Only one in ten are studying prevention while almost two thirds focus on drug therapy

An analysis of diabetes trials worldwide has found they are not addressing key issues relating to the condition with almost two thirds focusing on drug therapy while only one in ten addresses prevention or behavioural therapies. The research is published in Diabetologia, the journal of the European Association for the Study of Diabetes (EASD), and is by Dr Jennifer Green, Duke University Medical Center, Durham, NC, USA, and colleagues.

There are an estimated 371 million people with diabetes in the world. By 2030, there will be some 550 million with diabetes based on current trends. As such, research addressing the whole spectrum of diabetes care and treatment is essential. To examine whether current studies adequately address these needs, Green and colleagues analysed diabetes-related trials registered with from 2007--2010.

The researchers found 2,484 interventional trials by selecting those with disease condition terms relevant to diabetes. Of these, 75% had a primarily therapeutic purpose while just 10% were preventive. Listed interventions were mostly drugs (63%) while few were behavioural (12%). Most of the studies were also small to medium sized, and were designed to enrol 500 or fewer participants (91%) or 100 or fewer (59%) participants, with mean/median times to completion of 1.8/1.4 years.

A very small proportion of trials targeted persons aged 18 years and under (4%). This may be appropriate given the number of children currently affected by diabetes; however, the estimated 3% annual increase in incidence of type 1 diabetes may warrant greater representation. Furthermore, the increase in type 2 diabetes among adolescents, particularly noticeable in wealthier nations, is of considerable concern, since as Dr Green notes "it is unclear whether findings obtained from trials of adults with diabetes are readily translatable to paediatric/adolescent populations".

And despite the fact that nearly 20% of adults worldwide aged 65 years and over have diabetes, less than 1% of trials specifically targeted this age group, while 31% actually excluded patients over 65 years and almost all excluded those over 75 years.

"Only a tiny proportion of the trials analysed--1.4%--listed primary outcomes including mortality or clinically significant cardiovascular complications," says Dr Green. "Furthermore, distribution of registered trials by country does not reliably correlate with diabetes prevalence."

The International Diabetes Federation list of the 10 locations most affected by diabetes includes six Middle Eastern countries in which diabetes prevalence among adults is approximately 20% (Kuwait, Lebanon, Qatar, Saudi Arabia, Bahrain and the United Arab Emirates). However, this analysis by Green and colleagues, suggests that this region is minimally involved in the registered diabetes-related trials. Comparison of trial activities in countries with the highest diabetes prevalence among adults revealed 1126 trials in the USA. China, India and Mexico participated in 101--250 trials each; however, the Russian Federation (12.6 million persons with diabetes) and Brazil (12.4 million) are involved in fewer than 100 registered trials despite these heavy disease burdens.

Dr Green also says: "Rates of complications including diabetic retinopathy, lower extremity amputation, and end-stage renal disease vary among ethnic groups. To achieve the greatest impact upon clinical care, trials should enrol patients representative of populations disproportionately affected by diabetes and its complications. A better understanding of responses to interventions among diverse individuals and groups may inform individualised treatments of greater effectiveness and tolerability."

She concludes: "The majority of diabetes-related trials include small numbers of participants, exclude those at extremes of age, are of short duration, involve drug therapy rather than preventive or non-drug interventions, and do not focus upon significant cardiovascular outcomes. Recently registered diabetes trials may not sufficiently address important diabetes care issues or involve affected populations...Although many trials will provide valuable information upon completion, our review suggests that the current portfolio does not adequately address disease prevention, management, or therapeutic safety. This information may be meaningful in the allocation of future research activities and resources."