Aim: The overall aim was to measure health literacy (HL) in people with type 2 diabetes (T2DM) and in the general Norwegian population.

Methods: Sampling 388 people with T2DM (papers I, II and IV) and 900 individuals (III) in the general Norwegian population a cross-sectional design was applied. Rasch modelling and confirmatory factor analysis were used to evaluate the psychometric properties of the 47 items HLS-EU-Q47 questionnaire (I and III) and the 14 items FCCHL scale (II), and to develop and evaluate a 12 item short version, HLS-N-Q12 (III and IV), based on HLS-EU-Q47. Descriptive and inferential statistics were used to describe HL and to investigate associations between HL and various independent variables.

Main results: The HLS-EU-Q47 displayed psychometric shortcomings in both populations (I and III). A 12-dimensional model described the data best. Several items showed misfit to the Rasch model and statistical dependence. Aiming at meeting the requirements of objective measurement, the HLS-N-Q12 was suggested (III and IV). Evaluating the FCCHL in people with T2DM, the data fitted a three-dimensional model best (II). Several items showed misfit to the Rasch model and unordered response categories. However, a three-dimensional 12-item version of the FCCHL had acceptable psychometric properties. Education, good general health and empowerment were positively associated with HL in people with T2DM, explaining about 17% of the total variance in HL (IV).

Conclusions: In both populations, the HLS-N-Q12 displayed solid psychometric properties and might therefore be used as a measure of HL for both clinical and research purposes. Nurses and other health professionals must be aware that HL influence individuals’ proficiency in managing their health. Hence, nurses and other health professionals should map HL in individuals and adapt health information accordingly.

Hensikt: Avhandlingens overordnede hensikt var å måle health literacy (HL) blant personer med diabetes type 2 (T2DM) og generell norsk befolkning.

Metode: Kvantitativ tverrsnittsstudie hvor 388 personer med T2DM (I, II og IV) og 900 personer fra norsk befolkning (III) var inkludert. Rasch modellering og konfirmatorisk faktoranalyse ble anvendt for å evaluere de psykometriske egenskapene til instrumentene HLS-EU-Q47 (I og III) og FCCHL (II), som består av henholdsvis 47 og 14 spørsmål, og for å utvikle og evaluere en kortversjon av HLS-EU-Q47, HLS-N-Q12, bestående av 12 spørsmål (III og IV). Deskriptiv og inferensiell statistikk ble anvendt for å beskrive HL i utvalgene og for å studere sammenhenger mellom HL og ulike uavhengige variabler.

Hovedresultater: HLS-EU-Q47 viste psykometriske svakheter i begge utvalgene (I og III). HLS-EU-Q47 data viste best tilpasning til en 12-dimensjonal modell. Flere spørsmål viste dårlig tilpasning til Rasch modellen, samt statistisk avhengighet. Med hensikt i å oppnå kravene for objektive målinger, ble HLS-N-Q12 foreslått (III og IV). I evalueringen av FCCHL blant personer med T2DM viste data best tilpasning til en tredimensjonal modell (II). Spørsmål med dårlig tilpasning til Rasch modellen og uordnede svarkategorier ble avdekket. Imidlertid viste en tredimensjonal versjon av FCCHL bestående av 12 spørsmål akseptable psykometriske egenskaper. Utdanning, god generell helse og empowerment, var positivt assosiert med HL blant personer med T2DM, og forklarte rundt 17% av den totale variansen av HL (IV).

Konklusjoner: HLS-N-Q12 viste solide psykometriske egenskaper i begge populasjonene og kan derfor anvendes for å måle HL både i praksis og innen forskning.  Sykepleiere må være oppmerksomme på at HL påvirker den enkeltes muligheter for å håndtere egen helse. Sykepleiere bør dermed kartlegge HL hos den enkelte og tilpasse helseinformasjon deretter.

In today’s health care, we are accountable for our own health and responsible for making cautious health-related decisions based on available information. Health literacy is a vital competence in accomplishing this. Knowledge about people’s health literacy is therefore central to nurses aiming at adapting health information to target groups. The overall aim of this thesis was to measure health literacy in people with type 2 diabetes and in the general Norwegian population.

This thesis demonstrates the usefulness of Rasch modelling as an addition to confirmatory factor analysis in evaluating psychometric properties of health-related scales, such as the HLS-EU-Q47 and the FCCHL. The results indicate that the short form of HLS-EU-Q47, the HLS-N-Q12, meet the assumptions and the requirements of fundamental measurements and could be used to measure health literacy in both people with type 2 diabetes and in the general Norwegian population.

Judging whether health information from various sources are valid and reliable was found to be the most difficult health-literacy task in both populations. Explaining variance in health literacy in people with type 2 diabetes, health literacy stood out as being positively associated with education, good general health and empowerment.