Estimates of active and disabled life expectancy based on different assessment intervals

J Gerontol A Biol Sci Med Sci. 2005 Aug;60(8):1013-6. doi: 10.1093/gerona/60.8.1013.


Background: Although disability in activities of daily living (ADLs) is a highly dynamic process, analytic strategies for estimating active and disabled life expectancy have assumed stability in ADL function between periodic surveys spanning 12--24 months or have used interval estimation or instantaneous rates based on long assessment intervals. We performed a prospective cohort study to compare estimates of active and disabled life expectancy based on traditional assessment intervals of 1--2 years with those based on more frequent assessments at 1-month intervals.

Methods: Participants included 754 initially nondisabled community-dwelling persons, aged 70 years or older, who were interviewed monthly for 4 years to ascertain ADL disability. Estimates of active and disabled life expectancy were calculated using an increment-decrement life table for assessment intervals of 1 month, 1 year, and 2 years.

Results: For each of five age groups, the monthly assessment strategy yielded the highest values for active life expectancy and the lowest values for disabled life expectancy. The 95% confidence intervals for these values, however, overlapped the corresponding point estimates for the annual and biennial strategies.

Conclusions: Accurate estimates of active and disabled life expectancy may be obtained from epidemiologic studies that assess ADL function no more frequently than every other year.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Activities of Daily Living
  • Age Factors
  • Aged
  • Aged, 80 and over
  • Aging
  • Cohort Studies
  • Disabled Persons
  • Female
  • Humans
  • Life Expectancy*
  • Life Tables
  • Longitudinal Studies
  • Male
  • Prospective Studies
  • Time Factors