Dietary Sodium Content, Mortality, and Risk for Cardiovascular Events in Older Adults Open Access

Kalogeropoulos, Andreas (2013)

Permanent URL: https://etd.library.emory.edu/concern/etds/hq37vp052?locale=en
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Abstract

Excess dietary sodium intake is associated with risk factors for cardiovascular disease (CVD) and heart failure (HF), mainly elevated blood pressure and adverse vascular effects. Therefore, limiting sodium intake at the population level might reduce risk for CVD and HF. However, the optimal level of sodium restriction is currently unclear. Although simulation studies have projected significant benefits with strict sodium control, low sodium intake may exert unfavorable effects on certain factors predisposing to CVD and HF. Recently published findings from large cohorts have disputed the current recommendations (≤2300 mg daily for the general population, ≤1500 mg for high risk groups, including older adults). Specifically for older adults, concerns with strict sodium control include inadequate caloric intake and interaction with medications. For example, experimental evidence suggests that combining renin-angiotensin system blockade with low sodium impairs cardio-myocyte contractility. Moreover, dose-response data on sodium intake and outcomes are scarce in older adults. Therefore, evaluating the association of dietary sodium with key outcomes in older adults using data from well-designed cohort studies is a crucial step to inform design of much needed outcome trials. In this work, we examine the association between sodium intake, as assessed with a food frequency questionnaire, and risk for mortality, CVD, and HF in older adults. For this purpose, we evaluated 10-year follow-up data from the NIH-funded Health, Aging, and Body Composition (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 functional form of association (linear vs. nonlinear) between sodium intake and outcomes and considered the competing risk of non-cardiovascular mortality for incident CVD and HF using appropriate statistical models. In multivariable models, we adjusted for risk factors previously linked to mortality and incident CVD and HF in this cohort. Finally, we examined for modification effects of gender, race, and baseline hypertensive status on the association between dietary sodium intake and 10-year cardiovascular outcomes.

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

Heart Failure as Public Health Problem................................................................................... 5 Aging and Heart Failure........................................................................................................... 6 Contemporary Outcomes and Trends in Patients with Heart Failure..................................... 8

1.3. Study Rationale: The Conundrum of Dietary Sodium Intake and Risk for Cardiovascular Disease and Heart Failure 9

1.4. Research Questions......................................................................................................... 11 1.5. Project Assumptions and Contextual Considerations..................................................... 12

2. Literature Review................................................................................................................... 13

2.1. Dietary Sodium Intake and Mortality............................................................................. 13 2.2. Dietary Sodium Intake and Cardiovascular Disease........................................................ 15 2.3. Dietary Sodium Intake and Heart Failure........................................................................ 17 2.4. Summary.......................................................................................................................... 17

3. Design and Methodology....................................................................................................... 18

3.1. Study Design Overview................................................................................................... 18 Basic Design of Cohort Studies............................................................................................. 18 Potential Sources of Bias in Cohort Studies.......................................................................... 18 Strengths and Weaknesses of Cohort Studies........................................................................ 19 3.2. Measurement of Main Exposure of Interest................................................................... 20 3.3. Baseline Disease Status Classification............................................................................. 21 3.4. Event Surveillance Methods............................................................................................ 21

4. Data Collection, Analysis, and Results:................................................................................. 21

4.1. Description of the Data Sources...................................................................................... 21

4.2. Identification of the Critical Dependent and Independent Variables............................... 22

4.3. Definition of the Proposed Outcome Measures.............................................................. 23 Outcome #1 - Mortality....................................................................................................... 23 Outcome #2 - Incident Cardiovascular Disease.................................................................... 23 Outcome #3 - Incident Heart Failure.................................................................................... 23 4.4. Analysis Plan................................................................................................................... 24 Descriptive Statistics............................................................................................................. 24 Inferential Statistics............................................................................................................... 25 4.5. Results............................................................................................................................. 26 Descriptive Statistics............................................................................................................. 26 Outcomes............................................................................................................................... 28 Univariate Association of Sodium Intake with Outcomes.................................................... 28 Multivariable Association of Sodium Intake with Outcomes............................................... 36

5. Journal Article........................................................................................................................ 46

5.1. Introduction..................................................................................................................... 46 5.2. Methods.......................................................................................................................... 47 Study Population................................................................................................................... 47 Assessment of Dietary Sodium Intake.................................................................................. 48 Study Definitions.................................................................................................................. 48 Study Outcomes.................................................................................................................... 49 Statistical Analysis................................................................................................................ 49 5.3. Results............................................................................................................................. 50 Baseline Characteristics......................................................................................................... 50 Outcomes............................................................................................................................... 50 Sodium Intake and Outcomes................................................................................................ 50 5.4. Discussion....................................................................................................................... 52 5.5. Tables.............................................................................................................................. 55 5.6. Figures............................................................................................................................. 60 6. Bibliography........................................................................................................................... 63

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