title: Incident disability in older adults: prediction models based on two British prospective cohort studies.
abstract: OBJECTIVE
  To develop and validate a prediction model for incident locomotor disability after 7 years in older adults.
  
  
  METHODS
  Prospective British cohort studies: British Women's Heart and Health Study (BWHHS) for development and the English Longitudinal Study of Ageing (ELSA) for validation.
  
  
  METHODS
  Community-dwelling older adults.
  
  
  METHODS
  Multivariable logistic regression models after selection of predictors with backward elimination. Model performance was assessed using metrics of discrimination and calibration. Models were internally and externally validated.
  
  
  RESULTS
  Locomotor disability was reported in BWHHS by 861 of 1,786 (48%) women after 7 years. Age, a history of arthritis and low physical activity levels were the most important predictors of locomotor disability. Models using routine measures as predictors had satisfactory calibration and discrimination (c-index 0.73). Addition of 31 blood markers did not increase the predictive performance. External validation in ELSA showed reduced discrimination (c-index 0.65) and an underestimation of disability risks. A web-based calculator for locomotor disability is available (http://www.sealedenvelope.com/trials/bwhhsmodel/).
  
  
  CONCLUSIONS
  We developed and externally validated a prediction model for incident locomotor disability in older adults based on routine measures available to general practitioners, patients and public health workers, and showed an adequate discrimination. Addition of blood markers from major biological pathways did not improve the performance of the model. Further replication in additional data sets may lead to further enhancement of the current model.
authors.affiliation: Faculty of Epidemiology and Population Health, London School of Hygiene and Tropical Medicine, London, UK.
authors.forename: Eveline
authors.initials: E
authors.lastname: Nüesch
authors.affiliation: Faculty of Epidemiology and Population Health, London School of Hygiene and Tropical Medicine, London, UK.
authors.forename: Perel
authors.initials: P
authors.lastname: Pablo
authors.affiliation: Faculty of Epidemiology and Population Health, London School of Hygiene and Tropical Medicine, London, UK.
authors.forename: Caroline E
authors.initials: CE
authors.lastname: Dale
authors.affiliation: Faculty of Epidemiology and Population Health, London School of Hygiene and Tropical Medicine, London, UK.
authors.forename: David
authors.initials: D
authors.lastname: Prieto-Merino
authors.affiliation: Institute of Epidemiology and Health, University College London, London, UK.
authors.forename: Meena
authors.initials: M
authors.lastname: Kumari
authors.affiliation: Faculty of Health Sciences, University of Southampton, Southampton, UK.
authors.forename: Ann
authors.initials: A
authors.lastname: Bowling
authors.affiliation: Faculty of Epidemiology and Population Health, London School of Hygiene and Tropical Medicine, London, UK.
authors.forename: Shah
authors.initials: S
authors.lastname: Ebrahim
authors.affiliation: Faculty of Epidemiology and Population Health, London School of Hygiene and Tropical Medicine, London, UK Institute of Epidemiology and Health, University College London, London, UK.
authors.forename: Juan P
authors.initials: JP
authors.lastname: Casas
mesh_terms: D000203:Activities of Daily Living; D000367:Age Factors; D000368:Aged; D001168:Arthritis / Q000453:epidemiology; D003661:Decision Support Techniques; D004185:Disability Evaluation; D006233:Persons with Disabilities / Q000706:statistics & numerical data*; D005260:Female; D015577:Geriatric Assessment; D006801:Humans; D015994:Incidence; D016015:Logistic Models; D008297:Male; D009043:Motor Activity; D015999:Multivariate Analysis; D016017:Odds Ratio; D011237:Predictive Value of Tests; D011446:Prospective Studies; D015203:Reproducibility of Results; D012307:Risk Factors; D057185:Sedentary Behavior; D013997:Time Factors; D006113:United Kingdom
keywords: aged; clinical prediction rule; locomotor disability; older people