Low- and middle-income countries such as Brazil face a lack of epidemiological data, and one of the key priorities for researchers is developing high-quality surveys. Investigators at Columbia University's Mailman School of Public Health with collaborators at the Federal University of São Paulo studied the difficulties in conducting a longitudinal epidemiological survey in a school-based sample in Brazil. The findings are published online in the journal BMC Psychiatry.

"Overall, researchers in countries like Brazil lack knowledge about the importance of scientific research," said Silvia Martins, MD, PhD, associate professor of Epidemiology at the Mailman School of Public Health. "In particular, there are very few studies assessing the potential impact of social inequalities and exposure to traumatic experiences on psychiatric outcomes at the population level."

Martins and colleagues studied a sample -attending adolescents born in 2002 now in the 7th grade in nine public schools during 2014 in two neighborhoods of in Sao Paulo with different levels of urbanicity. One neighborhood had low exposure to urban violence and scored high on the Human Development Index, while the other experienced high exposure to urban violence and low Index scores. In total, nine located at the most socially vulnerable regions of each neighborhood were selected.

"At the start, we experienced several hardships," said Martins. "These included achieving unbiased sampling, reaching subjects, scheduling interviews, keeping participants' updated contact information, and counting on a highly-trained research team."

Some classes' records contained names of students who had never actually studied in those schools. "Inaccurate lists of enrolled students were a major source of concern," noted Martins. In terms of communications, the researchers found that poor internet access, deficient telephone and postal services also affected results.

"Our study offered some important insights on the problems faced when conducting epidemiological field work in low- and and provides some alternatives on how to deal with these difficulties. Working closely with community leaders, organizing group efforts to perform interviews, using a short, easy to understand instrument and providing a reward for participants are some of the strategies to be used, not only in Brazil, but also in other low- and middle-income countries," observed Martins.