Impact of Inadequate Health Literacy
The negative effects of low health literacy can be found on many levels when a patient attempts to access and utilize the health-care system. Literacy deficits can inhibit a patient’s ability to attend appointments, follow prescription directions, and make informed decisions about their treatment plan. The largest study of health literacy conducted to date in the United States found that 30% of patients at two public hospitals could not read or comprehend basic health-related materials. In addition, 42% failed to understand directions for taking medications, 60% could not comprehend a routine consent form, and 26% did not understand the information written on an appointment slip.
Patients with inadequate health literacy have difficulty controlling chronic illness and are more likely to be hospitalized, resulting in an additional $69 billion in health-care costs annually.[1,18] These patients are also less likely to participate in disease prevention programs. Female patients with poor literacy skills have been found to have difficulty understanding commonly recommended cancer screening tests such as Pap smears and mammograms.[19,20] The effect of heath literacy on patient morbidity and mortality, especially in the elderly, has become clearer over the past decade. A 1997 prospective cohort study of 3,260 Medicare managed-care enrollees in four US metropolitan areas found that inadequate health literacy, as measured by reading fluency, independently predicted all-cause mortality and cardiovascular death among community-dwelling elderly persons.
Inadequate Health Literacy and Cancer Patients
It is common for oncologists and other health-care providers to use information about rates, percentages, and proportions when discussing treatment and prognosis. An important component of health literacy in the context of cancer treatment is the patient’s ability to understand these basic probability and numeric concepts. Health numeracy can be defined as the degree to which individuals have the capacity to access, process, interpret, communicate, and act on numeric, quantitative, graphic, biostatistical, and probabilistic health information needed to make effective health decisions. Recent studies have found inadequate numeracy skills in the general patient population, and especially in older adults.
Although there is a correlation between prose or print literacy and numeracy, many patients have adequate literacy but poor quantitative skills. A cross-sectional study of 200 primary care patients tested numeracy and comprehension of basic food labels. While 75% of patients reported at least a high school education and 77% had 9th grade literacy skills, only 37% had 9th grade math skills. Only 37% of patients could calculate the number of carbohydrates consumed from a 20-oz bottle of soda that contained 2.5 servings.
Decreased numeracy competency in cancer patients may have an impact on their ability to accurately assess their own health risks. Studies have shown that cancer patients regularly overestimate their survival rates. For instance, the Study to Understand Prognoses and Preferences for Outcomes and Risks of Treatments (SUPPORT)—a prospective cohort study of outcomes and decision-making in hospitalized patients with serious illnesses including late stage colon and lung cancer—found that 82% of patients’ survival estimates were more optimistic than physician’s estimates.[24,25] These differences in survival estimates may be correlated with lower health numeracy given that numeracy has been shown to already affect patient comprehension of colorectal cancer risk. In a study of 254 women aged 40 to 85 years, researchers analyzed lifetime and 5-year breast cancer risk perceptions and found subjects had a mean estimation error for lifetime and 5-year risk of 29.5% and 24.8%, respectively.  These estimation errors were significantly correlated with lower numeracy rates.
The prevalence of deficient numeracy may have a significant impact on quality-of-life instruments that are often used in medical oncology to analyze alternative treatments that have equivalent survival rates. A study of newly diagnosed head and neck cancer patients showed that 50% had poor numeracy ability. Furthermore, the patient’s lack of facility with numeric expressions impaired their ability to provide meaningful data on quality-of-life assessment performed with utility instruments.
Inadequate Health Literacy and Older Cancer Patients
More than 60% of new cancers and 70% of cancer deaths occur in people over the age of 65 years. Older adults diagnosed with cancer are especially vulnerable to the effects of poor health literacy and are at the greatest risk for poor communication with health professionals. Rapidly expanding treatment options and overall complexity of cancer management require higher involvement of patients in decision-making.
A limited number of studies have focused on the prevalence and impact of health literacy in geriatric cancer patients. A survey of Medicare enrollees between June and December 2007 demonstrated that 34% of English-speaking and 50% of Spanish-speaking respondents had inadequate or marginal health literacy. Reading ability declined dramatically with age, even after adjusting for years of school and cognitive impairment. One study in newly diagnosed prostate cancer patients with a mean age of 67 demonstrated that low health literacy limited patient understanding of complex information regarding treatment and quality-of-life issues.
Physician-patient communication is a process by which information is exchanged between a physician and patient through a common system of symbols, signs, and behaviors. Communication is a core clinical skill in the practice of medical oncology, and health literacy has a central role in cancer patients’ ability to discuss their disease and prognosis with their oncologist in a meaningful way. The average clinical career of an oncologist is approximately 40 years and can involve up to 200,000 consultations with patients and their families. As with the general population, effective communication has many positive effects on cancer patients’ adjustment to the disease and its treatment, whereas poor communication has negative consequences for both health-care professionals and patients.[32,33]