Luis Rosero Bixby
Permanent URI for this collectionhttps://repositorio.sibdi.ucr.ac.cr/handle/123456789/16105
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Item Self-reported versus performance-based measures of physical function: prognostic value for survival(Demographic Research; Volumen 30, Número 7, 2014) Glei, Dana; Rosero Bixby, Luis; Chiou, Shu-Ti; Weinstein, Maxine; Goldman, NoreenBackground: Although previous studies have indicated that performance assessments strongly predict future survival, few have evaluated the incremental value in the presence of controls for self-reprted activity and mobility limitations. Objective: We assess and compare the added value of four tests -- walking speed, chair stands, grip strength, and peak expiratory flow (PEF) -- for predicting all-cause mortality. Methods: Using population-based samples of older adults in Costa Rica (n = 2290, aged 60+) and Taiwan (n = 1219, aged 53+), we estimate proportional hazards models of mortality for an approximate five-year period. Receiver Operator Characteristic (ROC) curves are used to assess the prognostic value of each performance assessment. Results: Self-reprted measures of physical limitations contribute substantial gains in mortality prediction, whereas performance-based assessments yield modest incremental gains. PEF provides the greatest added value, followed by grip strength. Our results suggest that including more than two performance assessments may provide little improvement in mortality prediction. Conclusions: PEF and grip strength are often simpler to administer in home interview settings, impose less of a burden on some respondents, and, in the presence of self-reprted limitations, appear to be better predictors of mortality than do walking speed or chair stands. Comments: Being unable to perform the test is often a strong predictor of mortality, but these indicators are not well-defined. Exclusion rates vary by the specific task and are likely to depend on the underlying demographic, health, social and cultural characteristics of the sample.Item Disease and weight loss: a prospective study of middle-aged and older adults in Costa Rica and England(Salud Pública de México; Volumen 57, Número 4, 2015) Blue, Laura; Rosero Bixby, Luis; Goldman, NoreenObjective. To determine whether disease predicts weight loss in population-based studies, as this may confound the relationship between weight and mortality. Materials and methods. We used longitudinal data from the Costa Rican Longevity and Healthy Aging Study (CRELES) and the English Longitudinal Study of Ageing (ELSA). We defined two overlapping outcomes of measured weight loss between waves: >1.0 point of body mass index (BMI) and >2.0 BMI points. Logistic regression models estimated the associations with disease, adjusting for age (range 52-79), sex, smoking, and initial BMI. Results. In ELSA, onset of diabetes, cancer, or lung disease is associated with loss >2.0 points (respectively, OR=2.25 [95%CI: 1.34-3.80]; OR=2.70 [95%CI: 1.49-4.89]; OR=1.82 [95%CI: 1.02-3.26]). In CRELES, disease-onset reprts are not associated with weight loss at 5% significance, but statistical power to detect associations is poor. Conclusion. Although it is known that some diseases cause weight loss, at the population level these associations vary considerably across samples. Objetivo. Determinar si las enfermedades predicen pérdida de peso a partir de encuestas poblacionales, debido a que esto podría confundir la relación entre peso y mortalidad. Material y métodos. Se utilizaron datos longitudinales de Costa Rica: Estudio de Longevidad y Envejecimiento Saludable (CRELES) y Estudio Longitudinal de Envejecimiento en Inglaterra (ELSA, por sus siglas en inglés). Se definieron dos indicadores de resultado no excluyentes de pérdida de peso entre rondas: >1.0 punto de índice de masa corporal (IMC) y >2.0 puntos de IMC. Las asociaciones de interés se estimaron con modelos de regresión logística, con controles para la edad (rango 52-79), sexo, tabaquismo actual e IMC inicial. Resultados. En el ELSA, la incidencia de diabetes, cáncer o enfermedad pulmonar está asociada con pérdida de >2.0 puntos de IMC (respectivamente: OR=2.25 [IC95%: 1.34-3.80]; OR=2.70 [IC95%: 1.49-4.89]; OR=1.82 [IC95%: 1.02-3.26]). En el CRELES, el reprte de diagnóstico de enfermedades no muestra asociación significativa a 5% con pérdida de peso, pero el poder estadístico de la muestra para detectar asociaciones es limitado. Conclusión. Aunque es conocido que ciertas enfermedades causan pérdida de peso, estas asociaciones a nivel poblacional varían considerablemente entre encuestas.