Response to Letter Regarding Article “Effect Size Estimates of Lifestyle and Dietary Changes on All-Cause Mortality in Coronary Artery Disease Patients: A Systematic Review”
The letter by Colquhoun et al points to the fact that during the publication of our review,1 simultaneous reports of an international research fraud investigation appeared, raising suspicion of the work of R.B. Singh. In our review, we used 3 publications by this author, which describe the dietary effects on mortality in coronary artery disease patients: 1 study on body weight management2 and 2 on combined dietary interventions.3,4
The letter of Colquhoun et al reinforces the view already expressed in our review. Studies on body weight management in coronary artery disease patients are insufficient to provide a reliable estimate of the mortality effect. The study by Singh on this issue2 was already considered a low-quality study and not used in an effect estimate.
We also agree with Colquhoun et al that, as a result of the suspected research fraud, the available data on combined dietary interventions are even more “meager” than previously thought. The remaining randomized controlled trial and cohort study alone are insufficient to provide a reliable effect estimate.
The analyses of the following lifestyle factors are unaffected by this problem: smoking cessation, physical activity, and moderate alcohol consumption. For dietary interventions, the situation remains that no reliable effect estimate can be provided for any of the 6 investigated dietary goals, individually or in combination. We, therefore, wholeheartedly endorse the view of Colquhoun et al that there is an urgent need for more evidence from randomized controlled trials in this field and that these trials should be monitored to high-quality standards.
Iestra JA, Kromhout D, van der Schouw YT, Grobbee DE, Boshuizen HC, van Staveren WA. Effect size estimates of lifestyle and dietary changes on all-cause mortality in coronary artery disease patients: a systematic review. Circulation. 2005; 112: 924–934.
Singh RB, Rastogi SS, Verma R, Laxmi B, Singh R, Ghosh S, Niaz MA. Randomised controlled trial of cardioprotective diet in patients with recent acute myocardial infarction: results of one year follow up. BMJ. 1992; 304: 1015–1019.
Singh RB, Dubnov G, Niaz MA, Ghosh S, Singh R, Rastogi SS, Manor O, Pella D, Berry EM. Effect of an Indo-Mediterranean diet on progression of coronary artery disease in high risk patients (Indo-Mediterranean Diet Heart Study): a randomised single-blind trial. Lancet. 2002; 360: 1455–1461.