Allan, CL; (2014) Brain MRI correlates of depression and vascular risk: Whitehall Imaging sub-study. Doctoral thesis , UCL (University College London).

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Abstract

This thesis combines neuroimaging and epidemiological techniques to investigate the hypothesis that late-life depressive symptoms are partially caused by vascular risk factors. Magnetic resonance imaging (MRI) was used to study the structural brain changes associated with depressive symptoms, major depressive disorder and long-term exposure to vascular risk factors (hypertension, dyslipidaemia, diabetes, smoking and Framingham stroke risk). This was complemented by an epidemiological approach to investigate whether vascular risk factors are associated with depressive symptoms. A sample of participants from the Whitehall II study were invited to take part in the Whitehall Imaging sub-study at the University of Oxford. Participants recruited between April 2012 and June 2013 (n=229, mean age 69, age range 60-82 years, 83% male) underwent detailed cognitive testing, a clinical interview and a multi-modal 3 Tesla MRI brain scan. Depressive symptoms were measured at previous Whitehall II phases, and again in 2012-2013 using a structured assessment for DSM-IV mood disorder and a self-report questionnaire. Long-term exposure to vascular risk factors was measured at five collection phases between 1985 and 2009. Ten percent of participants (n=23) had current depressive symptoms and 13% (n=29) had late-onset depressive symptoms (depression onset after age 60). Current and late-onset depressive symptoms were associated with reduced white matter integrity in frontal-subcortical areas. Study of the MRI correlates of vascular risk factors also showed an association between long-term exposure to high fasting glucose (mean across five examinations between 1985 and 2009) and reduced white matter integrity in frontal-subcortical areas. However, long-term exposure to other vascular risk factors was not significantly associated with depressive symptoms. In conclusion, while vascular risk factors were not consistently related to late-life depressive symptoms, long-term exposure to high glucose levels and depressive symptoms were both associated with reduced white matter integrity in frontal-subcortical areas.

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