Nancy D Berkman

Non-randomised studies of the effects of interventions are critical to many areas of healthcare evaluation, but their results may be biased. It is therefore important to understand and appraise their strengths and weaknesses. We developed ROBINS-I (“Risk Of Bias In Non-randomised Studies - of Interventions”), a new tool for evaluating risk of bias in estimates of the comparative effectiveness (harm or benefit) of interventions from studies that did not use randomisation to allocate units (individuals or clusters of individuals) to comparison groups. The tool will be particularly useful to those undertaking systematic reviews that include non-randomised studies.

BACKGROUND: Approximately 80 million Americans have limited health literacy, which puts them at greater risk for poorer access to care and poorer health outcomes. PURPOSE: To update a 2004 systematic review and determine whether low health literacy is related to poorer use of health care, outcomes, costs, and disparities in health outcomes among persons of all ages. DATA SOURCES: English-language articles identified through MEDLINE, CINAHL, PsycINFO, ERIC, and Cochrane Library databases and hand-searching (search dates for articles on health literacy, 2003 to 22 February 2011; for articles on numeracy, 1966 to 22 February 2011). STUDY SELECTION: Two reviewers independently selected studies that compared outcomes by differences in directly measured health literacy or numeracy levels. DATA EXTRACTION: One reviewer abstracted article information into evidence tables; a second reviewer checked information for accuracy. Two reviewers independently rated study quality by using predefined criteria, and the investigative team jointly graded the overall strength of evidence. DATA SYNTHESIS: 96 relevant good- or fair-quality studies in 111 articles were identified: 98 articles on health literacy, 22 on numeracy, and 9 on both. Low health literacy was consistently associated with more hospitalizations; greater use of emergency care; lower receipt of mammography screening and influenza vaccine; poorer ability to demonstrate taking medications appropriately; poorer ability to interpret labels and health messages; and, among elderly persons, poorer overall health status and higher mortality rates. Poor health literacy partially explains racial disparities in some outcomes. Reviewers could not reach firm conclusions about the relationship between numeracy and health outcomes because of few studies or inconsistent results among studies. LIMITATIONS: Searches were limited to articles published in English. No Medical Subject Heading terms exist for identifying relevant studies. No evidence concerning oral health literacy (speaking and listening skills) and outcomes was found. CONCLUSION: Low health literacy is associated with poorer health outcomes and poorer use of health care services. PRIMARY FUNDING SOURCE: Agency for Healthcare Research and Quality.

The concept of health literacy evolved from a history of defining, redefining, and quantifying the functional literacy needs of the adult population. Along with these changes has come the recognition that sophisticated literacy skills are increasingly needed to function in society and that low literacy may have an effect on health and health care. We present a brief history of literacy in the United States, followed by a discussion of the origins and conceptualization of health literacy. Increased attention to this important issue suggests the need to review existing definitions of the term "health literacy," because despite the growing interest in this field, one question that persists is, "What is health literacy?"

OBJECTIVES: To update a 2004 systematic review of health care service use and health outcomes related to differences in health literacy level and interventions designed to improve these outcomes for individuals with low health literacy. Disparities in health outcomes and effectiveness of interventions among different sociodemographic groups were also examined. DATA SOURCES: We searched MEDLINE®, the Cumulative Index to Nursing and Allied Health Literature, the Cochrane Library, PsychINFO, and the Educational Resources Information Center. For health literacy, we searched using a variety of terms, limited to English and studies published from 2003 to May 25, 2010. For numeracy, we searched from 1966 to May 25, 2010. REVIEW METHODS: We used standard Evidence-based Practice Center methods of dual review of abstracts, full-text articles, abstractions, quality ratings, and strength of evidence grading. We resolved disagreements by consensus. We evaluated whether newer literature was available for answering key questions, so we broadened our definition of health literacy to include numeracy and oral (spoken) health literacy. We excluded intervention studies that did not measure health literacy directly and updated our approach to evaluate individual study risk of bias and to grade strength of evidence. RESULTS: We included good- and fair-quality studies: 81 studies addressing health outcomes (reported in 95 articles including 86 measuring health literacy and 16 measuring numeracy, of which 7 measure both) and 42 studies (reported in 45 articles) addressing interventions. Differences in health literacy level were consistently associated with increased hospitalizations, greater emergency care use, lower use of mammography, lower receipt of influenza vaccine, poorer ability to demonstrate taking medications appropriately, poorer ability to interpret labels and health messages, and, among seniors, poorer overall health status and higher mortality. Health literacy level potentially mediates disparities between blacks and whites. The strength of evidence of numeracy studies was insufficient to low, limiting conclusions about the influence of numeracy on health care service use or health outcomes. Two studies suggested numeracy may mediate the effect of disparities on health outcomes. We found no evidence concerning oral health literacy and outcomes. Among intervention studies (27 randomized controlled trials [RCTs], 2 cluster RCTs, and 13 quasi-experimental designs), the strength of evidence for specific design features was low or insufficient. However, several specific features seemed to improve comprehension in one or a few studies. The strength of evidence was moderate for the effect of mixed interventions on health care service use; the effect of intensive self-management inventions on behavior; and the effect of disease-management interventions on disease prevalence/severity. The effects of other mixed interventions on other health outcomes, including knowledge, self-efficacy, adherence, and quality of life, and costs were mixed; thus, the strength of evidence was insufficient. CONCLUSIONS: The field of health literacy has advanced since the 2004 report. Future research priorities include justifying appropriate cutoffs for health literacy levels prior to conducting studies; developing tools that measure additional related skills, particularly oral (spoken) health literacy; and examining mediators and moderators of the effect of health literacy. Priorities in advancing the design features of interventions include testing novel approaches to increase motivation, techniques for delivering information orally or numerically, "work around" interventions such as patient advocates; determining the effective components of already-tested interventions; determining the cost-effectiveness of programs; and determining the effect of policy and practice interventions.