Estudios de cohortes especiales / Special cohort studies

Resumen Como se comentó en el artículo anterior (Estudios de cohortes. 1ª parte. Descripción, metodología y aplicaciones), los estudios de cohortes se caracterizan por ser observacionales, longitudinales y analíticos; y en todos ellos se debe considerar una exposición o "factor de exposición", un período de seguimiento, eventuales pérdidas de seguimiento y el desenlace de un resultado. Se han propuesto modificaciones y variantes al diseño del estudio de cohortes tradicional. Se describen de forma resumida, las características principales de los estudios de cohortes con base poblacional, de cohortes bidireccional o ambispectivo; y de otras variantes: según número de cohortes (única y múltiple), de acuerdo al tipo de reclutamiento de la población a estudio (cerrada y abierta), según el tipo de exposición (fija y dinámica); estudio de casos y controles anidado, cohorte-caso; y cohortes ocupacionales (simple con población de referencia externa, simple con grupo de referencia interna y de cohortes múltiples). Finalmente, se desarrollan algunos ejemplos de la literatura de las variantes de cohortes más frecuentes. El objetivo de este manuscrito fue generar un documento de estudio referente a las modificaciones y variantes del diseño del estudio de cohortes.

As we mentioned in a previous article (Cohort studies. 1st part. Description, methodology and applications), cohort studies are characterized by being observational, longitudinal and analytical studies; and in all of them an exposure, a follow-up period, eventual loss of follow-up; and an outcome should be considered. A number of modifications and variants to the traditional cohort study design have been proposed. A summary with the main characteristics of population-based cohort studies, bidirectional cohorts, and of other variants according: to the number of cohorts (single and multiple), to the recruitment of the study population (closed and open), to the exposure (fixed and dynamic); nested case-control study, cohort-case, and occupational cohorts (simple with external reference population, simple with internal reference group and multiple cohorts), are described. Finally, examples of the literature of the most frequent cohort variants are developed. The aim of this manuscript was to generate a study document referring to some of the modifications and variants of cohort studies.

Risk of herpes zoster in patients with systemic lupus erythematosus: a three-year follow-up study using a nationwide population-based cohort

OBJECTIVE: The goal of the present study was to estimate the risk ratio of herpes zoster among systemic lupus erythematosus patients after disease onset compared with a cohort of patients without systemic lupus erythematosus over a three-year period. METHODS: A nationwide population-based cohort study using the National Health Insurance Research Database identified 10,337 new cases of systemic lupus erythematosus as the study cohort. In addition, 62,022 patients without systemic lupus erythematosus, who were matched for age, gender, and date of systemic lupus erythematosus diagnosis, were used as the comparison cohort. These cohorts were followed-up for three years. A Cox proportional hazard regression was performed to estimate the risk ratio of herpes zoster, with adjustments for age, gender, level of insurance, urbanization level, geographic region, comorbid medical conditions, average daily dosage of corticosteroids, and the use of immune-modulation agents. RESULTS: Compared to patients without systemic lupus erythematosus, the crude risk ratio and adjusted risk ratio of herpes zoster among systemic lupus erythematosus patients were 7.37 (95 percent confidence interval 6.75-8.04) and 2.45 (95 percent confidence interval 1.77-3.40), respectively. Stratified by gender, the adjusted risk ratio of herpes zoster was 2.10 (95 percent confidence interval 1.45-2.99) in women and 7.51 (95 percent confidence interval 2.89-19.52) in men. Stratified by age, the adjusted risk ratio peaked in systemic lupus erythematosus patients who were aged 18 to 24 years (risk ratio 8.78, 95 percent confidence interval 3.08-24.97). CONCLUSION: Based on nationwide population-based data, there is an increased risk of herpes zoster in systemic lupus erythematosus patients compared with non-systemic lupus erythematosus patients, particularly among males and patients aged 18 to 24 years. Further research on the associated risk factors for herpes zoster in systemic lupus erythematosus patients is needed.