Depression is an established risk factor for the development of coronary heart disease (CHD) in healthy patients and for adverse cardiovascular outcomes in patients with existing CHD. Dietary factors resulting in lower levels of omega-3 fatty acids not only increase CHD risk, but may also be involved in the pathophysiology of depression.
The investigators measured red blood cell levels of two omega-3 fatty acids, docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA), and assessed depressive symptoms in a cross-sectional study of 987 adults with CHD. Omega -3 fatty acids were blindly measured in fasting venous blood samples using capillary gas chromatography to measure the fatty acid composition of red blood cell membranes. Red blood cell levels of EPA and DHA are presented as a percentage composition of total fatty acid methyl esters. The investigators assessed current depression using the 9-item Patient Health Questionnaire. They evaluated the association between omega -3 fatty acid levels and depressive symptoms as continuous variables using linear regression.