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.
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.
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.
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.