Functional Capacity and Risk for Heart Failure in Older Adults Open Access

Georgiopoulou, Vasiliki (Vicki) (2014)

Permanent URL: https://etd.library.emory.edu/concern/etds/ks65hc45p?locale=en
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Abstract

Functional capacity is associated with several risk factors for heart failure (HF), including cardiovascular disease, elevated blood pressure, and diabetes; and also with mortality. Fit individuals have less risk for cardiovascular disease, hypertension, or diabetes, and lower mortality. Heart failure is an important public health problem with high socioeconomic burden and is significantly associated with age. Therefore, increasing physical activity at the population level might reduce the risk for HF and mortality. Several tests have been used to evaluate functional capacity. Walking tests are the most widely used, because of their simplicity and need of no special equipment or setting. The 6-minute walk test and its variants are widely used for prognostic reasons. However, because of the low ceiling and learning effect of 6-minute walk test, new walking tests have been introduced, especially for special populations. The long distance corridor walk (LDCW) test, introduced in the Health Aging and Body Composition (Health ABC) study, helps older individuals approach their maximum capacity, correlates strongly with oxygen consumption, and carries important prognostic information for mobility limitation and disability, cardiovascular disease, and all-cause mortality in older adults. There are limited data connecting functional capacity and incident HF in middle-aged individuals, and no data are available in older adults who have the highest rates for HF development. Therefore, evaluating the association of functional capacity with HF risk and mortality in older adults using data from well-designed cohort studies is a crucial step to inform the design of interventional studies. In this work, we examine the association between functional capacity, as assessed with the LDCW test, and risk for HF and mortality in older adults. For this purpose, we used 10-year follow-up data from the NIH-funded Health ABC Study, a population-based cohort of 3075 well-functioning, community-dwelling participants aged 70 to 79 years at inception (1997-1998) from Pittsburgh, PA, and Memphis, TN. We evaluated the association between exercise performance and cardiovascular responses recorded during the baseline (year 1) LDCW test and outcomes. Specifically for HF, we considered also the competing risk of mortality using appropriate statistical models. In multivariable models, we adjusted for risk factors previously linked to mortality and incident HF in this cohort along with other parameters linked with reduced functional capacity. Finally, we examined for modification effects of gender, race, and pre-existing cardiovascular disease on the association between functional capacity and 10-year outcomes (mortality and incident HF).

Table of Contents

1. Introduction.............................................................................................................................. 5

1.1 Project Objective................................................................................................................ 5

1.2 The Burden of Heart Failure in Older Adults as a Public Health Problem......................... 5

1.2.1 The Public Health Problem of Heart Failure............................................................... 5

1.2.2 The Role of Aging in Heart Failure.............................................................................. 6

1.2.3 Outcomes and Trends in Patients with Heart Failure................................................. 9

1.3 Study Rationale: Exercise Capacity and Risk for Heart Failure....................................... 10

1.4 Research Questions.......................................................................................................... 13

1.5 Project Assumptions and Contextual Considerations...................................................... 14

2 Literature Review.................................................................................................................... 15

2.1 Functional Capacity and Mortality.................................................................................. 15

2.2 Functional Capacity and Heart Failure............................................................................. 18

2.3 Summary........................................................................................................................... 18

3 Data Collection, Analysis and Results.................................................................................... 20

3.1 Study Design Overview.................................................................................................... 20

3.1.1 Basic Design of Cohort Studies................................................................................. 20

3.1.2 Potential Sources of Bias in Cohort Studies.............................................................. 21

3.1.3 Strengths and Weaknesses of Cohort Studies............................................................ 22

3.2 Measurement of Main Exposure of Interest.................................................................... 23

3.3 Baseline Classification of Disease Status......................................................................... 24

3.4 Surveillance Methods of Event......................................................................................... 25

4 Data Collection, Analysis, and Results:.................................................................................. 25

4.1 Population........................................................................................................................ 25

4.2 Description of the Data Sources....................................................................................... 25

4.3 Identification of the Critical Dependent and Independent Variables................................ 26

4.4 Definition of the Proposed Outcome Measures............................................................... 28

4.4.1 Outcome #1 - Mortality........................................................................................... 28

4.4.2 Outcome #2 - Incident Heart Failure........................................................................ 28

4.5 Analysis Plan.................................................................................................................... 28

4.5.1 Univariate Analyses.................................................................................................. 28

4.5.2 Multivariable Analyses............................................................................................. 29

4.6 Results.............................................................................................................................. 30

4.6.1 Descriptive Statistics................................................................................................. 30

4.6.2 Outcomes................................................................................................................... 34

4.6.3 Association of Exercise and Cardiovascular Responses with Outcomes.................. 36

4.6.4 Association Between Year 4 Exercise Responses and Outcomes............................. 42

5 Journal Article......................................................................................................................... 45

5.1 Introduction...................................................................................................................... 45

5.2 Methods........................................................................................................................... 46

5.2.1 Study Population....................................................................................................... 46

5.2.2 Assessment of Functional Capacity - Long Distance Corridor Walk....................... 47

5.2.3 Study Definitions...................................................................................................... 47

5.2.4 Study Outcomes........................................................................................................ 49

5.2.5 Statistical Analysis.................................................................................................... 49

5.3 Results.............................................................................................................................. 50

5.3.1 Patient Baseline Characteristics................................................................................. 50

5.3.2 Outcomes................................................................................................................... 51

5.3.3 Association of Functional Capacity and Outcomes.................................................. 51

5.3.4 Association Between Year 4 Exercise Responses and Outcomes............................. 53

5.4 Discussion........................................................................................................................ 54

5.5 Tables............................................................................................................................... 55

5.6 Figures.............................................................................................................................. 61

6 Bibliography............................................................................................................................ 63

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