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Longitudinal change in physical functioning and dropout due to death among the oldest old: a comparison of three methods of analysis.

ABSTRACT: Longitudinal studies examining changes in physical functioning with advancing age among very old people are plagued by high death rates, which can lead to biased estimates. This study was conducted to analyse changes in physical functioning among the oldest old with three distinct methods which differ in how they handle dropout due to death. The sample consisted of 3992 persons aged 90 or over in the Vitality 90+ Study who were followed up on average for 2.5 years (range 0–13 years). A generalized estimating equation (GEE) with independent ‘working’ correlation, a linear mixed-effects (LME) model and a joint model consisting of longitudinal and survival submodels were used to estimate the effect of age on physical functioning over 13 years of follow-up. We observed significant age-related decline in physical functioning, which furthermore accelerated significantly with age. The average rate of decline differed markedly between the models: the GEE-based estimate for linear decline among survivors was about one-third of the average individual decline in the joint model and half the decline indicated by the LME model. In conclusion, the three methods yield substantially different views on decline in physical functioning: the GEE model may be useful for considering the effect of intervention measures on the outcome among living people, whereas the LME model is biased regarding studying outcomes associated with death. The joint model may be valuable for predicting the future characteristics of the oldest old and planning elderly care as life expectancy continues gradually to rise.

SUBMITTER: Raitanen J

PROVIDER: S-EPMC7292844 | biostudies-literature | 2020 Jun

REPOSITORIES: biostudies-literature

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Project description:BackgroundThe oldest-old (those aged ≥80 years) are the most rapidly growing age group globally, and are most in need of health care and assistance. We aimed to assess changes in mortality, disability in activities of daily living, and physical and cognitive functioning among oldest-old individuals between 1998 and 2008.MethodsWe used data from the Chinese Longitudinal Healthy Longevity Study. Three pairs of cohorts aged 80-89 years, 90-99 years, and 100-105 years (in total, 19 528 oldest-old participants) were examined; the two cohorts in each pair were born 10 years apart, with the same age at the time of the assessment in the 1998 and 2008 surveys. Four health outcomes were investigated: annual death rate, Activities of Daily Living (ADL), physical performance in three tests and cognitive function measured by Mini-Mental State Examination (MMSE). We used different tests and multivariate regression analyses to examine the cohort differences.FindingsControlling for various confounding factors, we noted that annual mortality among oldest-old individuals was substantially reduced between 0·2% and 1·3% in 1998-2008 compared with individuals of the same age born 10 years previously, and that disability according to activities of daily living had significantly reduced annually between 0·8% and 2·8%. However, cognitive impairment in the later cohorts increased annually between 0·7% and 2·2% and objective physical performance capacity (standing up from a chair, picking up a book from the floor, and turning around 360°) decreased anually between 0·4% and 3·8%. We also noted that female mortality was substantially lower than male mortality among the oldest-old, but that women's functional capacities in activities of daily living, cognition, and physical performance were worse than their male counterparts.InterpretationAdvances in medications, lifestyle, and socioeconomics might compress activities of daily living disability, that is, benefits of success, but lifespan extension might expand disability of physical and cognitive functioning as more frail, elderly individuals survive with health problems, that is, costs of success.FundingNational Natural Science Foundation of China, National Institute on Aging/National Institutes of Health, United Nations Funds for Population Activities.

Project description:BackgroundThe ability to accurately predict survival in older adults is crucial as it guides clinical decision making. The added value of using various health indicators as well as changes in these indicators for predicting mortality remains unclear. The aim of this study was to investigate whether changes in health indicators such as frailty and physical performance improve mortality predictions in old age.MethodsThis is a population based prospective cohort study on 995 community-dwelling people aged 68-92 years from the Longitudinal Aging Study Amsterdam. Two measurements at a three-year interval (1995/1996 and 1998/1999) were available for the frailty index, frailty phenotype, grip strength, walking speed, and Mini-Mental State Examination (MMSE). Cox regression was used to analyze mortality risks associated with the current health status and changes in health, with mortality data up to 2017. The extent to which these health indicators improved mortality predictions compared to models with age and sex only was assessed by the area under the receiver operating characteristic curve (AUC).ResultsThe AUC of age and sex for five-year mortality was 72.8% (95% CI 69.0 - 76.5) and was the lowest in the oldest old (age > 80.5 years). The added AUC of the current status of health indicators ranged from 0.7 to 3.3%. The added AUC of the three-year change was lower, ranging from -0.0 to 1.1%, whereas the added AUC of three-year change and current status combined was similar to current status alone, ranging from 0.6 to 3.2%. Across age, the added AUC of current status was highest in the oldest old, however there was no such pattern using three-year change. Overall, the frailty index appeared to improve mortality predictions the most, followed by the frailty phenotype, MMSE, grip strength, and walking speed.ConclusionsCurrent health status improved mortality predictions better than changes in health. Its contribution was highest in the oldest old, but the added value to models with age and sex only was limited.

Project description:IntroductionSeveral studies have suggested that physical activity and sedentary behavior are strongly and independently associated with body composition and obesity. However, few studies have investigated whether substituting sedentary time with moderate-to-vigorous physical activity is associated with body composition in older adults, especially among those older than 75 years.MethodsThis study examined the associations between replacing sedentary time with physical activity and obesity indices in a sample of 199 community-dwelling older Taiwanese adults (52.3% women; 80.6 ± 7.0 years). Physical activity and sedentary behavior were measured using the triaxial accelerometer (GT3X+, ActiGraph). Body composition indices were computed through a bioelectrical impedance analysis of body fat percentage and appendicular skeletal muscle mass index. Waist circumference and body mass index were measured by trained personnel. Isotemporal substitution analyses estimated these associations after adjusting for sociodemographic characteristics and nutritional status.ResultsThe study showed that substituting 30 min of sedentary behavior per day with moderate-to-vigorous physical activity was associated with lower body fat percentage (B = -1.408, 95% CI = -2.55, -0.264), body mass index (B = -0.681, 95% CI = -1.300, -0.061), and waist circumference (B = -2.301, 95% CI = -4.062, -0.539) after adjusting for covariates. Substituting 30 min of light physical activity per day with moderate-to-vigorous physical activity was associated with lower waist circumference (B = -2.230, 95% CI = -4.173, -0.287) after adjusting for covariates. Stratified analyses indicated that associations were stronger in youngest-old older adults, and in older adults with a normal nutritional status (vs. underweight status).DiscussionThese findings confirm the importance of reducing sedentary behavior and increasing moderate-to-vigorous physical activity among older adults to improve their physical health, as well as highlighting the importance of taking into account nutritional status and age group.

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Longitudinal change in physical functioning and dropout due to death among the oldest old: a comparison of three methods of analysis.

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