Jeffrey E. Harris

Bayes Methods for Combining the Results of Cancer Studies in Humans and other Species

Abstract We propose a class of Bayesian statistical methods for interspecies extrapolation of dose-response functions. The methods distinguish formally between the conventional sampling error within each dose-response experiment and a novel error of uncertain relevance between experiments. Through a system of hierarchical prior distributions similar to that of Lindley and Smith (1972), the dose-response data from many substances and species are used to estimate the interexperimental error. The data, the estimated error of interspecies extrapolation, and prior biological information on the relations between species or between substances each contribute to the posterior densities of human dose-response. We apply our methods to an illustrative problem in the estimation of human lung cancer risk from various environmental emissions.

Heterogeneous Impact of the “Seguro Popular” Program on the Utilization of Obstetrical Services in Mexico, 2001–2006: A Multinomial Probit Model with a Discrete Endogenous Variable

OBJECTIVE We evaluated the impact of Seguro Popular (SP), a program introduced in 2001 in Mexico primarily to finance health care for the poor. We focused on the effect of household enrollment in SP on pregnant womens access to obstetrical services, an important outcome measure of both maternal and infant health. DATA We relied upon data from the cross-sectional 2006 National Health and Nutrition Survey (ENSANUT) in Mexico. We analyzed the responses of 3890 women who delivered babies during 2001-2006 and whose households lacked employer-based health care coverage. METHODS We formulated a multinomial probit model that distinguished between three mutually exclusive sites for delivering a baby: a health unit specifically accredited by SP; a non-SP-accredited clinic run by the Department of Health (Secretaría de Salud, or SSA); and private obstetrical care. Our model accounted for the endogeneity of the households binary decision to enroll in the SP program. RESULTS Women in households that participated in the SP program had a much stronger preference for having a baby in a SP-sponsored unit rather than paying out of pocket for a private delivery. At the same time, participation in SP was associated with a stronger preference for delivering in the private sector rather than at a state-run SSA clinic. On balance, the Seguro Popular program reduced pregnant womens attendance at an SSA clinic much more than it reduced the probability of delivering a baby in the private sector. The quantitative impact of the SP program varied with the womans education and health, as well as the assets and location (rural vs. urban) of the household. CONCLUSIONS The SP program had a robust, significantly positive impact on access to obstetrical services. Our finding that women enrolled in SP switched from non-SP state-run facilities, rather than from out-of-pocket private services, is important for public policy and requires further exploration.

FIELD TESTING AND COMPARATIVE EVALUATION OF RAPID, VISUALLY READ SCREENING ASSAYS FOR ANTIBODY TO HUMAN IMMUNODEFICIENCY VIRUS

Five rapid, visually read assays for detection of antibody against human immunodeficiency virus (HIV) were evaluated on fresh serum samples from 4000 prospective blood donors at Mama Yemo Hospital, Kinshasa, Zaïre. The sensitivity of the assays, based on 214 specimens positive by western blot, ranged from 84.6% to 99.1%. The specificity, based on 3664 samples negative by enzyme-linked immunosorbent assay (ELISA) or western blot, ranged from 92.7% to 98.8%. Three readers scored each test result independently; disagreement about test interpretation occurred in 1.2-8.3% of the specimens. There was no correlation between assay performance and assay principle (agglutination or dot immunobinding) or antigen source (viral lysate or recombinant). Assays such as these can be readily implemented in a developing country transfusion centre, where blood screening by ELISA is not practicable.

Tobacco control campaign in Uruguay: a population-based trend analysis.

BACKGROUND In 2005, Uruguay initiated a series of comprehensive anti-smoking measures. We aimed to assess the effect of Uruguays anti-tobacco campaign. METHODS We did a population-based trend analysis, using neighbouring Argentina, which has not instituted such extensive anti-tobacco measures, as a control. We assessed three key endpoints in both countries: per-person consumption of cigarettes, as measured by tax records; the prevalence of tobacco use in adolescents, as measured by school-based surveys; and the prevalence of tobacco use in adults, as measured by nationwide household-based surveys. FINDINGS During 2005-11, per-person consumption of cigarettes in Uruguay decreased by 4·3% per year (95% CI 2·4 to 6·2), whereas per-person consumption in Argentina increased by 0·6% per year (-1·2 to 2·5; p=0·002 for difference in trends). During 2003-09, the 30-day prevalence of tobacco use in Uruguayan students aged 13 years, 15 years, and 17 years decreased by an estimated 8·0% per year (4·5 to 11·6), compared with a decrease of 2·5% annually (0·5 to 4·5) in Argentinian students during 2001-09 (p=0·02 for difference in trends). From 2005 to 2011, the prevalence of current tobacco use in Uruguay decreased annually by an estimated 3·3% (2·4 to 4·1), compared with an annual decrease in Argentina of 1·7% (0·8 to 2·6; p=0·02 for difference in trends). INTERPRETATION Uruguays comprehensive tobacco-control campaign has been associated with a substantial, unprecedented decrease in tobacco use. Decreases in tobacco use in other low-income and middle-income countries of the magnitude seen in Uruguay would have a substantial effect on the future global burden of tobacco-related diseases. FUNDING J William Fulbright Foreign Scholarship Board and the US Department of State.

Reporting Delays and the Incidence of AIDS

Abstract It can take several months, and often years, for case reports of acquired immunodeficiency syndrome (AIDS) to be received by the Centers for Disease Control (CDC). As a result, the cumulative number of AIDS cases reported by the CDC at a given date may fall considerably below the actual number thus far diagnosed. Methods are described for estimating both the probability distribution of reporting delays and the actual incidence of AIDS. An estimated 62% of AIDS cases are reported more than 2 months after diagnosis, and 17% are reported with a delay of 3 years or more. An estimated 130,000 AIDS cases were actually diagnosed through March 1989, compared to about 91,000 cases reported by that time. There has been an increase in reporting delays during 1982–1989, as well as significant geographic variation in reporting delays. The actual incidence of AIDS is found to be rising most rapidly in nonurban regions and metropolitan areas with less than one million population. A model of AIDS incidence based...

Pricing Rules for Hospitals

The widespread cross subsidization observed in hospital rate structures has become the focus of increasing controversy. This paper shows how this pricing practice can play a critical role in compensating for distortions and inequalities in existing health insurance coverage. The hospital pricing decision is modeled as a problem in public enterprise pricing. Theoretically derived prices are then compared with those charges actually observed in a representative hospital. Cross subsidization among ancillary services, special procedures, and daily accommodations is found to have potentially significant welfare gains. These results suggest that the frequently cited norm of average cost pricing in hospitals may have serious drawbacks.

Asymmetric peer effects in the analysis of cigarette smoking among young people in the United States, 1992-1999.

We extend the recent literature on peer effects to test the possible role of asymmetric social influences in the determination of youth smoking. We analyzed cigarette smoking among people aged 15-24 in approximately 90,000 households in the 1992-1999 U.S. Current Population Surveys. The presence of additional smoking sibling in a household, we estimated, raised a young persons probability of smoking by 7.6%, while each non-smoking sibling lowered the probability by an estimated 3.5%. Moreover, the overall deterrent effect of an increase in cigarette price on the probability of smoking was approximately 60% greater than the estimated effect when peer influences were held constant. The concept of asymmetric social influence may have applications in other fields, including labor economics, education, crime prevention, and group dynamics.

Incomplete compensation does not imply reduced harm: Yields of 40 smoke toxicants per milligram nicotine in regular filter versus low-tar cigarettes in the 1999 Massachusetts Benchmark study

The yields of 40 toxic smoke constituents per mg nicotine were computed in three matched pairs of higher- and lower-tar cigarettes tested in the 1999 Massachusetts Benchmark Study. In the three pairs, 19, 20 and 17 compounds, respectively, exhibited significantly greater yields per mg nicotine in the lower-tar than the corresponding higher-tar brand. Based on the assumption that toxicant yields per mg nicotine were independent of smoking intensity, the minimum degree of nicotine compensation necessary to obtain equal or greater dosages of these toxic compounds from the lower-tar cigarette ranged from 0% to 73%. A smoker who compensates only incompletely for nicotine may thus obtain a higher dosage of a specific smoke toxicant from a lower-tar cigarette than from a higher-tar cigarette. From the toxicological standpoint, incomplete compensation for nicotine does not necessarily translate into harm reduction.

Smoke yields of tobacco-specific nitrosamines in relation to FTC tar level and cigarette manufacturer: analysis of the Massachusetts benchmark study

Objectives. This research assessed the relationship between the deliveries of carcinogenic tobacco-specific nitrosamines (TSNAs) and the Federal Trade Commission (FTC) “tar” ratings of US commercial cigarettes. Methods. Analysis of covariance (ANCOVA) was used to assess the explanatory power of FTC tar, the particular manufacturer, and other cigarette characteristics to predict the yields of four TSNAs (N′-nitrosonornicotine [NNN], 4-(N-methyl-N-nitrosamino)-1-(3-pyridyl)-1-butanone [NNK], N′-nitrosoanatabine [NAT], and N′-nitrosoanabasine [NAB]) in 26 US commercial brands tested in the 1999 Massachusetts Benchmark Study. Results. When FTC tar alone was used to predict TSNA yield, the squared correlation coefficient (R2) was only 38% for NNN, 76% for NNK, 46% for NAT, and 49% for NAB. Inclusion of manufacturer-specific variables significantly (p < 0.001) increased the estimated R2 for three of the four species of nitrosamine to: 78% for NNN, 88% for NNK, and 81% for NAT. Inclusion of other cigarette characteristics (filter type, paper permeability, tobacco weight, tip dilution) did not reduce the significance of the manufacturer-specific effects. Federal Trade Commission nicotine and carbon monoxide (CO) yields were no better at predicting TSNA levels. Conclusions. FTC ratings for tar, nicotine, and carbon monoxide do not tell the entire story about the comparative yields of toxic agents in marketed cigarette brands. The significant manufacturer-specific effects suggest that proprietary blending and processing of tobacco matter as well. Public, brand-by-brand disclosure of the yields of TSNA and possibly other smoke constituents appears to be warranted.

Increasing the federal excise tax on cigarettes

Abstract In the current debate on fiscal policy in the United States, many government officials have advocated an increase in the federal excise tax on cigarettes. Although opponents have argued that tobacco is already far too burdened by state and federal taxation, the case for new increases in federal cigarette levies is in fact strong.