Evidence for non-communicable diseases: analysis of Cochrane reviews and randomised trials by World Bank classification

INTRODUCTION

Prevalence of non-communicable diseases (NCDs) is increasing globally, with the greatest projected increases in low-income and middle-income countries. We sought to quantify the proportion of Cochrane evidence relating to NCDs derived from such countries.

METHODS

We searched the Cochrane database of systematic reviews for reviews relating to NCDs highlighted in the WHO NCD action plan (cardiovascular, cancers, diabetes and chronic respiratory diseases). We excluded reviews at the protocol stage and those that were repeated or had been withdrawn. For each review, two independent researchers extracted data relating to the country of the corresponding author and the number of trials and participants from countries, using the World Bank classification of gross national income per capita.

RESULTS

797 reviews were analysed, with a reported total number of 12 340 trials and 10 937 306 participants. Of the corresponding authors 90% were from high-income countries (41% from the UK). Of the 746 reviews in which at least one trial had met the inclusion criteria, only 55% provided a summary of the country of included trials. Analysis of the 633 reviews in which country of trials could be established revealed that almost 90% of trials and over 80% of participants were from high-income countries. 438 (5%) trials including 1 145 013 (11.7%) participants were undertaken in low-middle income countries. We found that only 13 (0.15%) trials with 982 (0.01%) participants were undertaken in low-income countries. Other than the five Cochrane NCD corresponding authors from South Africa, only one other corresponding author was from Africa (Gambia).

DISCUSSION

The overwhelming body of evidence for NCDs pertains to high-income countries, with only a small number of review authors based in low-income settings. As a consequence, there is an urgent need for research infrastructure and funding for the undertaking of high-quality trials in this area.

In vitro comparison of two NONOates (novel nitric oxide donors) on rat pulmonary arteries

The pulmonary vasorelaxant properties of two NONOates (diazeniumdiolates) were examined because this novel group of nitric oxide (NO) donors may be useful in pulmonary hypertension. MAHMA NONOate ((Z)-1-¿N-Methyl-N-[6-(N-methylammoniohexyl)amino]¿ diazen-1-ium-1,2-diolate) and spermine NONOate ((Z)- 1-¿N-[3-aminopropyl]-N-[4-(3-aminopropylammonio)butyl]-amino¿di azen-1-ium-1,2-diolate) decomposed at different rates (half-lives 1.3 min and 73 min, respectively; 37 degrees C, pH 7.3) but generated the same total amount of NO. They fully relaxed submaximally contracted ring preparations of main and intralobar pulmonary arteries from rats. Responses were inhibited by the guanylate cyclase inhibitor, ODQ (1H-[1,2,4]Oxadiazolo[4,3-a]quinoxalin-1-one). Potency was not affected by choice of contractile spasmogen (phenylephrine, endothelin-1, thromboxane-mimetic) or endothelium removal, and tolerance did not develop; thus the drugs had properties important for use in pulmonary hypertension. MAHMA NONOate was 10-40-fold more potent than spermine NONOate but responses to spermine NONOate were more sustained (spermine NONOate > 60 min; MAHMA NONOate < 7 min). It is concluded that the differences in potency and time-course reflect the different rates of NO generation by these NONOates.