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Cohorts are studies also known as longitudinal studies, which are based on the identification of a group of individuals and on their follow-up over a period of time. The term cohort was created for referring to groups of soldiers who marched together in Roman legions during the Roman Empire.
All children born between January the first and December the thirty-first of 1993, who lived in the urban area of Pelotas, participate in the epidemiological study known as 1993 Birth Cohort. This research was developed by researchers of the Center of Epidemiological Research (CPE) and by the Postgraduate Program in Epidemiology at the Federal University of Pelotas (UFPel).
The 1993 Birth Cohort started 11 years after the realization of the 1982 Birth Cohort. The first cohort was developed through the initiative of Professors Cesar Victora and Fernando Barros together with other researchers. The 1982 Birth Cohort included all 1982 births in Pelotas.
The aim of having two birth cohort studies with the same features, but a decade different, was to enable the comparison between the maternal-child populations’ features and the evolution of the main health indicators. Besides, with those studies, it is possible to evaluate the influence of premature factors that occur during childhood in health in the life cycle.
During the creation of the 1993 Pelotas Birth Cohort, the researchers had the funding of the European Economic Community. However, for the study development until now, a lot of institutions have been contributing, such as the Brazilian Federal Agency for Support and Evaluation of Graduate Education (CAPES), the National Program for Excellence Centers, the National Research Board, the Brazilian Ministry of Health, the National Board for Technological and Scientific Development (CNPq) and the Foundation of Support for Research of Rio Grande do Sul (FAPERGS).
The cohort studies are organized in stages that consist of the participants’ development follow-up analyses. The 1993 Birth Cohort identified 5.249 births of alive babies and it has been following them until now. In all follow-up analyses, researchers collect a series of information that are afterwards analyzed and compared with many other available data of the same person and other participants from the same or other cohorts.
The 5.249 participants of the 1993 Birth Cohort were very important for the development of health research in Brazil. With the willingness of all these people, the scientific community gathered important information about different phases of the participants’ lives, from their habits and their mothers’ health during pregnancy, their development as children and their first adolescence features, to their health as young adults.
CPE is very grateful to the collaboration of all mothers who, a little after their childbirth, accepted to answer a lot of questions to the researchers, and allowed that their newborns were tested for measuring and weight analyses.
More than the collaboration that those mothers gave to the researchers at the hospital, they also gave their addresses and, with no immediate benefit, they have received the researchers a lot of times during many years in order that the researchers could follow their children’s development.
All the available time provided by the mothers and by the own participants, and all the work that the researchers had to find those almost six thousand families along 30 years, are nowadays worth for the scientific knowledge that is available for the population.
Births:
Mother’s age:
Babies Sex:
Parturition:
Cesarean:
Birth weight:
Breastfeeding:
Smoking:
Mortality:
The 1993 Birth Cohort was created in order to propitiate a comparative analysis with the 1982 Birth Cohort data, having a 10-year interval of time between them. Thinking about the great politic and social transformations that have happened in Brazil between the 80s and 90s, the researchers wanted to analyze the evolution of health indicators and social differences.
Initially, the second cohort was planned to begin exactly 10 years after the first one. However, due to a delay in receiving the funding, the study began in 1993, which did not cause any damage related to the data validity. The design of the 1993 Birth Cohort was much more complex than the previous one. Through the 1982 Birth Cohort follow-ups, it was possible to identify that the most important changes in children’s health occur during their first year of life, which guided the concentration of the1993 studies in this period of life. Thus, besides the perinatal study, the 1993 Birth Cohort developed three more follow-up analyses and a specific study in their first year of life.
The perinatal study was similar to the 1982 one. The five maternity hospitals of Pelotas were visited between January the first and December the thirty-first of 1993. 5.265 eligible babies (alive newborns) were identified, but due to 16 refusals (0,3% of all eligible neonates), there were 5.249 participants in total. The mothers were interviewed through a standard questionnaire, which consisted of questions about socioeconomic, demographic, reproductive, behavioral, assistance and health themes. The newborns were analyzed as to identify their birth weight, their height measure and their head circumference.
For the one-month and the three-month follow-up analyses, it was selected a random sample of 13% of the babies. The interviewers visited these families in their houses, where they applied questionnaires and realized anthropometrical exams. In the six-month and 12-month follow-ups, all low birth weight babies (less than 5,5 pounds) were visited, besides more 20% of the other ones, which were again randomly selected.
Between the years of 1993 and 1994, there were also a project about mortality, which included late fetal deaths, neonates and post neonates. All the hospitals, register offices, cemeteries, and the Health Regional Department were regularly visited for detecting participant babies deaths.
Many follow-up studies and specific analyses have been made until nowadays. Generally, the follow-up studies aim at finding socioeconomic, environmental, and demographic features, as well as aspects related to diet, hospital morbidity, and health services use. This model guides the studies conducted by the 1982 Birth Cohort researchers and, so, it allows its comparison with the 1993 studies. However, the 1993 Birth Cohort studies are wider, since there are analyses of lung diseases data, ethnographic studies, analyses of oral and mental health, body composition, and habits such as smoking, alcohol use, and practice of physical and leisure activities.
The details about the 1993 Birth Cohort studies are presented in innumerous scientific articles, which have been written by the researchers of the Center of Epidemiological Research (CPE), and by the students of the Postgraduate Program in Epidemiology at UFPel. You can read some of those papers that are available at open access journals.
The instruments and the questionnaire used in the main follow-up studies and analyses are available for the scientific community.
+55 (53) 3284 – 1300
ppgepi@ufpel.edu.br
Rua Marechal Deodoro, 1160 – 3° Piso
Bairro Centro – Pelotas, RS
Cep: 96020-220 – Caixa Postal 464