Enfoques modernos del sesgo y la causalidad en la investigación epidemiológica / Modern approaches to bias and causation in epidemiological research

Los conceptos de causalidad y sesgo están en la base de la investigación biomédica moderna, desde el análisis de cientos de factores de exposición, hasta los megaestudios para evaluar intervenciones. Los consumidores de estos productos de la investigación, vemos con desconcierto, que una conclusión que se formula hoy, se pone en duda mañana, y se desecha poco tiempo después, para eventualmente ser retomada en el futuro bajo otras ópticas u otros presupuestos. Aunque no es el único responsable, el sesgo metodológico juega un papel importante como determinante de esta realidad. Este artículo tiene el propósito de destacar el concepto de sesgo, relevante, entre otras posibles acepciones, para la investigación biomédica contemporánea, y su asociación con la definición técnica de confusión, exponer la visión moderna sobre el significado práctico de una causa y examinar críticamente dos modernos recursos analíticos para afrontar el problema del sesgo y la causalidad: los puntajes de susceptibilidad y las variables instrumentales

The concepts of causation and bias are crucial to modern biomedical research, ranging from the analysis of hundreds of exposure factors to megatrials, in order to assess the impact of interventions. As consumers of these research products, we are amazed that a statement made today is put into question tomorrow, discarded afterwards, and eventually retaken in the future from different perspectives or under different assumptions. Although the methodological bias is not the only culprit, it plays an important role as determinant of this reality. This paper intended to clarify the concept of bias, which is relevant, among other possible meanings, to contemporary biomedical research, and its association with the technical meaning of confounding. Other objectives were to present the current vision on the practical meaning of cause in epidemiological causal inference, and to critically review two modern analytical tools to deal with bias and causation such as propensity scores and instrumental variables

Absenteísmo-doença, modelo demanda-controle e suporte social: um estudo caso-controle aninhado em uma coorte de trabalhadores de hospitais, Santa Catarina, Brasil / Sickness-absenteeism, job demand-control model, and social support: a case-control study nested in a cohort of hospital workers, Santa Catarina, Brazil

O objetivo do estudo foi identificar a contribuição do Modelo Demanda-Controle (MDC) e do suporte social para duração do absenteísmo-doença segundo Licenças para Tratamento de Saúde (LTS) nos trabalhadores de hospitais (servidores públicos) da Secretaria de Estado da Saúde de Santa Catarina (SES/SC), Brasil. Entre as secretarias deste estado, a SES/SC tem a segunda maior frequência de LTS, com destaque nos hospitais. Este é um estudo caso-controle aninhado em uma coorte de trabalhadores de hospitais da SES/SC, com acompanhamento entre 01/07/2008 e 30/06/2009. Os casos foram aqueles que apresentaram LTS nesse período, os critérios de pareamento foram sexo, faixa etária e setor de trabalho. O desfecho foi o total de dias de LTS, as variáveis de exposição foram MDC e o suporte social do supervisor e do colega. Utilizou-se dados primários e secundários, nas análises a regressão Zero-inflado Binomial Negativa, e as variáveis socioeconômicas e ocupacionais nos ajustes. O banco de dados para as análises teve 425 (144 casos; 281 controles) participantes. O baixo suporte do colega aumentou a expectativa de dias de LTS em 2,04 (IC95 por cento: 1,05-3,93), unido ao trabalho de baixa exigência aumentou 2,68 (IC95 por cento: 1,37-5,27) e ao de alta exigência (iso-strain) 78 por cento (IC95 por cento: 1,02-3,12) mais do que o MDC com alto suporte do colega. Este estudo mostrou a importância do suporte do colega sobre a duração absenteísmo-doença, e auxiliou conjeturar que a variável tempo nos trabalhadores de hospital leva a adaptação às exigências das tarefas e a monotonia. Intervenções no relacionamento entre os trabalhadores provavelmente diminuirão a duração de LTS.

The aim of the study was to identify the Job Demand-Control (JDC) and social support contribution for sickness-absenteeism duration of Health Treatment Licences (HTL) in hospital workers (civil servants) of the Santa Catarina State Department of Health of (SES/SC), Brazil. These health workers have the second highest HTL among civil servants in the state, especially those working in hospitals. This is a case-control study nested in a cohort of hospital workers followed up between 07/01/2008 and 06/30/2009. The workers with HTL in this period were selected as cases and those without HTL were selected as cases matched by sex, age and working sector. The outcome was the duration of HTL and the exposure variables were JDC and supervisor and coworker social support. We used both primary and secondary data, zero-inflated negative binomial regression analysis, and socioeconomic and occupation variables in the adjustments. The data used for analysis included 425 participants (144 cases; 281 controls). Low coworker support added 2,04 (95 percent confidence interval (CI): 1,05-3,93) HTL days. This effect increased to 2,68 days (95 percent CI: 1,37-5,27) when combined with low job strain and raised 78 percent (95 percent CI: 1,02-3,12) more than JDC with high coworker support combined with high strain (iso-strain). This study uncovered the importance of coworker support for the duration of sickness-absenteeism and suggested its use for the interventions aiming to decrease the duration of HTL.