How does a cohort work?



As you know, the BiSC project is an epidemiological cohort study. This means that the team follows up volunteers, during which we measure different variables, including exposure to various risk factors and their health outcomes.

In the case of BiSC, the cohort of volunteers is made up of you, the families. The risk factors we measure are numerous, but we focus primarily on urban exposures of mothers during pregnancy, and BiSC children during childhood (environmental pollution, exposure to green spaces and lifestyles). In terms of health outcomes, we collect biological samples to measure different compounds, and we also study child development and the onset of certain disorders, conditions and pathologies.

The aim of our work is to identify which factors may be related to certain outcomes in children’s health. Previous cohort studies have shown, for example, that high maternal blood levels of ferritin during pregnancy can protect against the symptoms of attention deficit hyperactivity disorder [1]. Other examples of interesting findings made through cohorts are that nut intake during pregnancy is associated with improved neurodevelopment during infancy [2] or that breastfeeding favours the cognitive development of infants and could protect them from autistic traits [3].

In general, cohort studies are often expensive and require significant funding to be carried out. The need to cover the monitoring of large numbers of people over long periods of time, to collect data from many sources of information and to require highly specialised staff and equipment make these studies complex to develop. Even so, there are many cohorts that regularly follow up their participants. One example is “Childhood and Environment” (INMA,, a project very similar to BiSC, also led by ISGlobal. This study has been following boys and girls from Sabadell, Valencia, Guipúzcoa, Asturias and Menorca from birth to the present day, and who are between 17 and 20 years old.

To ensure this follow-up, it is common for researchers to seek funding from multiple sources to develop the different parts of these studies. Therefore, at BiSC we apply to various calls for grants and collaborate with other groups in institutions. Through these various resources we pay for each of the tests and visits we carry out.

Most of our funding sources include public funding, through government agencies such as the US National Institutes of Health (NIH), the European Research Council (ERC) or the Ministry of Health. These grants require a highly competitive selection process, in which the agencies consider the trajectory of the researchers, the equipment and time needed, and the potential of the results of scientific production.

It is for this reason that there is often no certainty as to what the future follow-up of the studies will be. The sources that will cover the costs of these visits must be identified, the projects and financial justifications drafted, and the projects must undergo a long and complex process of review and selection before funding is secured. Nevertheless, collaboration between institutions and research groups can ensure the continuity of such research.

BiSC is a very large project with the collaboration of many public institutions and different sources of funding. All of this has led us to have collected data since 2018, and we are very happy to be able to count on you for the follow-up of the 4 years that will begin in April.

In addition to team effort, cohort projects could not exist without the altruistic collaboration of thousands of participants. Thank you for being part of BiSC!


  • Santa-Marina L, Lertxundi N, Andiarena A, et al. Maternal Ferritin Levels during Pregnancy and ADHD Symptoms in 4-Year-Old Children: Results from the INMA-INfancia y Medio Ambiente (Environment and Childhood) Prospective Birth Cohort Study [published correction appears in Int J Environ Res Public Health. 2021 Jun 10;18(12):]. Int J Environ Res Public Health. 2020;17(21):7704.
  • Gignac F, Romaguera D, Fernández-Barrés S, et al. Maternal nut intake in pregnancy and child neuropsychological development up to 8 years old: a population-based cohort study in Spain. Eur J Epidemiol. 2019;34(7):661-673.
  • Boucher O, Julvez J, Guxens M, et al. Association between breastfeeding duration and cognitive development, autistic traits and ADHD symptoms: a multicenter study in Spain. Pediatr Res. 2017;81(3):434-442.


This article was written by Pol Jiménez, PhD student of the BiSC Project.