Aluísio Jardim Dornellas de Barros
Telephone-based surveys are common in developed countries, where practically the entire population has access to fixed telephone lines. The first such survey, the Behavioral Risk Factor Surveillance System (BRFSS), was implemented in the United States in 1981. Initially, it covered only a few areas, but it kept on expanding such that it included 15 states in 1984 and became a national system in 1993.2 The main aim of the system is to collect monthly data on behavioral risk factors that are representative at state level.
In Brazil, the increasing availability of telephones from the 1990s onwards made it possible to start thinking of something similar. The total density of fixed telephone lines (including both residential and commercial lines) went from 6.9/100 inhabitants in 1991 to 39/100 inhabitants in 2001 and reached 99/100 inhabitants in 2008.ª In terms of domestic coverage, results from the Pesquisa Nacional por Amostra de Domicílios (PNAD - National Household Sampling Survey) of 2008 indicate that 44% of the country's homes have a fixed telephone line. However, this proportion varies greatly between states: from 66% in São Paulo to 16% in Alagoas, Southeastern and Northeastern Brazil, respectively. A pilot survey for a telephone-based survey system was conducted in the municipality of São Paulo in 2003, and was named the Sistema de Monitoramento de Fatores de Risco para Doenças Crônicas Não-Transmissíveis (SIMTEL/MSP - Risk Factor Monitoring System for Chronic Non-Transmittable Diseases). It was successfully tested between October and December, when more than 2,000 interviews were held.3
The system tested in São Paulo was adopted by the Ministry of Health and was expanded to all state capitals and the Federal District, starting in 2006, under the new name of Vigilância de Fatores de Risco e Proteção para Doenças Crônicas por Inquérito Telefônico (VIGITEL - Telephone-Based Surveillance of Risk and Protective Factors for Chronic Diseases). Since then, more than 54,000 individuals have been interviewed every year, to obtain a population-based profile of risk factors for chronic diseases. A web page in the Ministry of Health's portal gives details of the system and makes reports and questionnaires available.b
I will not elaborate here on the merits of the need for up-to-date information on the population's risk profile and its evolution. The importance of such information for delineating preventive actions and following up their success is widely recognized. However, there are some fundamental questions to be addressed, regarding the validity of the information obtained through a system like this. The first objection raised by anyone with some degree of knowledge relates to the representativeness of the results, given the enormous inequality of access to fixed telephone lines in Brazil. The domestic coverage of fixed telephone lines varies greatly between the regions, for example, and does not exceed 40% in the north and northeast. To deal with this problem, VIGITEL uses a weighting system that makes it possible to correct the crude estimates obtained.6 Equally importantly, the quality of the estimates obtained through VIGITEL has been evaluated. This showed that in the metropolitan regions presenting lower coverage of fixed telephone lines, there is a potential problem regarding the precision of the estimates.1
Studies have shown that the indicators of the VIGITEL system, such as sedentarism, physical activity and food and drink consumption, are reliable and accurate.5,6 These validation studies are fundamental for allowing the data obtained through the system to be used safely and for their interpretation to be assured.
The data obtained through monitoring systems are important both for health actions and for academic studies. This supplement of the Revista de Saúde Pública brings together 13 articles that examine a variety of topics covered by VIGITEL, going from general matters such as self-assessment of health and healthy behavior to the prevalence of morbid conditions and the coverage of preventive programs. This collection shows the potential of the information gathered, when analyzed creatively and competently.
The speed and cost of this type of survey are unbeatable and make it possible to conduct such surveys frequently (annually in Brazil and monthly in the United States), thus allowing trends to be followed closely. Nonetheless, household surveys are still needed in order to study issues in greater depth, including for the purposes of obtaining anthropometric data, making clinical assessments or collecting blood samples, and this has been discussed in detail.7 Thus, in Brazil today, several national surveys are under preparation or in progress. At the fieldwork stage, there is the Pesquisa Nacional da Avaliação de Impacto da Iodação do Sal (PNAISAL - National Impact Assessment Survey on Salt Iodation). At various stages of management, there are the Inquérito Nacional de Saúde (INS - National Health Survey), Pesquisa Nacional de Utilização de Medicamentos (PNAUM - National Medication Usage Survey) and inquérito nacional de Saúde Bucal (SB - National Oral Health Survey). The forecast is for good times for national health-related data gathering in Brazil!
1. Bernal R, Silva NN. Cobertura de linhas telefônicas residenciais e vícios potenciais em estudos epidemiológicos. Rev Saude Publica. 2009;43(3):421-6. DOI:10.1590/S0034-89102009005000024
2. Mokdad AH. The Behavioral Risk Factors Surveillance System: past, present, and future. Annu Rev Public Health. 2009;30:43-54. DOI:10.1146/annurev.publhealth.031308.100226
3. Monteiro CA, Moura EC, Jaime PC, Lucca A, Florindo AA, Figueiredo ICR, et al. Monitoramento de fatores de risco para doenças crônicas por entrevistas telefônicas. Rev Saude Publica. 2005;39(1):47-57. DOI:10.1590/S0034-89102005000100007
4. Monteiro CA, Florindo AA, Claro RM, Moura EC. Validade de indicadores de atividade física e sedentarismo obtidos por inquérito telefônico. Rev Saude Publica. 2008;42(4):575-81. DOI:10.1590/S0034-89102008000400001
5. Monteiro CA, Moura EC, Jaime PC, Claro RM. Validade de indicadores do consumo de alimentos e bebidas obtidos por inquérito telefônico. Rev Saude Publica. 2008;42(4):582-9. DOI:10.1590/S0034-89102008000400002
6. Moura EC, Morais Neto OL, Malta DC, Moura L, Silva NN, Bernal R, et al. Vigilância de Fatores de Risco para Doenças Crônicas por Inquérito Telefônico nas capitais dos 26 estados brasileiros e no Distrito Federal (2006). Rev Bras Epidemiol. 2008;11(Supl 1):20-37. DOI:10.1590/S1415-790X2008000500003
7. Waldman EA, Novaes HMD, Albuquerque MFM, Latorre MR, Ribeiro MCSA, Vasconcellos M, et al. Inquéritos populacionais: aspectos metodológicos, operacionais e éticos. Rev Bras Epidemiol. 2008;11(Supl 1):168-79. DOI:10.1590/S1415-790X2008000500018
a Agência Nacional de Telecomunicações [Internet]. Brasília: Ministério das Telecomunicações; 1997 [cited 2009 Oct 17]. Available from: www.anatel.gov.br
b Ministério da Saúde. Vigitel. Brasília; 2008 [cited 2009 Oct 17]. Available from: http://portal.saude.gov.br/portal/saude/profissional/area.cfm?id_area=1521