Prevalence of Same-Gender Sexual Behavior and HIV in a Probability Household Survey in Mexican Men - Statistical Data Included

Journal of Sex Research, Feb, 2000 by Jose A. Izazola-Licea, Steven L. Gortmaker, Kathryn Tolbert, Victor De Gruttola, Jonathan Mann

For more than a decade the impact of the human immunodeficiency virus (HIV) infection has been felt in many countries. Mexico is not an exception, and AIDS is among the leading causes of death in the young adult population. The fact that HIV is mainly transmitted by sexual activity makes it imperative that we have a better understanding of sexual behavior, in order to be able to favorably influence the trend of the epidemic.

Case reports suggest that the epidemiological pattern of AIDS in Latin America is different from that observed in other parts of the world. Within this region, Mexico seems to have unique characteristics (Mann, Tarantola, & Netter, 1992; Valdespino, Izazola, & Rico, 1988); 95% of the cases to date among men and 45% among women are due to sexual transmission. Among men with sexually acquired AIDS, 60% were classified as homosexuals, 25% as bisexuals, and 15% as heterosexuals. HIV transmission due to injection drug use is negligible in Mexico ([is less than] 1% of reported cases). As of December 31, 1994, 20,796 AIDS cases had been reported in Mexico, most of which have occurred in men (85%), and in Mexico City (56%) (Instituto Nacional de Diagnostico y Referencia Epidemiologicos [INDRE], 1995).

Scientific reports of same-gender sexual behavior and risks for HIV in Spanish-speaking countries are rare. Available reports on male sexual behavior in Mexico, and concerning men in general from Latin-America and Mediterranean countries, have suggested that a substantial number of men engage in homosexual practices, and that most of these men sustain mainly heterosexual relationships (i.e., they are behaviorally bisexual) (Boulton, 1991; Carrier, 1985). It has been hypothesized that a high prevalence of bisexual behavior will have a major impact on the risk of HIV infection among women and children (Carrier, 1989).

A previous study in six Mexican cities documented substantial bisexual behavior among men interviewed in a cross-sectional convenience sample of gay gathering places (Izazola et al., 1991). Because the study of sexual behavior using population-based probability sampling has been rare, convenience surveys of sexual behavior have frequently been the main sources for estimates for the planning of AIDS-related activities (Turner, Miller, & Moses, 1989).

Projections of the AIDS epidemic and design of intervention strategies critically depend on accurate estimates of the magnitude and distribution of the population engaging in risky sexual behavior. Therefore, we conducted a study to provide quantitative population-based estimates of adult males who engaged in exclusive same-gender behaviors and in bisexual behaviors, to estimate HIV-1 prevalence and to discuss implications for HIV-1 sexual transmission in a population with low injection drug use.

METHODS

Data Collection

A household probability survey was carried out in the Mexico City metropolitan area (MCMA) from June 1992 to March 1993. A sampling framework of sanitary jurisdictions from the National Health Surveys System of the Mexican Ministry of Health was used, which employs a multi-stage stratified probability area sampling design. The primary sampling units were clusters of blocks (equivalent to census tracks in the United States). Compact segments of 10 contiguous households were drawn using a systematic selection procedure.

A household listing was performed as the first step of the survey in order to obtain a census of all persons living in each household. Sociodemographic information was collected: age, gender, relationship to the head of the household, schooling, and occupation. For eligible men, information about living with a stable female partner or with their children was also obtained. Respondents were asked to participate in this health survey without being told that AIDS or sexual behavior was the focus of the questionnaire, since these topics were not included in the household listing. Interviewers were instructed to obtain the household information from the first adult found in the selected households.

Informed consent to participate in a survey of sexual behavior and to potentially donate blood and saliva for HIV-1 screening was obtained. Households were revisited up to 10 times. Face-to-face interviews were carried out among eligible individuals using a 25-minute structured questionnaire. Since inquiring about sexual behavior is socially sensitive, interviewers were instructed to question the respondent alone. If the conditions of the interview did not guarantee confidentiality, the interviewers were instructed to postpone or terminate the interview.

An initial total of 13,057 households were included in the sampling frame. One third of the households were excluded for several reasons: vacancy at the time of the survey (13%), not being a household at the time of the survey (6%), nonresponse to the household interview (1.6%), and having no eligible men between 15 and 60 years old in the household (13%). Consequently, 8,759 households were considered eligible, and 13,713 men between 15 and 60 years old lived in these households. Of these, 8,600 (63%) were able to be contacted on a person-to-person basis and were asked to respond to the individual questionnaire: 532 (6%) refused to answer the questionnaire and 8,068 (94%) were successfully interviewed. The overall response rate of this survey (59%) was lower than the national response rate found in a 1993 multipurpose national survey of chronic diseases in Mexico that used the same sampling framework (response rate = 67%). In this survey, the lowest response rate obtained was for males living in Mexico City (64%) (Secretaria de Salud, 1994).