Surrogate screening models for the low physical activity criterion of frailty
Sandrah P. Eckel1, Karen Bandeen-Roche2,3, Paulo H.M. Chaves3,4, Linda P. Fried5 and Thomas A. Louis2
1Division of Biostatistics, Keck School of Medicine, University of Southern California, Los Angeles, California, 2Department of Biostatistics, The Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, 3Center on Aging and Health and 4Division of Geriatric Medicine and Gerontology, Department of Medicine, The Johns Hopkins Medical Institutions, Baltimore, Maryland, 5Mailman School of Public Health, Columbia University, New York, New York, USA

Abstract

Background and aims: Low physical activity, one of five criteria in a validated clinical phenotype of frailty, is assessed by a standardized, semiquantitative questionnaire on up to 20 leisure time activities. Because of the time demanded to collect the interview data, it has been challenging to translate to studies other than the Cardiovascular Health Study (CHS), for which it was developed. Considering subsets of activities, we identified and evaluated streamlined surrogate assessment methods and compared them to one implemented in the Women’s Health and Aging Study (WHAS). Methods: Using data on men and women ages 65 and older from the CHS, we applied logistic regression models to rank activities by “relative influence” in predicting low physical activity. We considered subsets of the most influential activities as inputs to potential surrogate models (logistic regressions). We evaluated predictive accuracy and predictive validity using the area under receiver operating characteristic curves and assessed criterion validity using proportional hazards models relating frailty status (defined using the surrogate) to mortality. Results: Walking for exercise and moderately strenuous household chores were highly influential for both genders. Women required fewer activities than men for accurate classification. The WHAS model (8 CHS activities) was an effective surrogate, but a surrogate using 6 activities (walking, chores, gardening, general exercise, mowing and golfing) was also highly predictive. Conclusions: We recommend a 6 activity questionnaire to assess physical activity for men and women. If efficiency is essential and the study involves only women, fewer activities can be included. (Aging Clin Exp Res 2011; 23: 209-216) ©2011, Editrice Kurtis

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