From the Roman Empire to the New Millennium. Data access and sharing from healthy ageing cohorts.

Cohort studies are the best way to analyze the incidence and natural history of a disorder, permitting to assess associations between multiple exposures and multiple outcomes. A well-designed cohort may be particularly relevant regarding the study of the ageing processes of adult populations, allowing the study of processes and dynamics of the individual life course and the study of the effects of earlier exposures and characteristics on later outcomes. Moreover, cohort studies seem the best instrument to analyze the factors favoring active and healthy ageing, and to increase knowledge about the most appropriate interventions to enhance older population's wellness. Nonetheless, the number of cohorts on ageing is limited, because they are very expensive to develop, establish, and maintain, requiring long-term investment to be efficiently performed to obtain all the data needed to address the longitudinal research questions. Open data and data sharing should be encouraged to ensure verifiable, reproducible and transparent results, and to allow the generation of new knowledge in the context of earlier discoveries. Making cohort studies "open" can foster the efforts of the scientific community committed in the study of ageing and give a real contribution to the well-being of the ageing population. KEY-MESSAGE:•Cohort studies are the best way to analyze the incidence and natural history of a disorder, the factors favoring active and healthy ageing, and to increase knowledge about the most appropriate interventions to enhance older population's wellness.•Making cohort studies "open" can foster the efforts of the scientific community committed in the study of ageing and give a real contribution to the well-being of the ageing population.