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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.
On 1st January 1982, the first great epidemiological study in Brazil began in Pelotas. The young Doctors Fernando Barros and Cesar Victora were responsible for developing a kind of research that was only made in European countries or in the United States, due to the follow-up difficulties and the high expenses.
The study, known as 1982 Birth Cohort, is about the follow-up of all children who were born at Pelotas’ hospitals in 1982. Altogether, there were 5.914 alive newborns, whose mothers lived in the urban area of the city. The research’s goal, by that time, was to evaluate the influence that inherent factors in the children’s period of birth had on their childhood health. Those factors included, among others, the health conditions of the mother and the baby, the baby’s weight when he/she were born, the feeding, the environmental conditions in which the family lived (sanitation and habitation), and the quality of medical assistance that the children used to receive.
The central hypothesis of the study was that the health of Brazilian children, from a country with so many inequalities, should be based on the social reality understanding.
This pioneering research was so well accepted by the scientific community that, in the year after its beginning, the World Health Organization (WHO) provided funding for the realization of the first follow-up after the births. Then, other international organizations became interested in the project. The 1982 Birth Cohort became a world reference and gathered important researchers of different health areas.
With so much interest of the many world science sections, the 1982 Birth Cohort study was beyond their initial research expectations on children health. All the 1982 births of Pelotas keep being followed until now. The research, now, aims the evaluation about the influence of the birth inherent factors in the adolescents and adults lives.
At some moment, while the first field visits to the 1982 Birth Cohort participants were occurring, the researchers planned to start a new birth cohort study. The central objective was to allow a comparison of temporal trends in the maternal and child populations’ features, and in their main health indicators. With the European Economic Community funding, the new study was organized to start in 1993. And, like the 1982 Birth Cohort, the 1993 Birth Cohort has been following all births of Pelotas in 1993 until now.
In order to know the natural history of the populations and to analyse what changes over time, it was developed a new birth cohort study in 2004, following the same distance period of the 1982 Birth Cohort to the 1993 Birth Cohort.
The 1982 Birth Cohort participants and their families had a very important role in the history building of the health science in Brazil and worldwide. Through those people willingness, the scientific community obtained information about the 1982 neonates that official organizations did not know about. An example is the number of births in 1982, since the Health Department of Pelotas had registered less 562 births than the amount identified by the Center of Epidemiological Research (CPE). The numbers relating to child mortality were also very different.
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.
Birth period and the first year of life period
Births:
Birth weight:
Smoking mothers:
Smoking:
Breastfeeding:
Data about Mortality
Mortality:
Child Mortality:
Main causes of death:
Adulthood
Schooling:
Job
Salary
Sexuality:
Children:
Body weight evaluation:
Smoking
Inheritance of smoking:
The 1982 Birth Cohort of Pelotas is the largest epidemiological longitudinal study realized in Latin American countries. The research was conducted in stages, and the first one was called Perinatal Study. At this stage, all the births, during the period of January and December of Pelotas’ hospitals were identified. There were 7.392 births, but, since the research should focus only on babies who were born alive and whose mothers lived in the urban area of Pelotas, there were 5.914 able babies to participate in the study.
Follow-up studies:
In 1982, doctors of the Center of Epidemiological Research (CPE) team visited daily the three maternity hospitals of the city in order to interview the mothers that had given birth and looked at the newborns. The mothers were interviewed about a series of biological, demographic, socioeconomic and assistance factors. The neonates’ data included sex, singleton or twin pregnancy, gestational age, perinatal morbidity and mortality and type of parturition. The mothers were weighted and measured before parturition, and the babies were weighted just after their births. The team who did this job was previously trained in a pilot study.
After this identification stage, many follow-up visits to the babies and their mothers happened.
1983 – It was realized a follow-up analysis of all about-12-month babies who were born between January and April of 1982. At this moment, it was used the data informed by the mothers at the hospital. Of the 1.916 searched participants, 1.457 children were found, and this fact represented a loss of 20%. In this follow-up study, the children were weighted and measured, and their mothers or sponsors were interviewed about their socioeconomic, environmental, and demographic features, as well as about features related to their diet, hospital morbidity, and health services use.
1984 – It was realized a census of all the 68.590 houses of Pelotas in order to find all 1982 born children. The initiative aimed to reduce the loss of 20% that happened in 1983. This follow-up analysis found 4.933 children, which meant a loss of 12,8% instead. Through the census, it was possible to know that 45% of the families had changed their addresses inside the city, since the first contact two years before. In this second follow-up, children were weighted and measured and their mothers were also interviewed again. Besides the questions asked on the previous follow-up, the researchers collected information about some common diseases and the children’s psychomotor development. They also collected data about the mothers’ health, and all those data were connected to the information already gathered in the perinatal study and in the first follow-up analysis.
1986 – It was realized a new census of all houses of Pelotas. The fieldwork lasted from December 1985 to April 1986 and the children were, in average, 43 months old. 4.742 children were found, which represented 84,1% of all participants. Again, socioeconomic, demographic, environmental and food factors were investigated. Among the new elements of this follow-up analysis was a brief interview with the children.
1995 – It was realized a follow-up with 20% of the 1982 Birth Cohort. The location method used was the same as the previous follow-up data. 715 participants were found, and they were, in average, at the age of 13.
1996 – It was realized a follow-up with 27% of the 1982 Birth Cohort. 1.597 adolescents were searched, but only 1.076 of them were found. Their average age was of 14,7 years.
1997 a 2001 – It was realized an ethnographic study with 96 participants of the 1982 Birth Cohort, who were between 15 and 19 years old.
2000 – It was realized a follow-up with all the young-man participants. Their identification was made through the Brazilian conscription. 3.037 participants were waited, but only 2.250 of them were found, which is believed to be the total number of male participants who lived in Pelotas at that time. In this follow-up, all questionnaires made about the current socioeconomic conditions, life habits (smoking, drugs, and physical activity), diet, work, morbidity, education, medication use, sexuality, mental health, and health services use. Through these data, it was possible to evaluate the relationship between respiratory diseases and low birth weight and intrauterine growth retardation.
2001 – It was realized a research with 27% of the 1982 Birth Cohort participants, when 1.031 participants at the average age of 18,9 years were interviewed.
2004-05 – It was realized a census of 98 thousand houses from Pelotas to find all 1982 Birth Cohort participants. 4.297 participants were found, at the average age of 22,8 years. In this follow-up, 282 deaths were detected since their births. Besides the standard questionnaire, there was a blood-sample collection of 3.914 people (91,1% of all participants). Through this initiative, it was created the 1982 Birth Cohort DNA Database.
The details about the 1982 Birth Cohort studies are presented in innumerous scientific articles, which have been written by the CPE researchers, 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
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