Pilot test
The pilot test responses did not identify the need for any further changes to the content of the questionnaire.
Study participants and sociodemographic characteristics
A total of 517 responses were collected (517/2,500; 21% response rate), thus meeting the required sample size. The median age of respondents was 55 years, and 58.2% were female (Table 1). Most of the respondents had secondary education (47.0%) and monthly income less than 700€ (27.5%). Respondents rated their general self-perceived health assessment as good (33.5%), followed by very good (25.7%), acceptable (23.2%), excellent (12.0%), and poor (4.3%).
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Reliability
The results of the reliability tests of the 1-, 3-, 4-, and 12-factor models are shown in Table 2. With two exceptions, all results had acceptable reliability, meaning that the Cronbach’s alpha was above 0.700. The highest Cronbach’s alpha was obtained for the 1-factor model, followed by the 3-, 4-, and 12-factor models. In the 12-factor model, two factors had particularly low Cronbach’s alpha values and include items 21 and 29. Indices in the 12-factor model that included item 21 were Disease prevention and Understand information, with items 21 (…understand health warnings about behaviour such as smoking, low physical activity and drinking too much?), 22 (…understand why you need vaccinations?), and 23 (…understand why you need health screenings?). Item 21 referred to understanding indicators of an unhealthy lifestyle, while the other two items referred to understanding preventive measures (i.e., vaccinations and screenings). The indices in the 12-factor model that included item 29 were Disease prevention and Apply information, with items 29 (…decide if you should have a flu vaccination?), 30 (…decide how you can protect yourself from illness based on advice from family and friends?), and 31 (…decide how you can protect yourself from illness based on advice from media?). Item 29 specifically referred to deciding about vaccination, while the other two referred to deciding about general protection against diseases. Omitting items 21 and 29 resulted in higher reliability for the 12-factor model (Cronbach’s alpha above 0.700); however, omitting these items from the 1-, 3-, and 4-factor models decreased the reliability of these models.
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Validity
CFA
The CFA showed that the 12-factor model provided the highest validity and the 1-factor model provided the lowest with respect to all three indices studied, namely chi-square value, RMSEA, and CFI (Table 3). A closer look at the standardized regression weights for the 12-factor model revealed that item 29 had a low factor loading (<0.50; Appendix 5). Since omitting items 21 and 29 resulted in higher reliability of the 12-factor model, the validity of the 12-factor model without these two items was examined and found to be higher than that of the original 12-factor model (χ2 value/df 3.242; CFI 0.829; RMSEA 0.066, CI 0.063 to 0.069; p < 0.001). The 3-factor model had higher validity than the 4-factor model, suggesting that respondents were better able to differentiate between the three main health contexts than the four health information processing competencies. All models showed reasonable model fit, but none of them fully satisfied the marginal values of all indices. The path diagrams of all factor models from IBM SPSS AMOS are shown in Appendix 1, 2, 3, and 4.
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Univariate analysis
Univariate analysis results are reported in Table 4. These results showed that older people were less educated, had lower income, and lower general self-perceived health assessment. Health literacy index decreased with age, and it increased with higher general self-perceived health assessment. Other factors were not significantly correlated with health literacy index.
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Multiple linear regression
Regarding health literacy index, participants were classified as ‘inadequate’ (45/517; 8.7%), ‘problematic’ (234/517; 45.3%), ‘sufficient’ (184/517; 35.6%), and ‘excellent’ (54/517; 10.4%). All variance inflation factors were below 2 and the tolerance statistics were all above 0.2, indicating minor multicollinearity among the factors. Only general self-perceived health assessment and age had high proportions on the same small eigenvalue, indicating that the variances of their regression coefficients were dependent. The dependent variable, health literacy index, was positively correlated with general self-perceived health assessment; when the latter increased by one unit on a scale of 1 to 5, the health literacy index increased by 1.910 (p < 0.001, Table 5). Lower health literacy index was observed in almost all regions outside the Osrednjeslovenska region, but the result was not statistically significant in most cases. Other independent variables such as gender, age, education attained, and monthly income were not significantly associated with the health literacy index.
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