Background: Little is known about the recent proportion and trends of randomised controlled trials (RCTs) published in Japanese cardiovascular journals.
Methods and results: 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.
Conclusions: 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.
Keywords: Japanese cardiovascular journal; prevalence; randomized controlled trials.