Cohort studies have become widely used in epidemiology from the second half of the twentieth century mainly to investigate the natural history of non-transmissible chronic diseases and to respond to the new challenges posed by changes in patterns of morbidity and mortality in developed countries.

The cohort design has made significant contributions to the knowledge on risk factors of chronic diseases and is key to the formulation of public health policies (Szklo, 1998).³3. Szklo M. Population-based cohort studies. Epidemiol Rev. 1998;20(1):81-90.

In Brazil the field of epidemiology has experienced significant growth in the last 20 years parallel to health sciences research strengthening (Meneghini, 2010).²2. Meneghini R. Visibilidade internacional da produção brasileira em saúde coletiva. Cad Saude Publica. 2010;26(6):1058-9. DOI:10.1590/S0102-311X2010000600001
https://doi.org/10.1590/S0102-311X201000... This growth was largely a result of public policies for academic research improvement, especially through expanded graduate programs.

As part of this process, working groups of researchers with expertise on chronic diseases were formed in many Brazilian universities. In the mid-2000s six research groups from across the country came together to develop the Brazilian Longitudinal Study for Adult Health (ELSA-Brasil). Supported by the Brazilian government ELSA-Brasil is the first multicenter cohort study focusing on cardiovascular diseases and diabetes melllitus in adults conducted in Brazil (Aquino et al, 2012).¹1. Aquino EM, Barreto SM, Bensenor IM, Carvalho MS, Chor D, Duncan BB, et al. Brazilian Longitudinal Study of Adult Health (ELSA-Brasil): objectives and design. Am J Epidemiol. 2012;175(4):315-24. DOI: 10.1093/aje/kwr294
https://doi.org/10.1093/aje/kwr294... A detailed description of the process that led to the implementation of ELSA-Brasil can be found in the introduction of this study published in this supplement.

This supplement of Revista de Saúde Pública aims to share the ELSA-Brasil experience with other health researchers. The approaches adopted in the project's main steps are discussed offering input to other national research groups potentially interested in developing cohort studies.

The topics covered in this issue contemplate the following steps of the research project: (i) planning and implementation of the multicenter longitudinal study including communication with subjects and recruitment strategies, ethical issues, questionnaire development, medical assessments and interviews, as well as the publications Committee; (ii) exposure and outcome assessments including medical assessments and measurements, central laboratory set-up and logistics of sample collection and analyses, creation of a biobank, strategies for monitoring and investigating incident outcomes and for voluntary participation and retention in longitudinal studies; (iii) quality of assessments with a review of articles that address data management in multicenter studies, data quality control and assurance strategies including reproducibility of blood pressure measures, cross-cultural adaptation and reliability of self-reported neighborhood characteristics. In addition, an article on the challenges with the import of medical equipment was also included.

We definitely believe this supplement of Revista de Saúde Pública will encourage the exchange of expertise and experience between researchers and contribute to strengthening Brazil's position as a major hub of epidemiological research of great complexity and broad scope, as well as serve as reference and encourage the work of young researchers in epidemiology.

References

Publication Dates