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PURPOSE: In this cross-sectional survey, we assessed the prevalence of dry eye disease (DED) in a representative German population sample. In addition, we examined the associations between DED, health-related quality of life (HRQoL), and level of fatigue. Finally, we further validated the German version of the Standard Patient Evaluation of Eye Dryness (SPEED) questionnaire and present norm data of the German population. METHODS: A random sample of German residents aged 16 years and older was recruited between October and December 2021. All participants completed the SPEED, Short Form 36, and Multidimensional Fatigue Inventory 20 questionnaires. RESULTS: Of the 2495 participants who completed the survey, 450 (21.6%; 95% confidence intervals 20.0-23.1) reported a SPEED total score of ≥4, indicating a positive screening for DED. DED was significantly more common in women and older age. Participants who screened positive for DED reported significantly higher levels of fatigue and lower values in all domains of HRQoL. A receiver operating characteristic curve of the SPEED was generated using an ophthalmologist's diagnosis. The area under the curve was estimated to be 0.886 (95% confidence intervals 0.858-0.913). A cutoff score ≥4 seemed to be appropriate as an indicator of DED. Cronbach's α was excellent (0.95). CONCLUSIONS: DED is common in the German population. We confirmed associations with sex, age, HRQoL, and fatigue level, indicating a high burden of DED. The German version of the SPEED is a valid instrument for the assessment of DED symptoms.
RESUMEN
Objective: The Multidimensional Fatigue Inventory (MFI-20) is commonly used, but its factor structure remains unclear. The MFI-20 consists of five subscales (general fatigue, physical fatigue, reduced activity, reduced motivation, and mental fatigue). This study investigates the psychometric properties, including the factor structure, of a general German population sample and tests group hypotheses on gender and age. Another objective is to provide normative data by gender and age groups. Methods: Using data from a representative German sample (n=2,509), reliability and convergent validity measures, group hypothesis testing, and confirmatory/exploratory factor analyses were conducted. Results: The MFI-20 demonstrated satisfactory internal consistency and showed adequate convergent validity with the SF-36. All subscales of the MFI-20 were significantly correlated (0.71-0.85). Physical fatigue exhibited the highest (0.42) and mental fatigue had the lowest (0.19) correlation with age. Fatigue scores were significantly higher for women and significantly increased with age. A five-factor structure showed poor model fit; using an exploratory factor analysis, a two-factor structure emerged (a general factor and a mental/motivational factor). Conclusion: The MFI-20 is a reliable and valid instrument for measuring fatigue in the general population, but the five-factor structure is not supported. The subscale general fatigue or the MFI-20 total score might measure fatigue sufficiently. The provided norms can be used for further research and individual assessment.