Trajectories of Late-Life Disability Vary by the Condition Leading to Death

Abstract

Background: Previous research suggested that there might be distinct patterns of functional decline in the last years of life depending on the condition leading to death, but the validity of these results and hence the explanatory value of the condition leading to death for late-life disability are uncertain.

Methods: A total of 636 decedents from a cohort of 754 community-living persons, 70+ years of age (Yale PEP Study) provided 33 700 monthly observations of self-/proxy-reported disability during the last 5 years of life. Nonlinear trajectories and short-term fluctuations of late-life disability by condition leading to death (cancer, organ failure, frailty, severe dementia, sudden death, other) were estimated with flexible mixed spline regression models.

Results: Disability trajectories at the end of life varied distinctively by the condition leading to death. Estimated disability trajectories among cancer deaths increased gradually up until about 6 months before death, after which a steep terminal decline set in. Among those with organ failure, frailty, and dementia, in contrast, disability was higher, increased more gradually, and there was no clear-cut terminal phase. Adding the condition leading to death to other known risk factors increased the amount of explained between-person variation in late-life disability from R2 = 0.35 to 0.49. Short-term fluctuations in disability were not specific for decedents with organ failure.

Conclusions: The condition leading to death is an important determinant of trajectories of late-life disability. These trajectories follow distinct patterns partially resembling a previously outlined theoretical typology.

Keywords: Cause of death; Disability trajectories; End of life; Terminal decline.

Figure 1.

Estimated mean disability trajectories by condition leading to death during the last 5 years. Estimated values are based on the Poisson mixed regression model adjusted for all covariates (sex, race, married, low education, hospital admission, age at death, number of chronic diseases, cognitive impairment, and low social support). For this plot, all effect-coded dichotomous variables were kept constant at value zero, and all continuous variables were kept at mean value. Overall disability refers to the composite index of disability, ADL disability = basic activities of daily living (bathing, dressing, walking inside the house, transferring from a chair), IADL disability = instrumental activities of daily living (shopping, housework, meal preparation, taking medications, managing finances), mobility disability = walking 1/4 mile, climb flight of stairs, lift/carry 10 pounds. Solid lines refer to point estimates, dotted lines refer to 95% credible intervals.