Population aging is a global reality.1 As there is an increase in individuals aged 60 years and older, there is also a rise in the prevalence of diseases, especially chronic noncommunicable diseases, such as hypertension, cancer, dementia, and others.1,2 These diseases require adequate care and often require continuous medication and routine medical examinations and consultations. However, negligence on the part of the patient (i.e., older adult), poor lifestyle habits (e.g., unhealthy diet, physical inactivity, and others)3,4 and failure to attend routine medical checkups5 can lead to health complications. A contributing factor to these adverse results is low health literacy, which is recognized as a social determinant of health.6

Health literacy is characterized as the individual's ability to access, understand, interpret, and apply information and guidelines for prescriptions, consultations, and other health-related services in different formats (e.g., written, spoken or digital).7, 8, 9 It is related to personal knowledge and skills that are acquired over a lifetime through daily experiences and social interactions.2 Limited health literacy in older adults has emerged as a significant public health problem.10 It can lead to erroneous intake of prescribed medications or non-adherence to medication, restricted access to health services for routine exams and consultations, and inadequate management of noncommunicable diseases;5 in addition, it may increase the risk of mortality.11

Systematic reviews relating aging and health literacy have concluded that advanced age is strongly associated with poor health literacy.10,12,13 Older adults aged 65 and above in North America, for example, require skills related to health literacy to interact effectively with the health care system.14 Furthermore, another review identified that poor health literacy is associated with worse health outcomes in this population.15 However, it is noteworthy that these aforementioned reviews do not include any articles published after 2016. Other recent reviews have been published, but with specific groups that include older adults (e.g., people with noncommunicable diseases, people with type 2 diabetes mellitus).16,17 Recent systematic reviews of health literacy among older adults are unknown.

Although there are different reviews of the literature that have evaluated the health literacy in older adults, there is a need for a broader search. These reviews have specific inclusion criteria, such as: conducted exclusively in the United States12,15 or in South Asia;17 carried out with older adults over 65 years old and using different methods;13 studies using specific measures to assess health literacy10 and; including only articles published in English.10,13,16 These specificities highlight the gap in a more comprehensive understanding of health literacy in different contexts, including participants from developing countries.

Health literacy plays a key role for older adults and can protect their health, minimizing complications. Understanding the factors that are associated with poor health literacy in older adults can enable the development of strategies to ensure their quality of life and minimize negative impacts on health. In addition, it can support the development of public policies targeted at this demographic. Thus, this systematic review has the main objective of identifying the factors associated with poor health literacy in older adults.