One in five long-term BCSs had HL levels in the marginal or inadequate range. HL at this level likely limits the ability to understand and make use of health related information and engage in effective self-management, which are key aspects of successful cancer survivorship.
Three HL-items were labelled as easy or very easy by 90% or more of the sample, reflecting a high degree of more basic or functional HL skills, such as following written instructions. However, 35-41% reported difficulty with advanced HL tasks, such as complex judgment calls regarding treatment and health risks, which reflect the cognitive domain “appraisal” in the original HL framework . These findings support the theory that HL is as a multi-dimensional concept which may vary across health-related contexts. This is in line with other studies, including the European Health Literacy survey (HLS-EU), where items reflecting more advanced, critical HL skills were experienced as the most difficult [6, 33]. In the HLS-EU, HL was as expected highest in Western European countries, but with substantial variations related to age, health and socioeconomic status . BC risk is positively associated with high socioeconomic status, and the majority of BCSs in this survey had high SES. This may account for the relatively high mean HL score. The most critical HL skills for cancer survivorship may still be lacking for a substantial proportion of survivors. In line with previous findings, we observed an association between lower HL and increasing age [12, 16]. Old age involves declining sensory and cognitive functioning which may affect HL skills directly. Additionally, with age the risk of comorbidity also increases. Multi-morbid, more fragile patients report lower HL when faced with cancer than patients with higher performance status , possibly because they already engage in complex self-management behaviors. Dealing with cancer in this context may exceed their overall coping capacity. BCSs of older age may therefore represent a particularly vulnerable group with regards to the effects of low HL.
FCR, the persistent fear or worry that the cancer will return or progress , is a frequent concern among BCSs , shown to persist over time, also among survivors with favorable long-term prognosis, such as BC . In the present study, FCR was the only late effect that remained significantly associated with HL in the adjusted model. Our finding is in line with results presented by Halbach et al who concluded that limited HL is an independent risk factor for higher levels of FCR . Low HL may impact the risk of FCR through different mechanisms, such as reduced ability to navigate, critically assess, understand and handle health related information, but also through sub-optimal interaction with health care providers, for instance through avoidance behavior. Among cancer patients, low HL has been associated with lower perceived information provision and information satisfaction compared to higher HL . Combined, low HL may result in unmet informational and supportive care needs and perhaps unnecessarily high levels of FCR, as demonstrated in previous studies .
In an oncological setting, neuroticism, the propensity for negative emotions when faced with negative stress, has been associated with reduced quality of life and increased risk of post-traumatic stress disorder following cancer . Neuroticism may affect self-management behaviors, as reported for patients with other chronic diseases such as diabetes , thereby linking it to HL-skills. Although research is limited, low HL has been associated with neuroticism . We observed the same association, which remained stable in the adjusted analyses. We have not been able to find other studies specifically exploring HL and neuroticism among BCSs warranting further investigations. Our finding implies that specific personality characteristics may indicate poorer HL-skills. Such knowledge may be valuable in a clinical setting making it easier for clinicians to identify individuals at risk of poorer outcomes.
As symptom burden and functional limitations increase, self-perceived HL and self-management seem to decline . Following this line of reasoning, individuals with low HL may be particularly vulnerable when faced with treatment related late effects. This was not the case in the present sample. This may be due to the survivors’ relatively high HL levels, enabling them to handle these stressors, or that increasing demands in fact has stimulated HL skills over time. It is also possible that HL is more clearly linked to late effects during the first years of cancer survivorship, before effective coping strategies are in place and the emotional distress is likely to be higher. Exploring HL among BC patients living with advanced disease will be interesting for further studies.
Strengths and limitations
BCSs in this study were recruited from an unselected, unbiased population. All long-term, early-stage BCSs diagnosed with BC within working age registered in the CRN were invited to participate, granting us with a large sample of high quality.
Given the inclusion criteria for the present study, non-responders did not differ according to diagnosis (early-stage BC), gender or time of diagnosis. Additional clinical data from the CRN concerning cancer-related variables revealed only slight differences between responders and non-responders. We cannot exclude the possibility that non-responders differ according to other variables, such as ethnic background and HL skills, as reading and understanding Norwegian was necessary in order to complete the questionnaire. However, data use restrictions prohibited us from performing complete analyses of the non-responders. Although declining response rates in health surveys in general may threaten external validity, a response rate of 49% is considered acceptable and comparable to other large-scale surveys on long-term cancer survivors in Norway . Furthermore, in comparable survey-studies, with more modest response rates than reported here, evidence of response bias was not found .
This sample reflects the Norwegian BCS population, which is quite homogenous in terms of SES and ethnic background. Although the results are likely to be generalizable to a Scandinavian and Western-European setting, more caution must be pain when interpreting the results within a more global context. We only included survivors of working age at diagnosis (20-65 years) given the main outcomes of interest in the SWEET study. Inclusion of the oldest age groups may have further underlined the importance of increasing age as a risk factor for poor HL, and should be further explored in upcoming studies.
Causal inference is not possible given the cross sectional design of this study. Data on HL is based on self-report, and reflect present skills. Although validated in the Norwegian population and for Norwegians with diabetes type II [20, 43], the HLS-Q12 it has not been extensively used. Furthermore, categorization of HL is empirically based, and threshold values will vary. Consequently we chose to use HL as a continuous variable for the regression analyses. The HLS-Q47 allows for the opportunity to measure HL across three health care settings. This procedure has not been described for the HLS-Q12 as of yet. Still, the HLS-Q12 is reported to be a valid, quick and easy-to-use tool to measure HL in a clinical setting.