Sexual network position and risk of sexually transmitted infections.

OBJECTIVES: A population-based sexual network study was used to identify sexual network structures associated with sexually transmitted infection (STI) risk, and to evaluate the degree to which the use of network-level data furthers the understanding of STI risk. METHODS: Participants (n = 655) were from the baseline and 12-month follow-up waves of a 2001-2 population-based longitudinal study of sexual networks among urban African-American adolescents. Sexual network position was characterised as the interaction between degree (number of partners) and two-reach centrality (number of partners' partners), resulting in the following five positions: confirmed dyad, unconfirmed dyad, periphery of non-dyadic component, centre of star-like component and interior of non-star component. STI risk was measured as laboratory-confirmed infection with gonorrhoea and/or chlamydia. RESULTS: Results of logistic regression models with generalised estimating equations showed that being in the centre of a sexual network component increased the odds of infection at least sixfold compared with being in a confirmed dyad. Individuals on the periphery of non-dyadic components were nearly five times more likely to be infected than individuals in confirmed dyads, despite having only one partner. Measuring network position using only individual-based information led to twofold underestimates of the associations between STI risk and network position. CONCLUSIONS: These results demonstrate the importance of measuring sexual network structure using network data to fully capture the probability of exposure to an infected partner.

Association of the California Tobacco Control Program with declines in cigarette consumption and mortality from heart disease.

BACKGROUND: The California Tobacco Control Program, a large, aggressive antitobacco program implemented in 1989 and funded by a voter-enacted cigarette surtax, accelerated the decline in cigarette consumption and in the prevalence of smoking in California. Since the excess risk of heart disease falls rapidly after the cessation of smoking, we tested the hypothesis that this program was associated with lower rates of death from heart disease. METHODS: Data on per capita cigarette consumption and age-adjusted rates of death from heart disease in California and the United States from 1980 to 1997 were fitted in multiple regression analyses. The regression analyses included the rates in the rest of the United States and variables that allowed for changes in the rates after 1988, when the tobacco-control program was approved, and after 1992, when the program was cut back. RESULTS: Between 1989 and 1992, the rates of decline in per capita cigarette consumption and mortality from heart disease in California, relative to the rest of the United States, were significantly greater than the pre-1989 rates, by 2.72 packs per year per year (P = 0.001) and by 2.93 deaths per year per 100,000 population per year (P<0.001). These rates of decline were reduced (by 2.05 packs per year per year, [P=0.04], and by 1.71 deaths per year per 100,000 population per year, [P=0.031) when the program was cut back, beginning in 1992. Despite these problems, the program was associated with 33,300 fewer deaths from heart disease between 1989 and 1997 than the number that would have been expected if the earlier trend in mortality from heart disease in California relative to the rest of the United States had continued. The diminished effectiveness of the program after 1992 was associated with 8300 more deaths than would have been expected had its initial effectiveness been maintained. CONCLUSIONS: A large and aggressive tobacco-control program is associated with a reduction in deaths from heart disease in the short run.