 Analyses: All parameters of oxidative stress before and during treatment with both statins will be compared to determine whether atorvastatin causes a stronger and quicker reduction of oxidative stress than simvastatin. Generalized estimating equations GEE will be used to compare these effects. We plan to include a minimum of 30 patients in each treatment-group from the outpatient clinic of the department of internal medicine of the VU University Medical Center in Amsterdam. 