Part 1 | Vascular risk factors for depression and apathy 33 2 such self-reported information to be moderately accurate (concordance with GP: κ = 0.56; 95% confidence interval [CI], 0.48-0.64) 20. Therefore, we considered a stroke to have occurred if the self-reported and GP information were consistent or if a cardiac specialist confirmed the GP diagnosis of stroke. Death due to stroke was established based on death certificates registered by the Netherlands Central Bureau of Statistics. Death certificates of deceased participants were 100% complete. Stroke was defined as ICD-9 codes 431, 433, 434, and 436 and ICD-10 codes I-61, I-63, and I-64. The event was timed as occurring in the year halfway between the 3-yearly assessments for nonfatal strokes and as the year of death for fatal strokes. Depression Depressive symptoms were measured using the Center for Epidemiological Studies– Depression Scale (CES-D). This is a widely used instrument to measure depressive symptoms in the community 21. In LASA, the traditional cutoff of the CES-D of 16 or greater had a sensitivity of 100% and a specificity of 88% for MDD 22. Major depressive disorder was diagnosed using the National Institute of Mental Health Diagnostic Interview Schedule (DIS) 23. Subthreshold depressive disorder (SDD) was diagnosed if a study participant scored 16 or higher on the CES-D but did not meet DSM-III diagnostic criteria for MDD on the DIS. The SDD category included 107 respondents with a CES-D score of 16 or higher but no available DIS diagnosis. We use the term CRDSs were refer to the broad category of MDD or SDD, and we use the term depressive symptoms to refer to the score on the CES-D (range, 0-60). The DIS and CES-D were completed every 3 years, which made it possible to estimate the mean severity of depressive symptoms and the chronicity of CRDSs and MDD during the follow-up. The mean severity of depressive symptoms was defined as the mean CES-D score of all observations until the year of the first stroke or censoring divided by the total number of observations in this interval. The chronicity of MDD was defined as the total number of observations of MDD until the year of the first stroke (or censoring) divided by the total number of observations in this interval. The chronicity of CRDSs was the total number of observations of an MDD or a score on the CES-D of 16 or higher until the year of the first stroke (or censoring) divided by the total number of observations in this interval. Cardiac Disease Cardiac disease was defined as myocardial infarction, congestive heart failure, angina pectoris, or cardiac arrhythmia and established at baseline using an algorithm used earlier in LASA6. This algorithm uses 3 sources of information: self-reported, medication, and GP information. We considered only 1 confirmative source necessary for diagnosis because self-reported cardiac disease is sufficiently accurate in LASA (concordance with GP: κ = 0.69; 95% CI, 0.65-0.73) 20. We used a broad definition of cardiac disease because although it could lead to a type II error (overcorrection), the use of a more restricted definition could lead to a type I error (undercorrection), and we preferred to use the broader category.
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