Development and validation of a diabetes/nutrition knowledge questionnaire in type 1 and type 2 diabetes

Aims: Effective diabetes management requires adherence to medication regimens and nutritional guidelines, underscoring the importance of health literacy. Our study aimed to develop and validate diabetes and nutrition knowledge questionnaires and correlate diabetes-specific health literacy with glucose metrics in people with type 1 and type 2 diabetes. Methods: In a cross-sectional study at a Swiss tertiary centre, questionnaires were developed to assess diabetes and nutrition knowledge in 289 participants with type 1 diabetes on insulin pumps or basal-bolus insulin and 222 participants with type 2 diabetes with or without insulin. Questionnaire validation involved content and construct validity established by a multidisciplinary team, and measurement properties were evaluated using the Rasch model. Multiple linear regression was performed to analyse the relationship between scores and glucose metrics. Results: The questionnaire demonstrated strong content and construct validity, with minor item misfits identified. In type 1 diabetes participants, higher nutrition knowledge scores (>= 9/10) were significantly associated with reduced HbA1c levels (-5 mmol/mol or -0.47%, p < 0.05) and increased TIR (+9.2%, p < 0.05). No significant associations were observed in type 2 diabetes after adjusting for confounders, such as gender, BMI and diabetes duration. Conclusions: We developed and validated a questionnaire encompassing diabetes and nutrition knowledge, tailored to diabetes type and treatment strategy. Psychometric analysis demonstrated robust measurement properties for assessing health literacy across diverse diabetes populations. Better nutrition knowledge was significantly linked to improved glycaemic control in type 1 diabetes, reflected by lower HbA1c and increased TIR.