Obesity, health status, and 7-year mortality in percutaneous coronary intervention: In search of an explanation for the obesity paradox

doi:10.1016/j.ijcard.2012.03.105

International Journal of Cardiology

Volume 167, Issue 4, 20 August 2013, Pages 1154-1158

https://doi.org/10.1016/j.ijcard.2012.03.105 Get rights and content

Abstract

Background

Obesity is a growing health problem and is associated with adverse outcomes in coronary artery disease (CAD). However, recent studies have shown better survival in cardiovascular patients with overweight or obesity, which has been referred to as the “obesity paradox”. As there is no clear understanding of the phenomenon, we examined the association between body mass index (BMI) and all-cause mortality in patients treated with percutaneous coronary intervention (PCI) at 7-year follow-up, and the potential role of health status in explaining the obesity paradox.

Methods

Consecutive PCI patients (72.5% men; mean age 62.0 ± 11.2 years, range [27–90] years) from the Rapamycin-Eluting Stent Evaluated at Rotterdam Cardiology Hospital (RESEARCH) registry completed the 36-item short-form health survey (SF-36) to assess health status at baseline. Patients were classified into a normal weight, overweight or obesity group.

Results

The prevalence of normal weight was 34.7% (354/1019), overweight was seen in 45.9% (468/1019) of patients, and 19.3% (197/1019) was obese. After a median follow-up of 7.0 ± 1.7 years, 163 deaths (16.0%) from any cause were recorded. Cumulative hazard functions differed significantly for the obese and overweight group when compared to the normal weight group (log-rank X² = 6.59, p < 0.05). In multivariable analysis, overweight, but not obesity, remained associated with a lower risk for all-cause mortality (HR = 0.60, 95%CI [0.42–0.86], p = 0.005). Additionally, after adding the 8 health status SF-36 domains to the multivariate model, the association between overweight and mortality remained unchanged.

Conclusion

In our study population overweight, but not obesity, was associated with a lower risk for 7-year mortality in PCI patients. Health status as measured with the SF-36 did not seem to play a role in explaining the obesity paradox.

Introduction

Obesity is a growing epidemic, with prevalence rates in the general population ranging from 32% in men to 36% in women [1]. In coronary artery disease (CAD), obesity is prevalent in 29% of patients [2] and is associated with potential risk for cardiovascular morbidity and mortality [3], [4]. However, evidence for a link between obesity and cardiovascular prognosis is based on a small number of studies, with results being mixed, as some [5] but not all studies support such a relationship [6]. Moreover, recent studies have demonstrated that there may not be a linear and straightforward relationship between overweight and obesity and mortality, as some studies show better survival in cardiovascular patients with overweight or obesity. This phenomenon is referred to as the “obesity paradox” [6], [7], [8], [9].

In an attempt to explain the obesity paradox, studies have primarily focused on potential differences in the prescription of guideline-based medications [2], [7]. A higher prevalence of invasive treatment has also been observed in obese patients with CAD [2]. Nevertheless, we still do not have a clear understanding of the obesity paradox.

Patient-reported health status might be another avenue to pursue in order to elucidate factors that may impinge on or help explain the obesity paradox. A recent systematic review demonstrated that poor health status in CAD and congestive heart failure increase the risk of mortality and hospital readmissions independent of indicators of disease severity and demographic and clinical characteristics [10]. Also a recent paper from our research group found an association between poor health status and higher mortality [11]. A paucity of studies focused on the association between obesity and health status [12], [13], [14], [15], but the role of health status in the context of obesity and mortality in CAD has not yet been examined.

Hence, in the current study we examined 1) the association between BMI and all-cause mortality in patients treated with percutaneous coronary intervention (PCI) at 7-year follow-up, and 2) the potential role of health status in explaining the obesity paradox.

Section snippets

Study population

The study sample comprised consecutive CAD patients treated with PCI with either sirolimus-eluting stenting (SES) or bare metal stenting (BMS), between October 16, 2001 and October 15, 2002 at the Erasmus Medical Center, Rotterdam, The Netherlands, as part of the Rapamycin-Eluting Stent Evaluated at Rotterdam Cardiology Hospital (RESEARCH) registry. The design of the RESEARCH registry has been published elsewhere [16]. In brief, the registry was designed to evaluate the efficacy and safety of

Statistical analyses

Prior to statistical analyses, we dichotomized all 8 health status domains, as suggested by others, in order to enhance clinical interpretability [22], [23]. The lowest tertile was used to indicate poor health status and the 2 highest tertiles to indicate good health status. Categorization of BMI was adopted from the World Health Organization and defined as normal weight: 18.5 to 24.99 kg/m², overweight: 25 to 29.99 kg/m², and obese: ≥ 30 kg/m² [24], [25]. For all analyses, normal weight was used

Patient characteristics

Of 1675 eligible patients treated with PCI in the study period, 54 patients died within 6 months. Of the remaining 1621 patients asked to participate in the study, 602 did not return the questionnaire at baseline (62.9% response rate). Final analyses were based on data from 1019 patients (72.5% men; mean age 62.0 ± 11.2 years, range [27–90] years). No systematic differences between participants and non participants were found on baseline characteristics, except for non participants more often having

Discussion

To our knowledge, this is the first study which examined whether the paradoxical association between BMI, mortality, could be explained by health status. After a median follow-up of 7 years, overweight, but not obesity, was associated with a lower risk for all-cause mortality in patients treated with PCI, after adjusting for socio-demographic and clinical characteristics. We found no evidence that health status played a role in explaining the obesity paradox.

The results of the current study are

Limitations

Limitations of the current study must be acknowledged. First, data on abdominal obesity, measured by waist circumference and waist/hip ratio, were not available. A recent meta-analysis showed that central obesity was associated with higher mortality in CAD, whereas total obesity (BMI) was not [46]. Therefore, future research should focus on the different aspects of obesity, rather than total obesity alone. Second, the SF-36 is a generic measure of health status, which may be less sensitive to

Conclusion

The current study showed that after a median follow-up of 7 years, overweight, but not obesity, was associated with lower mortality. In the current study, health status did not seem to play a role in explaining the obesity paradox.

Acknowledgments

The authors of the manuscript have certified that they comply with the principles of ethical publishing in the International Journal of Cardiology.

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Citation Excerpt :
When reviewing the “protective” effects of obesity in the cardiology literature, one study found that lean patients had worse underlying non-cardiovascular diseases compared to their obese counterparts.23 Another study examined the quality of health at baseline using the 36-item short-form health survey (SF-36) and found no difference between obese and non-obese patients.24 When examining the comorbidities of trauma patients in this study, we found that patients who were overweight or Class 1 obese had lower incidences of chronic obstructive pulmonary disease (COPD) and major psychiatric illnesses.
There are limited studies examining the role of BMI on mortality in the trauma population. The aim of this study was to analyze whether the “obesity paradox” exists in non-elderly patients with blunt trauma.
A retrospective study was performed on the Trauma Quality Improvement Program (TQIP) database for 2016. All non-elderly patients aged 18–64, with blunt traumatic injuries were identified. A generalized additive model (GAM) was built to assess the association of mortality and BMI adjusted for age, gender, race, and injury severity score (ISS).
28,475 patients (mean age = 42.5, SD = 14.3) were identified. 20,328 (71.4%) were male. Age (p < 0.0001), gender (p < 0.0001), and ISS (p < 0.0001) had significant associations with mortality. After GAM, BMI showed a significant U-shaped association with mortality (EDF = 3.2, p = 0.003). A BMI range of 31.5 ± 0.9 kg/m² was associated with the lowest mortality.
High BMI can be a protective factor in mortality within non-elderly patients with blunt trauma. However, underweight or morbid obesity suggest a higher risk of mortality.
The Association of Body Mass Index and 20-Year All-Cause Mortality Among Patients With Stable Coronary Artery Disease
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Most of these studies focussed on patients admitted with an acute coronary syndrome or those undergoing percutaneous coronary intervention (PCI) [8–11,14–16] or had a relatively short follow-up period. [7–9,11,14] Other studies, including mainly patients after PCI, have shown that the association of higher BMI with lower mortality risk was diminished, thus contradicting the “Obesity Paradox” phenomenon.[17–20] Thus, there is limited and contradictory data regarding the very long-term association of BMI and all-cause mortality among patients with stable CAD.
Limited data exist regarding the long-term association of body mass index (BMI) and all-cause mortality among patients with stable coronary artery disease (CAD). Accordingly, the aim of this study is to explore the association between BMI and long-term all-cause mortality among patients with stable CAD.
Our study included 15,357 patients with stable CAD who were enrolled in the Bezafibrate Infarction Prevention (BIP) registry between February, 1990 and October1992, and subsequently followed-up through December 2014.
5,051 (33%) patients were classified as normal weight (BMI 18.5–24.99 kg/m²), while 7,841 (51%) patients were classified as overweight (BMI 25–29.99 kg/m²), and 2,465 (16%) as obese (BMI≥30). Kaplan-Meier survival analysis showed that at 20 years of follow-up the rate of all-cause mortality was significantly higher among obese patients (67%) compared to overweight (61%) and normal weight (61%); log rank p-value for the overall difference <0.001. Multivariable analysis showed that obese patients had an independently 12% greater mortality risk compared to normal weight patients (HR = 1.12; 95% CI 1.02–1.23; p = 0.02), whereas, overweight patients experienced a similar mortality risk as normal weight patients (HR = 0.99; 95% CI 0.92–1.06; p = 0.76). The mortality risk associated with obesity was pronounced among patients younger than 65 years (p-value for interaction<0.05).
Our findings indicate that obesity is independently associated with increased risk for long-term mortality among patients with stable coronary artery disease, whereas overweight does not appear to confer an additional risk in this population.
Overweight and Obesity
2019, Encyclopedia of Biomedical Gerontology: Volume 1-3
This article discusses the literature on overweight and obesity with a specific focus on older adults. Overweight and obesity refers to an excess of body fat relative to lean body mass. Globally data suggests that overweight and obesity are on the rise and this is likely driving the corresponding increase in metabolic syndrome. Strong evidence exists from meta-analyses that overweight and obesity is associated with increased risk of several physical and mental health conditions, but in older adults some evidence now exists that it may offer protection against some of these conditions, including mortality, particularly in clinical samples. A growing concern in older adults is that of sarcopenic obesity, highlighting a need to reduce both muscle loss and weight gain. Weight loss and conditioning advice may be best delivered to older adults by health care professionals.
Overweight and obesity
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This article discusses the literature on overweight and obesity with a specific focus on older adults. Overweight and obesity refers to an excess of body fat relative to lean body mass. Globally data suggests that overweight and obesity are on the rise and this is likely driving the corresponding increase in metabolic syndrome. Strong evidence exists from meta-analyses that overweight and obesity is associated with increased risk of several physical and mental health conditions, but in older adults some evidence now exists that it may offer protection against some of these conditions, including mortality, particularly in clinical samples. A growing concern in older adults is that of sarcopenic obesity, highlighting a need to reduce both muscle loss and weight gain. Weight loss and conditioning advice may be best delivered to older adults by health care professionals.
Impact of body mass index on long-term mortality in women and men undergoing percutaneous coronary intervention for chronic total occlusion
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The obesity paradox has been described in different patient populations. Data on the relation between obesity and outcomes in patients undergoing percutaneous coronary intervention (PCI) for chronic total occlusion (CTO) are lacking. Therefore, long-term mortality in patients undergoing CTO PCI was assessed according to different body mass index (BMI) categories.
A total of 1993 patients undergoing CTO PCI at a tertiary care center between January 2005 and December 2013 were divided into five different BMI categories: underweight, < 18.5 kg/m²; normal BMI, 18.5–24.9 kg/m²; overweight, 25.0–29.9 kg/m²; obese, 30.0–34.9 kg/m²; and very obese, ≥ 35.0 kg/m². The primary endpoint was all-cause mortality.
Median follow-up was 2.6 (interquartile range 1.1–3.1) years. Of the 1993 patients, 461 (23.1%) were of normal weight, 985 (49.4%) overweight, 396 (19.9%) obese, and 144 (7.2%) very obese. Compared with normal weight BMI patients (16.3%), overweight patients had a lower all-cause mortality (10.2%, Log Rank p = 0.001), while obese (11.1%, Log Rank p = 0.08) and severely obese (13.2%, Log Rank p = 0.39) patients had similar mortality rates. Being overweight was significantly associated with a lower all-cause mortality (HR 0.69, 95% CI 0.53–0.89, p = 0.005), and associations remained significant after multivariable adjustments for confounding factors (HR 0.73, 95% CI 0.56–0.95, p = 0.02). While being overweight was linked with a reduced all-cause mortality in men (HR 0.65, 95% CI 0.48–0.88, p = 0.005), it was not in women (HR 1.25, 95% CI 0.60–2.52, p = 0.58).
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We used the published MOOSE checklist to select the studies for this review15 (Figure 1). We identified 26 and 12 studies that reported outcomes in different BMI groups after PCI and CABG, respectively (Figure 1; Table 1).7,11-14,16-46 All studies were intermediate to low-intermediate bias risk, as assessed by using the New-Castle-Ottawa Scale (Table 2).
To investigate the relationship of body mass index (BMI) with total mortality, cardiovascular (CV) mortality, and myocardial infarction (MI) after coronary revascularization procedures (coronary artery bypass grafting [CABG] and percutaneous coronary intervention [PCI]).
Systematic search of studies was conducted using PubMed, CINAHL, Cochran CENTRAL, Scopus, and the Web of Science databases. We identified studies reporting the rate of MI, CV mortality, and total mortality among coronary artery disease patients' postcoronary revascularization procedures in various BMI categories: less than 20 (underweight), 20-24.9 (normal reference), 25-29.9 (overweight), 30-34.9 (obese), and 35 or more (severely obese). Event rates were compared using a random effects model assuming interstudy heterogeneity.
A total of 36 studies (12 CABG; 26 PCI) were selected for final analyses. The risk of total mortality (relative risk [RR], 2.59; 95% CI, 2.09-3.21), CV mortality (RR, 2.67; 95% CI, 1.63-4.39), and MI (RR, 1.79; 95% CI, 1.28-2.50) was highest among patients with low BMI at the end of a mean follow-up period of 1.7 years. The risk of CV mortality was lowest among overweight patients (RR, 0.81; 95% CI, 0.68-0.95). Increasing degree of adiposity as assessed by BMI had a neutral effect on the risk of MI for overweight (RR, 0.92; 95% CI, 0.84-1.01), obese (RR, 0.99; 95% CI, 0.85-1.15), and severely obese (RR, 0.93; 95% CI, 0.78-1.11) patients.
After coronary artery disease revascularization procedures (PCI and CABG), the risk of total mortality, CV mortality, and MI was highest among underweight patients as defined by low BMI and CV mortality was lowest among overweight patients.

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Obesity, health status, and 7-year mortality in percutaneous coronary intervention: In search of an explanation for the obesity paradox

Abstract

Background

Methods

Results

Conclusion

Introduction

Section snippets

Study population

Statistical analyses

Patient characteristics

Discussion

Limitations

Conclusion

Acknowledgments

Am J Cardiol

J Am Coll Cardiol

Ann Epidemiol

Am J Cardiol

J Am Coll Cardiol

Am J Cardiol

JACC Cardiovasc Interv

Am Heart J

Am J Clin Nutr

J Am Coll Cardiol

J Am Coll Cardiol

Am Heart J

J Clin Epidemiol

Am Heart J

Lancet

Am J Cardiol

Am J Cardiol

J Am Coll Cardiol

Chest

Med Hypotheses

Am Heart J

Am J Med

Am J Cardiol