title: Long-term trajectories of lower extremity function in older adults: estimating gender differences while accounting for potential mortality bias.
abstract: BACKGROUND
  Gender-specific trajectories of lower extremity function (LEF) and the potential for bias in LEF estimation due to differences in survival have been understudied.
  
  
  METHODS
  We evaluated longitudinal data from 690 initially nondisabled adults age 70 or older from the Precipitating Events Project. LEF was assessed every 18 months for 12 years using a modified Short Physical Performance Battery (mSPPB). Hierarchical linear models with adjustments for length-of-survival estimated the intraindividual trajectory of LEF and differences in trajectory intercept and slope between men and women.
  
  
  RESULTS
  LEF declined following a nonlinear trajectory. In the full sample, and among participants with high (mSPPB 10-12) and intermediate (mSPPB 7-9) baseline LEF, the rate-of-decline in mSPPB was slower in women than in men, with no gender differences in baseline mSPPB scores. Among participants with low baseline LEF (mSPPB ≤6), men had a higher starting mSPPB score, whereas women experienced a deceleration in the rate-of-decline over time. In all groups, participants who survived longer had higher starting mSPPB scores and slower rates-of-decline compared with those who died sooner.
  
  
  CONCLUSIONS
  Over the course of 12 years, older women preserve LEF better than men. Nonadjustment for differences in survival results in overestimating the level and underestimating the rate-of-decline in LEF over time.
authors.affiliation: Yale University, Department of Internal Medicine/Geriatrics, 20 York Street, New Haven, Connecticut, USA. anda.botoseneanu@yale.edu
authors.forename: Anda
authors.initials: A
authors.lastname: Botoseneanu
authors.forename: Heather G
authors.initials: HG
authors.lastname: Allore
authors.forename: Evelyne A
authors.initials: EA
authors.lastname: Gahbauer
authors.forename: Thomas M
authors.initials: TM
authors.lastname: Gill
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000375:Aging; D015982:Bias; D003237:Connecticut / Q000453:epidemiology; D006233:Persons with Disabilities / Q000706:statistics & numerical data*; D005260:Female; D015577:Geriatric Assessment; D006801:Humans; D008137:Longitudinal Studies; D035002:Lower Extremity; D008297:Male; D009026:Mortality; D053580:Muscle Strength; D012307:Risk Factors; D017678:Sex Distribution; D012737:Sex Factors; D013997:Time Factors