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Medical Biomathematics and Biometrics Commons™
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Articles 1 - 7 of 7
Full-Text Articles in Medical Biomathematics and Biometrics
The Number Of Sick Persons In A Cohort, Paula Diehr
The Number Of Sick Persons In A Cohort, Paula Diehr
Paula Diehr
To see if the number of sick persons in a cohort was approximately constant over time, we calculated the number of sick persons in a “research” cohort of older adults followed for up to 14 years, and also in a synthetic birth cohort. Methods: In the research cohort, we calculated the actual number of persons in each health state over time, using eight different definitions of “sick”. For the birth cohort, we estimated the number of sick persons each year after birth. Results: The number of sick persons in the research cohort was approximately constant for 14 years, for all …
Accounting For Missing Data In End-Of-Life Research, Paula Diehr, Laura Lee Johnson
Accounting For Missing Data In End-Of-Life Research, Paula Diehr, Laura Lee Johnson
Paula Diehr
End-of-life studies are likely to have missing data because sicker persons are less likely to provide information and because measurements cannot be made after death. Ignoring missing data may result in data that are too favorable, because the sickest persons are effectively dropped from the analysis. In a comparison of two groups, the group with the most deaths and missing data will tend to have the most favorable data, which is not desirable. Results based on only the available data may not be generalizable to the original study population. If most of the missing data are absent because of death, …
Methods For Incorporating Death Into Health-Related Variables In Longitudinal Studies, Paula Diehr
Methods For Incorporating Death Into Health-Related Variables In Longitudinal Studies, Paula Diehr
Paula Diehr
BACKGROUND AND OBJECTIVES: Longitudinal studies of health over time may be misleading if some people die. Self-rated health (excellent to poor) and the SF-36 profile scores have been transformed to incorporate death. We applied the same approaches to incorporate death into activities of daily living difficulties (ADLs), IADLs, mini-mental state examination, depressive symptoms, blocks walked per week, bed days, the timed walk, body mass index and blood pressure. STUDY DESIGN AND SETTING: The Cardiovascular Health Study of 5,888 older adults, was followed up to 9 years. Mean age was 73 at baseline, and 658 had an incident stroke during follow-up. …
Trajectories Of Health For Older Adults Over Time: Accounting Fully For Death, Paula Diehr
Trajectories Of Health For Older Adults Over Time: Accounting Fully For Death, Paula Diehr
Paula Diehr
The process of healthy aging can best be described by plotting the trajectory of health-related variables over time. Unfortunately, graphs including data only from survivors may be misleading because they may confuse patterns of mortality with patterns of change in health. Two approaches for creating graphs that account for death in such situations are 1) to incorporate a category or value for death into the longitudinal health variable and 2) to measure time in years before death or some other event. The first approach has been applied to self-rated health (excellent to poor) and the 36-Item Short-Form Health Survey (SF-36). …
The Aging And Dying Processes And The Health Of Older Adults, Paula Diehr
The Aging And Dying Processes And The Health Of Older Adults, Paula Diehr
Paula Diehr
It is difficult to distinguish changes in health due to aging from those related to dying, because the two processes are highly related. Some potentially treatable conditions may mistakenly be dismissed as due to old age. The goal of this article was to examine the relationships of aging and of dying to changes in 10 health-related variables: self-rated health, depression, ADLs, IADLs, minimental state examination, body mass index, blocks walked per week, bed days, hospitalization, and walking speed (all coded so that higher values were better). We used longitudinal data from the Cardiovascular Health Study to estimate the changes in …
Transforming Self-Rated Health And The Sf-36 Scales To Include Death And Improve Interpretability, Paula Diehr
Transforming Self-Rated Health And The Sf-36 Scales To Include Death And Improve Interpretability, Paula Diehr
Paula Diehr
BACKGROUND: Most measures of health-related quality of life are undefined for people who die. Longitudinal analyses are often limited to a healthier cohort (survivors) that cannot be identified prospectively, and that may have had little change in health. OBJECTIVE: To develop and evaluate methods to transform a single self-rated health item (excellent to poor; EVGGFP) and the physical component score of the SF-36 (PCS) to new variables that include a defensible value for death. METHODS: Using longitudinal data from two large studies of older adults, health variables were transformed to the probability of being healthy in the future, conditional on …
Including Deaths When Measuring Health Status Over Time, Paula Diehr
Including Deaths When Measuring Health Status Over Time, Paula Diehr
Paula Diehr
Measuring health status over time is problematic when some subjects die, because death does not have a defined value on most health status measures. This situation is different from the usual missing data problem because the health status of the dead is, in a sense, known. We examined eight strategies for incorporating deaths into such analyses using three health status measures taken from two data sets, after which we used computer simulation to explore more fully the effect of deaths. The strategies differed in the amount of influence given to the deaths, varying from none (deaths were discarded) to complete …