogle Scholar
The Coronary Drug Project Research Group. Influence of adherence to treatment and response of cholesterol on mortality in the coronary drug project. N Engl J Med. 1980;303:1038–41.CrossRefGoogle Scholar
Stewart RB, Caranasos GJ. Medication compliance in the elderly. Med Clin of North Am. 1989;73:1551–63.Google Scholar
Col N, Fanale Je, Kronholm P. The role of medication noncompliance and adverse drug reactions in hospitalizations of the elderly. Arch Intern Med. 1990;150:841–5.PubMedCrossRefGoogle Scholar
Murray MD, Callahan CM. Improving medication use for older adults: an integrated research agenda. Ann Intern Med. 2003;139(part 2):425–9.PubMedGoogle Scholar
MacLaughlin EJ, Raehl CL, Treadway AK, Sterling TL, Zoller DP, Bond CA. Assessing medication adherence in the elderly. Which tools to use in clinical practice? Drugs Aging. 2005;22:231–55.PubMedCrossRefGoogle Scholar
Census PHC-T-9 Population by AGe, Sex, Race and Hispanic or Latino Origin for the United States: 2000. Available at: http://www.census.gov/population/cen2000/phc-t9/tab01.pdf. Accessed December 2005.Google Scholar
Lamy PP. Prescribing for the Elderly. Littleton: PSG Publishing; 1980.Google Scholar
Morrow D, Leirer V, Sheikh J. Adherence and medication instructions: review and recommendations. J Am Geriatr Soc. 1988;36:1147–60.PubMedGoogle Scholar
Gray SL, Mahoney JE, Blough DK. Medication adherence in elderly patients receiving home health services following hospital discharge. Ann Pharmacother. 2001;35:539–45.PubMedCrossRefGoogle Scholar
Esposito L. The effects of medication education on adherence to medication regimens in an elderly population. J Adv Nurs. 1995;21:935–43.PubMedCrossRefGoogle Scholar
Hanchak NA, Patel MB, Berlin JA, Strom BL. Patient misunderstanding of dosing instructions. J Gen Intern Med. 1996;11:325–8.PubMedCrossRefGoogle Scholar
Morrell RW, Park DC, Poon LW. Quality of instructions on prescriptions drug labels: effects on memory and comprehension in young and old adults. Gerontologist. 1989;29:345–54.PubMedGoogle Scholar
Chung MK, Bartfield JM. Knowledge of prescription medications among elderly emergency department patients. Ann Emerg Med. 2002;39:605–8.PubMedCrossRefGoogle Scholar
Persell SD, Heiman HL, Weingart SN, et al. Understanding of drug indications by ambulatory care patients. Am J Health Syst Pharm. 2004;61:2523–7.PubMedGoogle Scholar
Rosenow EC III. Patients’ understanding of and compliance with medications: the sixth vital sign? Mayo Clin Proc. 2005;80:983–7.PubMedCrossRefGoogle Scholar
Raynor DK, Silletto M. Patient noncomprehension of labeled instructions. Pharm J. 1982;229:648–9.Google Scholar
Kalichman SC, Ramachandran B, Catz S. Adherence to combination antiretroviral therapies in HIV patients of low health literacy. J Gen Intern Med. 1999;14:267–73.PubMedCrossRefGoogle Scholar
Institute of Medicine. Health Literacy: A Prescription to End Confusion. Washington, DC: National Academy Press; 2004.Google Scholar
Ratzan S, Parker R. Introduction. Current bibliographies in Medicine 2000–1: Health literacy January 1990 through October 1999. Bethesda, MD: National Library of Medicine (February 2000). Available at: http://www.nlm.nih.gov/pubs/cbm/hliteracy.html.Google Scholar
Davis T, Crouch M, Wills G, Miller S, Adebhou D. The gap between patient reading comprehension and the readability of patient education materials. J Fam Pract. 1990;31:533–8.PubMedGoogle Scholar
Weiss BD. Health Literacy: A Manual for Clinicians. AMA Foundation; 2003.Google Scholar
Green J, Hibbard J. How much do health literacy and patient activation contribute to older adults’ ability to manage their health? Available at: http://www.aarp.org/research/health/healthliteracy/2005_05_literacy.html. Accessed December 2005.Google Scholar
Pignone M, DeWalt DA, Sheridan S, Berkman N, Lohr KN. Interventions to improve health outcomes for patients with low literacy. A systematic review. J Gen Intern Med. 2005;20:185–92.PubMedCrossRefGoogle Scholar
Golin CE, Liu H, Hays RD, et al. A prospective study of predictors of adherence to combination antiretroviral medications. J Gen Intern Med. 2002;17:756–65.PubMedCrossRefGoogle Scholar
Chew LD, Bradley KA, Flum DR, Cornia PB, Koepsell TD. The impact of low health literacy on surgical practice. Am J Surg. 2004;188:250–3.PubMedCrossRefGoogle Scholar
Gazmararian JA, Baker DW, Williams MV, et al. Health literacy among Medicare enrollees in a managed care organization. JAMA. 1999;281:545–51.PubMedCrossRefGoogle Scholar
Ware JE, Kosinski M, Keller SD. SF-36 Physical and Mental Health Summary Scales: A User’s Manual. Boston, MA: The Health Institute; 1994.Google Scholar
Yesavage JA, Brink TL, Rose TL. Development and validation of a geriatric depression screening scale: a preliminary report. J Psychiatr Res. 1999;17:37–49.CrossRefGoogle Scholar
Folstein MF, Folstein SE, McHugh PR. “Mini-mental state”. A practical method for grading the cognitive state of patients for the clinician. J Psychiatr Res. 1975;12:189–98.PubMedCrossRefGoogle Scholar
Remington PL, Smith MY, Williamson DF, Anda RF, Gentry EM, Hogelin GC. Design, characteristics, and usefulness of state-based behavioral risk factor surveillance: 1981–87. Pub Health Rep. 1988;103:366–75.Google Scholar
Baker DW, Williams MW, Parker RM, Gazmararian JA. Development of a brief test to measure functional health literacy. Patient Educ Couns. 1999;38:33–42.PubMedCrossRefGoogle Scholar
Steiner JF, Prochazka AV. The assessment of refill compliance using pharmacy records: methods, validity, and applications. J Clin Epidemiol. 1997;50:105–16.PubMedCrossRefGoogle Scholar
Parker RM, Baker DW, Williams MV, Nurss JR. The test of functional health literacy in adults: a new instrument for measuring patients’ literacy skills. J Gen Intern Med. 1995;10:537–41.PubMedCrossRefGoogle Scholar
National Council for Prescription Drug Program, Basic Guide to Standards. February 2006.Google Scholar
Vermeire E, Hearnshaw H, Van Royen P, Denekens J. Patient adherence to treatment: three decades of research. A comprehensive review. J Clin Pharm Ther. 2003;26:331–42.CrossRefGoogle Scholar
Haynes RB, Taylor DW, Sackett DL, eds. Compliance in Health Care. Baltimore: Johns Hopkins; 1979.Google Scholar
Grant RW, O’Leary KM, Weilburg JB, Singer DE, Meigs JB. Impact of concurrent medication use on statin adherence and refill persistence. Arch Intern Med. 2004;164:2343–8.PubMedCrossRefGoogle Scholar
Shalansky SJ, Levy AR. Effect of number of medications on cardiovascular therapy adherence. Ann Pharmacother. 2002;36:1532–9.PubMedCrossRefGoogle Scholar
Kaplan RC, Bhalodkar NC, Brown EJ, White J, Brown DL. Race, ethnicity, and sociocultural characteristics predict noncompliance with lipid-lowering medications. Prev Med. 2004;39:1249–55.PubMedCrossRefGoogle Scholar
Schectman JM, Bovbjerg VE, Voss JD. Predictors of medication-refill adherence in an indigent rural population. Med Care. 2002;40:1294–300.PubMedCrossRefGoogle Scholar
Weng FL, Israni AK, Joffe MM, et al. Race and electronically measured adherence to immunosuppressive medications after deceased donor renal transplantation. J Am Soc Nephrol. 2005;16:1839–48.PubMedCrossRefGoogle Scholar
Raji MA, Kuo YF, Salazar JA, Satish S, Goodwin JS. Ethnic differences in antihypertensive medication use in the elderly. Ann Pharmacother. 2004;38:209–14.PubMedGoogle Scholar
Li X, Margolick JB, Conover CS, et al. Interruption and discontinuation of highly active antiretroviral therapy in the multicenter AIDS cohort study. JIDS. 2005;38:320–8.Google Scholar
Dominick KL, Golightly YM, Bosworth HB. Racial differences in analgesic/anti-inflammatory medication adherence among patients with osteoarthritis. Ethnic Disease. 2005;15:116–22.Google Scholar
Klein D, Turvey C, Wallace R. Elders who delay medication because of cost: health insurance, demographic, health, and financial correlates. Gerontologist. 2004;44:779–87.PubMedGoogle Scholar
Haynes RB, McKibbon KA, Kanani R. Systematic review of randomized trials of interventions to assist patients to follow prescriptions for medications. Lancet. 1996;348:383–6.PubMedCrossRefGoogle Scholar