Confounding and indication for treatment in evaluation of drug treatment for hypertension

Non-randomised comparisonsConfounding by indication commonly creates unsurmountable problems for non-randomised research on treatment effects.Valid inferences can be drawn only under those rare circumstances in which (a) groups of patients with the same indications but different Can blood pressure be lowered too far?The debate continues MARCUS ROSE Summary pointsConfounding by indications for treatment is a serious threat to the validity of non-randomised comparisons of treatment effects Conclusions about the efficacy of treatment should not be drawn from comparisons of treated and untreated patients Under some circumstances, confounding by indication in a non-randomised study can be limited or even removed in the design phase or data analysis Reported increased risks of heart disease in hypertensive patients with low blood pressure during treatment may be attributable to pre-existing severe atherosclerosis rather than "overtreatment"Unequivocal rejection of all non-randomised studies assessing treatment effects is unjustified