Part 1 | Vascular risk factors for depression and apathy 63 4 Introduction Late-life depression is a frequent and serious health problem, with reported prevalence rates of 1.8% for major and 10.2% for minor depression 1. Depressed elderly patients are less healthy, they have more functional limitations, use health services more often and experience a lower quality of life than their non-depressed counterparts 2. This makes knowledge about determinants of late-life depression highly relevant for patients, physicians and policy makers. Since the prevalence of depression is higher in elderly with vascular disease, it has been hypothesized that cerebrovascular disease (CVD) plays a causative role in the incidence and persistence of depressive symptoms among older adults 3. White matter hyperintensities (WMH) on MRI scans of the brain may reflect ischemia due to CVD 4. The onset and outcome of depression have been associated with the volume of WMH 5 6. Clinically, CVD can be evident or ‘silent’. Associations between cerebrovascular risk factors (CVRF) and depression have been found 7 8 9 10 11. CVRF can predict the volume of WMH 12 13 14 and as such can be used as a proxy for ‘silent’ CVD in epidemiological research. The vascular depression hypothesis has stimulated research into biological predictors of depression, thereby often paying less attention to other theories of depression. Research of the role of personality in the onset of depression has shown that neuroticism is an important vulnerability factor for depression. Neuroticism is a stable trait that can be measured reliably, even in later life; it is not significantly affected by physical health 15. Throughout life, a neurotic personality raises the odds with at least 49 % of developing depressive symptoms and major depression 16. This effect of neuroticism is independent of age and has also been established in older people 17. Since higher levels of neuroticism and CVRF/CVD often co-occur in patients with latelife depression, not only the impact of each of these vulnerability factors but also their interactions need to be studied. A positive interaction between CVRF/CVD and neuroticism would be likely since neuroticism raises the depressogenic effects of life-events 18 and physical illness 19; and because neuroticism has a negative influence on adherence to medical treatment in cardiac and other patients 20 21. So far the interaction between CVRF/ CVD and neuroticism in models of late-life depression has only been studied in a small case-control design with negative results 22. The objective of the present study was to investigate the interplay of vascular disease and neuroticism in explaining depression in later life in a large population sample. As both the prevalence of depression 23 and of its vulnerability factors-vascular disease and neuroticism- differ by gender 24 25 particular attention will be paid to sex-specific effects.
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