Observational studies versus RCTs: what about socioeconomic factors?

摘要

Jan Vandenbroucke (April 11, p 1233)1 explores possible explanations for the conflicting messages between observational studies and randomised controlled trials on the effects of hormone replacement therapy (HRT) on coronary heart disease (CHD). We claim that socioeconomic factors are an even more important explanation. Women who receive HRT are generally healthier and better educated than those who are not. Similarly, drugs for erectile dysfunction (sildenafil) in Sweden are dispensed more frequently to well educated than to low-educated people,2 and well educated men in Sweden also have better access to planned coronary revascularisation than other men with the same need. Lawlor and colleagues showed that the reduction in relative risks for CHD seen in observational studies (but not randomised trials) disappeared when socioeconomic status was controlled for.