Part II | Vascular risk factors for depression and apathy 85 5 Measures Primary outcome measure- apathy The presence and severity of apathy at the 6-year follow-up was assessed by means of the self-report version of the 14-item Starkstein apathy scale (SAS) 29. This scale is wellvalidated and a score of ≥14 is considered to indicate severe apathy 30. Depressive symptom severity was assessed with the Inventory of Depressive Symptomatology-Self Report (IDS-SR), a well-validated depressive symptom questionnaire 31 32. Since the sum score of the SAS and IDS strongly correlated (r=0.47, p<.001), we decided to conduct sensitivity analyses based on the apathy and mood dimensions revealed by a principal component analysis (PCA) on all items of the SAS and the IDS using their original four-point Likert scale. We applied an oblimin rotation with Kaiser normalization and replaced missing item-data by means. Identified apathy and mood factors were computed by using the Anderson-Rubin method and used as dependent variables in the regression analyses. We checked for robustness by performing principal component analyses on the SAS and IDS with dichotomized answers, as well as by performing the PCA for both scales separately. These additional sensitivity analyses did not change the factor solution presented in the Supplemental Information. As shown in the supplemental material, we identified two apathy factors, i.e., amotivation and loss of initiative, and one mood factor. Items that loaded (>0.4) on the amotivation factor were “Are you interested in new things?”, “Does anything interest you?”, “Do you put much effort into things?”, “Are you always looking for something to do?”, “Do you have plans and goals for the future?”, and: “Do you have motivation?”. Items that loaded (>0.4) on the initiative factor were “Does someone has to tell you what to do each day?”, “Are you indifferent to things?”, “Are you unconcerned with many things?”, “Do you need a push to get started on things?”, “Are you neither happy nor sad, just in between?”, and:” Would you consider yourself apathetic?”. Items that loaded (>0.4) on the mood factor were “Feeling sad”, “Feeling irritable”, “Feeling anxious or tense”, “Response of your mood to good or desired events”, “The quality of your mood”, “Concentration/decision Making”, “View of myself”, “View of my future”, “Thoughts of death or suicide”, “General interest”. Both apathy factors were used as primary outcome variables in the analyses, whereas the mood factor was included as a covariate to adjust for confounding.
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