An analysis of trials published in six leading general medical journals in 1999 shows that only 14 of 90 trials (16%) that looked at at least one of the top 10 causes of the global burden of disease were highly relevant to international health, as assessed by World Health Organization criteria (CMAJ 2004; 170:1673-7). Seven of the 35 most deadly and debilitating diseases were not studied in any published trial.

The journals in the analysis were Annals of Internal Medicine, BMJ, JAMA (the journal of the American Medical Association), Lancet, New England Journal of Medicine, and CMAJ (the journal of the Canadian Medical Association).

Of the 286 randomised controlled trials published, 124 (43%) addressed one of 35 major diseases. Of these diseases ischemic heart disease, HIV and AIDS, and cerebrovascular disease were the most commonly studied. Ninety trials (32%) covered one of the top 10 leading causes of disease in the world.

Twelve experts from international health organisations rated the studies for relevance to international health. The mean rating was 2.6 (standard deviation 1.5) out of 5.0. Only 14 (16%) of the 90 trials were rated as 4.0 or more, indicating high relevance to international health. Almost half of the 40 leading causes of the global burden of disease were not studied in any trial.

The authors note that more than two thirds of the world’s population live in low income countries, where health priorities differ from more affluent parts of the world. The most impoverished 20% of the world’s people are nine times more likely to die of infectious disease and 10 times more likely to die in childhood than people living in rich nations.

The Global Forum for Health Research estimates that less than 10% of spending on health research is directed toward diseases or conditions that account for 90% of the global burden of disease, a phenomenon referred to as the “10/90 gap.”

Lack of relevant research, difficulties with the publication process, such as an inability to write in English, editorial bias in favour of the interests of Western culture, and restricted access to scientific information may all be to blame, researchers in developing countries have said.

In an accompanying commentary Dr Prabhat Jha, director of Toronto’s St Michael’s Hospital Centre for Global Health Research, and colleagues say that much more research should be done into the few major diseases that account for the gap between rich and poor countries so that mortality and morbidity among the world’s poor people can be reduced (CMAJ 2004;170:1687-8).

© 2004 BMJ Publishing Group Ltd