Data sharing: a decade since the publication of the first cohort profile

It has been a decade since the section ‘Cohort Profile’ in the International Journal of Epidemiology was launched in December 2004, aiming to foster collaboration through data sharing. To understand the current data sharing practice related to those cohorts, we reviewed 791 subsequent articles which had cited nine early published cohort profiles in 2004/05, each cohort containing data from a single nation. By scrutinizing the methods sections of those articles, we identified 606 articles which had used the original data from the profiled cohorts. Data sharing was indicated if the first/corresponding author’s affiliations of a subsequent article were different from those of the original data holders at the organizational level. As shown in Figure 1, the majority of their subsequent publications (73%, 440/606) were produced by the original teams, and about 27% (166/606) were data-sharing articles led by researchers outside the original data holder’s organizations. Over the past decade, data sharing occurred in eight of the nine profiled cohorts. Although data sharing has occurred, the numbers of data-sharing articles varied considerably among those cohorts, ranging from 0 to 49 articles over a decade. Fewer than half (four of nine) of the cohort