<qa>  What is the main cause of comorbidity among breast cancer patients?Comorbidity among breast cancer patients has been thoroughly studied over the past years. Previous research has however, primarily focused on prevalence of comorbidity at the time of the cancer diagnosis manifest comorbidity and less attention has been paid to studying latent comorbidity developing after the diagnosis, which can be a result of the treatment. Furthermore it is not known if the incidence of this later developed comorbidity is different in breast cancer patients compared to the general population. Additionally, most studies do not address specific diseases but focus on comorbidity as such. Emerging evidence, however, indicates that cardiovascular disease CVD encompassing cerebrovascular disease manifested by stroke and TCI and coronary heart disease manifested by infarction, arrhythmias, heart failure and sudden death and diabetes may play a pivotal role, because it contributes importantly both to total mortality and to breast cancer specific mortality among breast cancer survivors. 