Since the International Committee of Medical Journal Editors began requiring clinical trials to be registered in a public trial registry at their outset as a condition of publication, ClinicalTrials.gov has become a useful repository of interesting data, Nature Reviews notes. And so a report examined all “industry-sponsored” Phase II through Phase IV studies on November 1, 2007, including trials that were first registered between October 2005 and September 2007.

And what do we learn? Most registered trials were in oncology, followed by central nervous system disorders, cardiology, infectious diseases, endocrinology, and respiratory diseases. These six therapeutic areas accounted for 68 percent of 3,515l protocols and 74 percent of 94,135 sites. The number of registered trials for each area corresponds to the leading causes of deaths reported for developed countries, the mag points out.

Among the six largest therapeutic areas, respiratory diseases, endocrinology and oncology showed a growth in the number of trials in the period analyzed. The highest relative growth was seen for rheumatology - 157 percent - and the lowest was for cardiology, 74.3 percent. The number of studies increased for three of the top ten diseases: rheumatoid arthritis, asthma and hepatitis. In fact, rheumatoid arthritis became the third most common disease for clinical trials.

A considerable change in the focus of trials in therapeutic areas is, therefore, noticeable over just two consecutive years, the mag concludes. Not surprisingly, oncology is the largest therapeutic area in terms of clinical-trial activity, while there was a decline in cardiology. Here is a useful chart and a useful table.