a1 Department of Research and Development (RaD), Levanger Hospital, Health Trust Nord-Trøndelag, Norway
a2 Department of Neuroscience, Unit for Psychiatry and Behavioural Science, Faculty of Medicine, Norwegian University of Science and Technology, Trondheim, Norway
a3 Swedish National Institute of Public Health, Östersund, Sweden
a4 Department of Social Medicine, University of Bristol, UK
a5 Department of Public Health and General Practise, Norwegian University of Science and Technology, Trondheim, Norway
Background Elevated levels of circulating C-reactive protein (CRP) have been associated with coronary heart disease and, in some studies, depression. Most studies have been of populations selected by age and/or gender. We investigate these associations with depression, myocardial infarction (MI), or both, in a large general population sample.
Method A cross-sectional population study of 9258 women and men aged ≥20 years. The study included clinical examination, self-report of MI and depression and factors known to confound their associations. The Hospital Anxiety and Depression Scale was used to assess severity of depressive symptoms. Elevated high sensitive-CRP was defined as values >2.2 mg/l.
Results The association of elevated CRP with depression was attenuated towards the null [from odds ratio (OR) 1.28, p=0.001 to OR 1.08, p=0.388] following extensive adjustment, while associations with MI (adjusted OR 1.42, p=0.032) and co-morbid MI and depression (adjusted OR 2.66, p=0.003) persisted. Confounders associated with elevated CRP levels were smoking (OR 1.66; p<0.001), chronic physical illness (OR 1.34, p<0.001), BMI ≥30 (OR 1.13, p<0.001), employment (OR 0.70, p<0.001) and high coffee consumption (OR 0.83, p=0.017). Interaction tests indicated a lower effect of old age (OR 0.54, p<0.001) and smoking (OR 0.63, p<0.001) on elevated CRP levels in women compared with men.
Conclusions CRP levels were raised in those with MI and co-morbid MI and depression; the positive association with depression was explained by confounding factors. We found new evidence that might help understand gender-specific patterns. Future studies should explore the neurobiological mechanisms underpinning these interrelations and their relevance for treatment of these conditions.
(Received March 19 2008)
(Revised March 25 2010)
(Accepted March 30 2010)
(Online publication May 06 2010)