RESUMO
OBJECTIVE: To assess non-participation bias in a survey of male sexual behavior. MATERIAL AND METHODS: A household survey was carried out in 1992-1993 using a probability sampling frame in Mexico City. Demographic variables were available for all eligible men. The extent of non-participation bias was estimated using a version of the Heckman method, which utilizes two equations, one to predict participation and the other to predict reports of same-gender sexual behavior. RESULTS: A total of 8,068 of the 13,713 eligible men completed a face-to-face questionnaire (response rate 59%); 173 men (2.1%) reported bisexual behavior in their lifetime, and 37 (0.4%) reported only male partners. Survey participation was predicted using demographic variables: 67% of the observations were correctly predicted by a probit regression model: 82% of participants and 53% of non-participants (pseudo-r2 = 0.13). Same-gender sexual behavior was predicted by variables indicating attachment to gay/bisexual social networks, history of sexually transmitted diseases, positive attitudes towards gay and bisexual males, and lack of support from male relatives. Ninety-seven per cent of the cases was correctly predicted by the probit model (pseudo-r2 = 0.14). The correlation between these two equations was not statistically significant. CONCLUSIONS: These results indicate that prevalence estimates of same-gender sexual behavior among Mexico City men were not biased by selective survey participation. Careful selection and training of household interviewers may have assisted in minimizing potential bias.
Assuntos
Homossexualidade Masculina/estatística & dados numéricos , Adolescente , Adulto , Coleta de Dados , Humanos , Masculino , México , Pessoa de Meia-Idade , Probabilidade , Viés de SeleçãoRESUMO
Conditions of infant and child survival in Mexico have improved considerably over the last 60 years. Infant mortality rates were reduced from more than 250 deaths per 1,000 infants born alive in 1929-1931, to a rate of less than 50 in the period 1982-1987, a figure which still places Mexico among the countries with a high infant mortality rate. Though improvements in the living conditions of the population have undoubtedly played a part in the reduction of infant and child mortality, the early introduction of sanitation campaigns and, more recently of immunization, antibiotics and other modern health techniques have probably been more important. Health services have been extended throughout the country. However, significant portions of the population, especially in the rural areas, but also in the growing urban marginal ones, are to a large extent underserved. As a result, great inequalities in the health status of the population and in their access to health services remain. The problem of providing services to the whole population has become aggravated by the economic and financial crisis which has plagued Mexico since 1982. Reduced revenues for exports and the high cost of servicing the external and the internal debt have significantly decreased government revenues. As a result, public resources directed to health-related services diminished by 50 per cent in real terms between 1982 and 1987. This trend has to be reversed through enforced measures directed to the mobilization of untapped external and internal resources. But improving the conditions of child survival in Mexico requires more than financial resources. It is necessary to integrate and coordinate the fragmented services offered by the government, to give a much higher priority to preventive measures, and to research and to the adequate training of professionals and paraprofessionals in order to re-orient the health system for serving the real needs of the more underprivileged groups of the population (understanding and respecting their cultural beliefs and practices). In this way, Mexico can reverse the trend toward greater inequality which pervades the present system.