RESUMEN
This is one of a series of monographs on research design and analysis. The purpose of this article is to describe a set of statistical procedures or techniques used to develop and test structural models that characterize the relationships and interrelationships between a group of concepts and variables. These procedures include multiple regression, exploratory and confirmatory factor analysis, path analysis, and structural equation modeling. The article describes the purpose of each of these procedures and how they relate to and build on one another. It also covers the different types of variables examined, including the distinction between endogenous, exogenous, and mediating variables, along with the distinction between measured and unmeasured (or latent) variables. Each procedure results in a set of statistical estimates, and the article presents the interpretation of these estimates, including regression coefficients (standardized and unstandardized), path coefficients, factor loadings, and coefficients of determination (or R2 values). The article presents examples of how each procedure has been used in practice, along with additional resources for readers who wish to learn more.
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Dietética , Humanos , Análisis de Clases Latentes , Análisis Factorial , Análisis MultivarianteRESUMEN
This monograph focuses on understanding statistical and clinical significance and is one in a research and statistics series published by the statistical team of the Journal of the Academy of Nutrition and Dietetics. The content covers the research questions, definition of clinical significance, hypothesis testing, P values, effect sizes, sample sizes, CIs, power analyses, minimal clinically important differences, and validity. This monograph concludes with a summary of the importance of clinical and statistical results for credentialed nutrition and dietetics practitioners to consider when assessing statistical and clinical significance. The assessment will help readers make subjective clinical judgments in the application of research findings based on their experience.
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Dietética , Academias e Institutos , Dietética/métodos , Humanos , Estado Nutricional , Proyectos de Investigación , Tamaño de la MuestraRESUMEN
Several countries have implemented "family-centered" abstinence-only policies for teenagers, as opposed to encouraging utilization and expansion of reproductive health services and education. Little is known, however, about the effects of these more restrictive policies on adolescent birth rates at the national level or their differential effects by race and ethnicity. The extant literature is even scarcer in low- and middle-income countries. We analyze an unexpected policy change in Ecuador that abruptly reversed course and restricted reproductive health services for teenage women in 2014. We use a canton- and time-fixed effects difference-in-differences analysis of Ecuador's 221 cantons with time-varying controls to analyze the impact of the abrupt policy change on the difference of teen (15-19 years) minus young adult (20-24â¯years) birth rates. In a difference-in-difference-in-differences analysis, the policy change increases birth rates by 8.5 births per 1000 women in cantons with higher indigenous concentration. Results are robust to changes in the comparison population (young adults vs. women in their late 20â¯s or in their early 30â¯s), pre-intervention control periods, population weighting, serial correlation, logarithmic model specification, adjustments for intervention year, definition of indigenous concentration, and potential delays in policy implementation.
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Tasa de Natalidad , Embarazo en Adolescencia , Adolescente , Ecuador/epidemiología , Femenino , Política de Salud , Humanos , Embarazo , Salud Reproductiva , Adulto JovenRESUMEN
BACKGROUND: Uruguay, a South American country of 3.4 million inhabitants that has already banned tobacco advertising, prohibited such terms as light, mild and low-tar and required graphic warnings covering 80% of cigarette packs, is considering the imposition of plain, standardised packaging. METHODS: We conducted an experimental choice-based conjoint analysis of the impact of alternative cigarette package designs on the risk perceptions of 180 adult current Uruguayan smokers. We compared plain packaging, with a standardised brand description and the dark brown background colour required on Australian cigarette packages, to two controls: the current package design with distinctive brand elements and colours; and a modified package design, with distinctive brand elements and the dark brown background colour. Graphic warnings were also varied. RESULTS: Plain packaging significantly reduced the probability of perceiving the stimulus cigarettes as less harmful in comparison to the current package design (OR 0.398, 95% CI 0.333 to 0.476, p<0.001) and the modified package design (OR 0.729, 95% CI 0.626 to 0.849, p<0.001). CONCLUSIONS: Plain packaging enhanced the perceived risk of cigarette products even in a highly regulated setting such as Uruguay. Both the elimination of distinctive brand elements and the use of Australia's dark brown background colour contributed to the observed effect.
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Embalaje de Productos/normas , Medición de Riesgo , Fumadores/psicología , Productos de Tabaco , Adulto , Anciano , Femenino , Humanos , Masculino , Persona de Mediana Edad , Etiquetado de Productos , Uruguay , Adulto JovenRESUMEN
OBJECTIVE: To evaluate the impact of a complete smoking ban in enclosed spaces on the incidence of acute myocardial infarction in Chile. METHODS: The population-based study involved residents of urban areas, where 80% of the Chilean population live, aged 20 years or older who had a myocardial infarction. Monthly myocardial infarction incidence and mortality rates at health-care facilities between January 2011 and December 2014 were derived from admission and mortality databases. Regression discontinuity methods were used to estimate the near-immediate impact on disease incidence of enforcing smoke-free legislation in March 2013. The same analysis was performed for ischaemic stroke, degenerative disc disease and colon cancer. Data on the concentration of fine respirable particulates were included in an additional analysis of myocardial infarction incidence in the Santiago metropolitan area. RESULTS: The enforcement of smoke-free legislation was associated with an abrupt, near-immediate decline of 0.639 cases of myocardial infarction per 100 000 adults per month (95% confidence interval, CI: 0.242 to 1.036; relative decline: 7.8%). Similar declines were observed in men and women and in people aged over and under 70 years. However, enforcement of the legislation was not associated with a significant change in the rate of ischaemic stroke, degenerative disc disease or colon cancer. The abrupt decline in myocardial infarction incidence was also observed when data on fine respirable particulates were included in an analysis for Santiago. CONCLUSION: The enforcement of extensive smoke-free legislation in Chile was associated with an abrupt, near-immediate decline in the incidence of myocardial infarction.
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Infarto del Miocardio/epidemiología , Política Pública , Política para Fumadores/legislación & jurisprudencia , Fumar/legislación & jurisprudencia , Contaminación por Humo de Tabaco/legislación & jurisprudencia , Adulto , Anciano , Chile/epidemiología , Femenino , Humanos , Incidencia , Masculino , Persona de Mediana Edad , Programas Nacionales de Salud , Fumar/efectos adversos , Contaminación por Humo de Tabaco/efectos adversos , Adulto JovenRESUMEN
We analyzed a nationwide registry of all pregnancies in Uruguay during 2007-2013 to assess the impact of three types of tobacco control policies: (1) provider-level interventions aimed at the treatment of nicotine dependence, (2) national-level increases in cigarette taxes, and (3) national-level non-price regulation of cigarette packaging and marketing. We estimated models of smoking cessation during pregnancy at the individual, provider and national levels. The rate of smoking cessation during pregnancy increased from 15.4% in 2007 to 42.7% in 2013. National-level non-price policies had the largest estimated impact on cessation. The price response of the tobacco industry attenuated the effects of tax increases. While provider-level interventions had a significant effect, they were adopted by relatively few health centers. Quitting during pregnancy increased birth weight by an estimated 188 g. Tobacco control measures had no effect on the birth weight of newborns of non-smoking women.
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Publicidad/legislación & jurisprudencia , Peso al Nacer/fisiología , Regulación Gubernamental , Embalaje de Productos/legislación & jurisprudencia , Cese del Hábito de Fumar , Productos de Tabaco/legislación & jurisprudencia , Adolescente , Femenino , Promoción de la Salud/métodos , Humanos , Embarazo , Sistema de Registros , Impuestos , Productos de Tabaco/economía , UruguayRESUMEN
BACKGROUND: In 2005, Uruguay initiated a series of comprehensive anti-smoking measures. We aimed to assess the effect of Uruguay's 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: Uruguay's 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.
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Política de Salud , Cese del Hábito de Fumar , Adolescente , Adulto , Argentina/epidemiología , Conductas Relacionadas con la Salud , Encuestas Epidemiológicas , Humanos , Fumar/epidemiología , Uruguay/epidemiología , Adulto JovenRESUMEN
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 women's 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 household's 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 women's 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 woman's 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.
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Promoción de la Salud/organización & administración , Accesibilidad a los Servicios de Salud , Servicio de Ginecología y Obstetricia en Hospital/estadística & datos numéricos , Atención a la Salud/economía , Bienestar Materno , México , Modelos Econométricos , Encuestas Nutricionales , Estudios de Casos Organizacionales , Pobreza , Evaluación de Programas y Proyectos de SaludRESUMEN
INTRODUCTION: Although investment in HIV/AIDS prevention has increased worldwide, it remains uncertain how the additional resources can be most efficiently allocated to maximize the number of infections averted, especially at the country, regional and local levels. METHODS: Data from developing countries in Africa, Asia and Latin America were reviewed on the allocation of HIV/AIDS prevention funds in relation to the prevalence of infection, as well as budgetary allocations for specific population groups at high risk of infection, such as sex workers, intravenous drug users and men who have sex with men. The variation in unit costs of voluntary counselling and testing in five countries was also examined. RESULTS: Evidence was found of three distinct sources of inefficiency in the allocation of HIV/AIDS prevention resources: inefficiency in the mix of interventions selected; inefficient targeting of key populations; and technical inefficiency in the production of HIV prevention services. CONCLUSION: A general conceptual framework for evaluating the efficiency of HIV/AIDS prevention programmes at the country, regional and local levels is proposed. This framework stresses three equally important components of programme efficiency: cost-effectiveness (the choice of the mix of interventions); targeting (the choice of the mix of target populations); and technical efficiency (the delivery of prevention services at least cost).