ABSTRACT
BACKGROUND: Lanca perfume (chloroform/ether) is an inhalant used mainly by higher social class students in Brazil. In light of the social and epidemiological features of lanca use, supply, and distribution, this investigation tests hypotheses about the degree to which use of inhalant lanca might be occurring in clusters, consistent with social sharing and diffusion, and might show a direct association with social rank even within the relatively privileged social context of private schools in a large mega-city of Latin America. METHODS: Epidemiologic self-report survey data were from a large representative sample of urban post-primary private school students in São Paulo city, Brazil, in 2008. Newly incident lanca use was studied, first with estimates of clustering from the alternating logistic regressions (ALR) and then with conditional logistic regressions to probe into the hypothesized direct social rank association. RESULTS: ALR disclosed a clustering of newly incident lanca users within private school classrooms (pairwise odds ratio (PWOR)=2.1; 95% CI=1.3, 3.3; p=0.002) as well as clusters of recently active lanca use (PWOR=1.9; 95% CI=1.1, 3.3; p=0.02). Occurrence of lanca use within private school classrooms was directly associated with social rank (odds ratio (OR)=0.2; 95% CI=0.1, 0.8; p=0.03 in the contrast of lowest socio-economic status (SES) versus highest SES strata within classrooms). Thereafter, study of other drugs disclosed similar patterns. CONCLUSIONS: The clustering estimates are consistent with concepts of person-to-person sharing of lanca within private school classrooms as well as other dynamic processes that might promote lanca clusters in this context. An observed direct association with social rank is not specific to lanca use. Direct SES estimates across a broad profile of drug compounds suggests causal processes over and above the more specific initially hypothesized social rank gradients in the lanca diffusion process. A novel facet of the evidence is greater occurrence of drug use among the higher social rank private school students, which should be of interest in the social science community.