Specific Health Knowledge and Health Literacy of Patients before and after Bariatric Surgery: A Cross-Sectional Study

Background: It is an important condition for adequate weight loss and prevention of adverse events that bariatric surgery (BS) candidates possess good specific health knowledge. There is a paucity of standardized instruments to evaluate the specific health knowledge of patients before and after BS. Therefore, we developed a 32-item multiple-choice test covering the main aspects of life which are important after BS, and investigated the correlation of specific health knowledge with health literacy, level of depression and anxiety, percentage of excess weight loss, and specific complications of BS in postoperative patients. Methods: Two groups participated in the cross-sectional study: the preoperative group (n = 109) was recruited from candidates for BS (gastric bypass or sleeve gastrectomy), the postoperative group (n = 110) was recruited from patients 12–74 months after BS (average 33 months, SD = 16.5). Both groups had completed a preoperative multimodal training program. Specific health knowledge was assessed with a newly developed knowledge questionnaire. Health literacy was evaluated with the short version of the European Health Literacy Survey (HLS-EU-Q16). The 9-item Patient Health Questionnaire (PHQ-9) and the 7-item Generalized Anxiety Scale (GAD-7) were used to assess the levels of depression and anxiety. Results: The pre- and postoperative group did not differ with regard to the number of correctly answered questions on the knowledge questionnaire, with 75% correct answers in both groups (p = 0.059). No correlations were found with health literacy (p = 0.498) and levels of depression (preoperative group: p = 0.279; postoperative group: p = 0.242) and anxiety (preoperative group: p = 0.866; postoperative group: p = 0.119). In postoperative patients specific health knowledge was not associated with the weight loss achieved (p = 0.437). Conclusion: The newly designed knowledge questionnaire can be useful for screening specific knowledge of BS patients at different time points.