Prevalence of randomised controlled trials in Japanese cardiovascular journals: a descriptive study

Little is known about the recent proportion and trends of randomised controlled trials (RCTs) published in Japanese cardiovascular journals.

This study retrospectively reviewed all original research articles published between 2006 and 2015 in six English-language journals issued by societies related to cardiovascular medicine in Japan. All these journals had been indexed in PubMed for more than 5 years until 2015. We examined the 2-year trends in the prevalence of RCTs, as well as the types of study subjects and interventions investigated. In addition, we applied a multivariable logistic regression analysis to assess the factors related to the publication of RCTs. A total of 7117 articles were eligible for our analyses. The proportion of RCTs among Japanese journals was 3.5% (252/7117). No significant change in the prevalence of RCTs among all included journals was noted (3.8% vs 3.1%, p=0.751). RCTs related to ischaemic heart disease were the most frequently published (85/252, 33.7%). In the multivariable analysis, a male first author (adjusted OR (AOR) 1.97; 95% CI 1.30 to 2.99) and reports from Asia (AOR 1.62; 95% CI 1.19 to 2.21) were significantly associated with the publication of RCTs.

In Japanese cardiovascular journals, RCTs accounted for 3.5% of all original research articles published, and there was no change in the prevalence of RCTs during the study period.