Contribution of cardiorespiratory fitness to the obesity paradox

Complex relationship of obesity and obesity paradox in heart failure - higher risk of developing heart failure and better outcomes in established heart failure

Heart failure (HF) and obesity are major public health problems. Studies have shown that obesity may increase the risk of developing new HF but after patients have developed HF, obesity may be associated with improved outcomes. This paradoxical association of obesity with HF remains poorly understood. It is believed that the obesity paradox may in part be due to the inherent limitations of body mass index (BMI) as a measure of obesity. BMI may not appropriately measure important components of body mass like body fat, fat distribution, lean body mass, and body fluid content and may not be ideal for examining the relationship of body composition with health outcomes. Differentiating between body fat and lean body mass may explain some of the paradoxical association between higher BMI and better prognosis in patients with HF. Paradoxical outcomes in HF may also be due to phenotypes of obesity. Future studies need to develop and test metrics that may better measure body composition and may serve as a better tool for the estimation of the true association of obesity and outcomes in HF and determine whether the association may vary by obesity phenotypes. KEY MESSAGES Obesity predisposes to heart failure in all age groups. But obesity in heart failure is an area of controversy, because of obesity paradox, the apparent protective effect of overweight and mild obesity on mortality after development of heart failure. Traditional markers of obesity do not measure different components of body weight like muscle mass, fat, water, and skeletal weight. Body Mass Index in heart failure subjects does not measure accurately body fat or fluid retention. So new markers of obesity like visceral adiposity index, body composition analysis, sarcopenic status assessment may be helpful in the assessment of heart failure outcomes. Different phenotypes of obesity may be responsible for the different morbidity, mortality as well as therapeutic outcomes in heart failure.

Cardiac Effects of Obesity: PATHOPHYSIOLOGIC, CLINICAL, AND PROGNOSTIC CONSEQUENCES-A REVIEW

Obesity produces various hemodynamic alterations and changes in cardiac morphology that predispose to ventricular dysfunction and heart failure (HF). Obesity may serve as a risk factor for or the primary cause of HF. Obesity is also associated with impairment of cardiorespiratory fitness. An obesity paradox exists with respect to mortality in those with HF wherein overweight and mildly to moderately obese individuals have a better prognosis than underweight or normal weight persons. Cardiorespiratory fitness is an important determinant of the prognosis in obesity. Many of the alterations in cardiac structure and function as well as the clinical manifestations of HF are reversible with substantial weight loss in moderately to severely obese individuals.

Fitness, Fatness, and Mortality: The FIT (Henry Ford Exercise Testing) Project

BACKGROUND

The combined influence of fitness and fatness on mortality risk in diverse populations has not been adequately explored. Our aim was to assess the relative impact of exercise capacity and body mass index (BMI) on all-cause mortality.

METHODS

We included 29,257 men and women (mean age 53 years; 27% African American) from The Henry Ford Exercise Testing (FIT) Project without cardiovascular disease and diabetes mellitus at baseline. All patients completed a symptom-limited maximal treadmill stress test between 1991 and 2009. Patients were grouped for analysis by exercise capacity (≥10 metabolic equivalents of task [METs] and <10 METs) and obesity status (≥30 kg/m(2) and <30 kg/m(2)), forming 4 subgroups. Independent and joint associations of BMI and exercise capacity with all-cause mortality were assessed using Cox proportional hazard models.

RESULTS

During a mean follow-up of 10.8 years, 1898 patients (6.5%) died. We observed a strong inverse association between exercise capacity (per 1 MET unit) and all-cause mortality (hazard ratio [95% confidence interval], 0.86 [0.85-0.88]). Body mass index (per 1 BMI unit) was inversely related to mortality (hazard ratio [95% confidence interval], 0.98 [0.97-0.99]). In joint analysis, the highest mortality risk was in the <10 METs/<30 kg/m(2) subgroup.

CONCLUSIONS

Reduced exercise capacity was a strong independent risk factor for all-cause mortality in this racially diverse population. Given the comparatively limited impact of BMI, more emphasis should be placed on measuring exercise capacity and developing strategies for its improvement in cardiovascular disease prevention programs.

Comparison of the Combined Obesity Indices to Predict Cardiovascular Diseases Risk Factors and Metabolic Syndrome in Northeast China

Background: Obesity is associated with cardiovascular disease (CVD) risk factors (hypertension, dyslipidemia and diabetes) and metabolic syndrome (MetS), and it may be flawed that most studies only use one obesity index to predict these risk factors. Therefore, our study aims to compare the various combined obesity indices systematically, and to find the optimal combined obesity indices to predict CVD risk factors and MetS. Methods: A total of 16,766 participants aged 18–79 years old were recruited in Jilin Province in 2012. Receiver operating characteristic curve (ROC) curves and multiple logistic regressions were used to evaluate the predictive capacity of the combined obesity indices for CVD risk factors and MetS. Results: The adjusted area under receiver operating characteristic (AUROC) with two combined obesity indices had been improved up to 19.45%, compared with one single obesity index. In addition, body mass index (BMI) and waist circumference (WC) were the optimal combinations, where the AUROC (95% confidence interval (CI)) for hypertension, dyslipidemia, diabetes and MetS in males were 0.730 (0.718, 0.740), 0.694 (0.682, 0.706), 0.725 (0.709, 0.742) and 0.820 (0.810, 0.830), and in females were 0.790 (0.780, 0.799), 0.727 (0.717, 0.738), 0.746 (0.731, 0.761) and 0.828 (0.820, 0.837), respectively. Conclusions: The more abnormal obesity indices that one has the higher the risk for CVD risk factors and MetS, especially in males. In addition, the combined obesity indices have better predictions than one obesity index, where BMI and WC are the optimal combinations.

Associations among cardiorespiratory endurance, body mass index and blood pressure in Han Chinese children: results from the 2010 Chinese National Survey On Students' Constitution and Health

The associations among cardiorespiratory endurance (CRE), body mass index (BMI) and blood pressure (BP) in children are still unclear. This study aimed to examine the relationships among CRE, BMI and BP in Chinese children. Data were derived from the 2010 Chinese National Survey on Students' Constitution and Health. An endurance run test was used to determine CRE and children were stratified into low and high/moderate CRE groups. BMI was dichotomized into non-overweight and overweight. Among overweight children aged 7-12 years, the risk of high BP (HBP) was significantly higher in the low CRE group than in the high/moderate CRE group (in boys, odds ratio=1.13, 95% confidence interval: 1.03-1.24, P=0.010; in girls, odds ratio=1.18, 95% confidence interval: 1.04-1.33, P=0.010) after adjusting for age, BMI, socioeconomic status and area of residence. However, among all children aged 13-18 years and non-overweight children aged 7-12 years, we did not observe similar results. Higher CRE is associated with lower BP. Overweight children have a significantly higher risk of HBP and low CRE may increase the risk of HBP, independently of BMI, among 7- to 12-year-old overweight children.

Fitness but not weight status is associated with projected physical independence in older adults

Obesity and fitness have been associated with older adults' physical independence. We aimed to investigate the independent and combined associations of physical fitness and adiposity, assessed by body mass index (BMI) and waist circumference (WC) with the projected ability for physical independence. A total of 3496 non-institutionalized older adults aged 65 and older (1167 male) were included in the analysis. BMI and WC were assessed and categorized according to established criteria. Physical fitness was evaluated with the Senior Fitness Test and individual test results were expressed as Z-scores. Projected ability for physical independence was assessed with the 12-item composite physical function scale. Logistic regression was used to estimate the odds ratio (OR) for being physically dependent. A total of 30.1 % of participants were classified as at risk for losing physical independence at age 90 years. Combined fitness and fatness analysis demonstrated that unfit older adults had increased odds ratio for being physically dependent in all BMI categories (normal: OR = 9.5, 95 %CI = 6.5-13.8; overweight: OR = 6.0, 95 %CI = 4.3-8.3; obese: OR = 6.7, 95 %CI = 4.6-10.0) and all WC categories (normal: OR = 10.4, 95%CI = 6.5-16.8; middle: OR = 6.2, 95 %CI = 4.1-9.3; upper: OR = 7.0, 95 %CI = 4.8-10.0) compared to fit participants that were of normal weight and fit participants with normal WC, respectively. No increased odds ratio was observed for fit participants that had increased BMI or WC. In conclusion, projected physical independence may be enhanced by a normal weight, a normal WC, or an increased physical fitness. Adiposity measures were not associated with physical independence, whereas fitness is independently related to physical independence. Independent of their weight and WC status, unfit older adults are at increased risk for losing physical independence.

Obesity or obesities? Controversies on the association between body mass index and premature mortality

Obesity is still defined on the basis of body mass index (BMI) and BMI in itself is generally accepted as a strong predictor of overall early mortality. However, an inverse association between BMI and mortality has been reported in patients with many disease states and in several clinical settings: hemodialysis, cardiovascular diseases, hypertension, stroke, diabetes, chronic obstructive pulmonary disease, surgery, etc. This unexpected phenomenon is usually called obesity-survival paradox (OP). The contiguous concepts of metabolically healthy obesity (MHO, a phenotype having BMI ≥ 30 but not having any metabolic syndrome component and having a homeostasis model assessment of insulin resistance, HOMA, <2.5) and metabolically obese normal weight (MONW, normal-weight individuals displaying obesity-related phenotypic characteristics) have received a great deal of attention in recent years. The interactions that link MHO, MONW and OP with body composition, fat distribution, aging and cardiorespiratory fitness are other crucial areas of research. The article is an introductory narrative overview of the origin and current use of the concepts of MHO, MONW and OP. These phenomena are very controversial and appear as a consequence of the frail current diagnostic definition of obesity based only on BMI. A new commonly established characterization and classification of obesities based on a number of variables is needed urgently.

The long-term prognosis of cardiovascular disease and all-cause mortality for metabolically healthy obesity: a systematic review and meta-analysis

BACKGROUND

Metabolically healthy obese phenotype (MHO) refers to obese individuals with absence of metabolic abnormalities such as dyslipidaemia, insulin resistance and hypertension. Many studies reported the long-term prognosis of MHO on diseases and mortality with inconsistent results.

METHODS

We performed a meta-analysis to assess the risks of cardiovascular (CV) events and all-cause mortality for MHO individuals. Original prospective observational studies were searched in Medline, EMBASE, Web of Science and Cochrane library up to 30 September 2015. In this meta-analysis, the relative risk (RR) calculated on the basis of the incident number of disease events and deaths in participants and the corresponding multivariable-adjusted HR were both extracted to calculate pooled risk estimates. A random-effects model was used if there was heterogeneity among studies; otherwise, the fixed-effects model was used.

RESULTS

22 prospective studies, involving 584 799 participants, were archived in the analyses. With metabolically healthy normal weight as the reference, the MHO phenotype was associated with a higher risk of CV events (RR 1.50, 95% CI 1.27 to 1.77; HR 1.60, 95% CI 1.38 to 1.84). However, MHO individuals were not associated with increased risk of all-cause mortality (RR 1.18, 95% CI 0.83 to 1.66; HR 1.07, 95% CI 0.92 to 1.25).

CONCLUSIONS

The meta-analysis confirms a positive association between a metabolically healthy obese phenotype and the risk of CV events. However, higher risk for all-cause mortality is not evident in metabolically healthy obese individuals.

Relation of Muscle Mass and Fat Mass to Cardiovascular Disease Mortality

We evaluated the relation between components of body composition and mortality in patients with cardiovascular disease (CVD). Dual x-ray absorptiometry body composition data from the National Health and Nutrition Examination Survey 1999 to 2004 was linked to total and CVD mortality data 1999 to 2006 in 6,451 patients with CVD. Kaplan-Meier survival analysis for the end points of total and CVD mortality was plotted by quartiles of muscle mass, fat mass, and categories of body mass index (BMI). Subjects were stratified into 4 groups (low muscle/low fat mass, low muscle/high fat mass, high muscle/low fat mass, and high muscle/high fat mass). Adjusted Cox proportional hazards regression determined hazard ratios for total and CVD mortality. Rates of cardiovascular/total mortality were lower in higher quartiles of muscle mass, fat mass, and higher categories of BMI (p <0.001). The high muscle/low fat mass group had a lower risk of CVD and total mortality (risk-adjusted hazard ratios of 0.32, 95% confidence interval 0.14 to 0.73 and 0.38, 95% confidence interval 0.22 to 0.68, for CVD and total mortality, respectively). Thus, increasing fat mass, muscle mass, and BMI were all correlated with improved survival. The specific subgroup of high muscle and low fat mass had the lowest mortality risk compared with other body composition subtypes. This suggests the importance of body composition assessment in the prediction of cardiovascular and total mortality in patients with CVD.

Normal-Weight Central Obesity and Mortality Risk in Older Adults With Coronary Artery Disease

OBJECTIVE

To study the relationship between body mass index (BMI) and central obesity and mortality in elderly patients with coronary artery disease (CAD).

PATIENTS AND METHODS

We identified 7057 patients 65 years or older from 5 cohort studies assessing mortality risk using either waist circumference (WC) or waist-hip ratio (WHR) in patients with CAD from January 1, 1980, to December 31, 2008. Normal weight, overweight, and obesity were defined using standard BMI cutoffs. High WHR was defined as 0.85 or more for women and 0.90 or more for men. High WC was defined as 88 cm or more for women and 102 cm or more for men. Separate models examined WC or WHR in combination with BMI (6 categories each) as the primary predictor (referent = normal BMI and normal WC or WHR). Cox proportional hazards models investigated the relationship between these obesity categories and mortality.

RESULTS

Patients' mean age was 73.0±6.0 years (3741 [53%] women). The median censor time was 7.1 years. A normal BMI with central obesity (high WHR or high WC) demonstrated highest mortality risk (hazard ratio [HR], 1.29; 95% CI, 1.14-1.46; HR, 1.29; 95% CI, 1.12-1.50, respectively). High WHR was also predictive of mortality in the overall (HR, 2.14; 95% CI, 1.93-2.38) as well as in the sex-specific cohort. In the overall cohort, high WC was not predictive of mortality (HR, 1.04; 95% CI, 0.97-1.12); however, it predicted higher risk in men (HR, 1.12; 95% CI, 1.01-1.24).

CONCLUSION

In older adults with CAD, normal-weight central obesity defined using either WHR or WC is associated with high mortality risk, highlighting a need to combine measures in adiposity-related risk assessment.

Fitness, Body Habitus, and the Risk of Incident Type 2 Diabetes Mellitus in Korean Men

The relative contributions of cardiorespiratory fitness (CRF) and body habitus to predict incident type 2 diabetes mellitus (T2DM) remain unclear. We prospectively investigated the relation of CRF and body habitus on the risk of developing T2DM in men. Participants included 3,770 apparently healthy men who initially presented without baseline evidence of diabetes, cardiovascular disease, and hypertension. Participants were divided into 3 groups as normal weight (18.5 to 24.9 kg/m(2)), obese I (25.0 to 29.9 kg/m(2)), and obese II (≥30.0 kg/m(2)). CRF was directly measured by peak oxygen uptake (VO2peak) and categorized into unfit and fit cohorts based on the median value of age-specific VO2peak. Diabetes was defined as a glycated hemoglobin >6.5% and/or a fasting glucose >126 mg/dl at baseline and follow-up examinations. During a median follow-up of 5 years, 170 men (4.5%) developed diabetes. After adjusting for age and fasting glucose, the relative risk and 95% confidence interval (CI) for incident T2DM were 1.52 (95% CI 1.11 to 2.07) for obese I and 3.11 (95% CI 1.35 to 7.16) for obese II versus normal weight and 0.69 (95% CI 0.51 to 0.95) for fit versus unfit. However, these associations were no longer statistically significant after adjusting for potential confounders with VO2peak (1.32; 95% CI 0.96 to 1.83 for obese I and 1.61, 95% CI 0.64 to 4.06 for obese II vs normal weight) or body mass index (0.75, 95% CI 0.54 to 1.05 for fit vs unfit). In the joint analysis, obese-unfit men had 1.81 times (95% CI 1.22 to 2.69) greater risk of incident T2DM, but obese-fit men were not at increased risk of incident T2DM (0.95, 95% CI 0.57 to 1.58) compared with fit-normal weight men. In conclusion, these results suggest that both CRF and obesity predict the incidence of T2DM independent of potential confounders; however, CRF appears to attenuate the risk of developing diabetes in obese men.

Interactive Effects of Physical Fitness and Body Mass Index on the Risk of Hypertension

IMPORTANCE

High body mass index (BMI) and low physical fitness are risk factors for hypertension, but their interactive effects are unknown. Elucidation of interactions between these modifiable risk factors may help inform more effective interventions in susceptible subgroups.

OBJECTIVE

To determine the interactive effects of BMI and physical fitness on the risk of hypertension in a large national cohort.

DESIGN, SETTING, AND PARTICIPANTS

This cohort study included all 1,547,189 military conscripts in Sweden from January 1, 1969, through December 31, 1997 (97%-98% of all 18-year-old men nationwide each year), who were followed up through December 31, 2012 (maximum age, 62 years). Data analysis was conducted August 1 through August 15, 2015.

EXPOSURES

Standardized aerobic capacity, muscular strength, and BMI measurements obtained at a military conscription examination.

MAIN OUTCOMES AND MEASURES

Hypertension identified from outpatient and inpatient diagnoses.

RESULTS

A total of 93,035 men (6.0%) were diagnosed with hypertension in 39.7 million person-years of follow-up. High BMI and low aerobic capacity (but not muscular strength) were associated with increased risk of hypertension, independent of family history and socioeconomic factors (BMI, overweight or obese vs normal: incidence rate ratio, 2.51; 95% CI, 2.46-2.55; P < .001; aerobic capacity, lowest vs highest tertile: incidence rate ratio, 1.50; 95% CI, 1.47-1.54; P < .001). Aerobic capacity was inversely associated with hypertension across its full distribution (incidence rate ratio per 100 W, 0.70; 95% CI, 0.69-0.71; P < .001). A combination of high BMI (overweight or obese vs normal) and low aerobic capacity (lowest vs highest tertile) was associated with the highest risk of hypertension (incidence rate ratio, 3.53; 95% CI, 3.41-3.66; P < .001) and had a negative additive and multiplicative interaction (P < .001). Although high BMI was a significant risk factor for hypertension, low aerobic capacity also was a significant risk factor among those with normal BMI.

CONCLUSIONS AND RELEVANCE

In this large national cohort study, high BMI and low aerobic capacity in late adolescence were associated with higher risk of hypertension in adulthood. If confirmed, our findings suggest that interventions to prevent hypertension should begin early in life and include not only weight control but aerobic fitness, even among persons with normal BMI.

Smoking and reverse causation create an obesity paradox in cardiovascular disease

OBJECTIVE

Many studies find that excess weight is associated with better survival among individuals with cardiovascular disease (CVD). Investigations were carried out to see whether this "obesity paradox" can be explained by biases.

METHODS

The association between weight status and mortality in the US population ages 35 and above with CVD was investigated. Data were obtained from the National Health and Nutrition Examination Survey, 1988-2010, linked to mortality records through 2011. To minimize biases resulting from illness-induced weight loss, a reference category consisting of individuals who have always maintained normal weight was used. Age-standardized mortality rates and Cox models were estimated, comparing overweight/obesity (body mass index (BMI) ≥25.0 kg m(-2) ) to normal weight (BMI 18.5-24.9 kg m(-2) ).

RESULTS

The paradox was present among those with overweight/obesity at the time of survey (hazard ratio (HR) = 0.89; 95% confidence interval (CI) 0.78-1.01). However, when the reference category was limited to the always-normal-weight, the paradox disappeared (HR = 1.16; 95% CI 0.95-1.41). When analysis was additionally confined to never-smokers, mortality risks were significantly higher in the overweight/obesity group (HR = 1.51; 95% CI 1.07-2.15; P = 0.021).

CONCLUSIONS

The findings provide support for the hypothesis that lower mortality among individuals with CVD and overweight/obesity is a product of biases involving reverse causation and confounding by smoking.

Examining the robustness of the obesity paradox in maintenance hemodialysis patients: a marginal structural model analysis

BACKGROUND

The inverse association between body mass index (BMI) and mortality observed in patients treated with maintenance hemodialysis (MHD), also known as the obesity paradox, may be a result of residual confounding. Marginal structural model (MSM) analysis, a technique that accounts for time-varying confounders, may be more appropriate to investigate this association. We hypothesize that after applying MSM, the inverse association between BMI and mortality in MHD patients is attenuated.

METHODS

We examined the associations between BMI and all-cause mortality among 123 624 adult MHD patients treated during 2001-6. We examined baseline and time-varying BMI using Cox proportional hazards models and MSM while considering baseline and time-varying covariates, including demographics, comorbidities and markers of malnutrition and inflammation.

RESULTS

The patients included 45% women and 32% African Americans with a mean age of 61(SD 15) years. In all models, BMI showed a linear incremental inverse association with mortality. Compared with the reference (BMI 25 to <27.5 kg/m(2)), a BMI of <18 kg/m(2) was associated with a 3.2-fold higher death risk [hazard ratio (HR) 3.17 (95% CI 3.05-3.29)], and mortality risks declined with increasing BMI with the greatest survival advantage of 31% lower risk [HR 0.69 (95% CI 0.64-0.75)] observed with a BMI of 40 to <45 kg/m(2).

CONCLUSIONS

The linear inverse relationship between BMI and mortality is robust across models including MSM analyses that more completely account for time-varying confounders and biases.

Association of Body Mass Index with Clinical Outcomes in Non-Dialysis-Dependent Chronic Kidney Disease: A Systematic Review and Meta-Analysis

BACKGROUND

Previous studies have not shown a consistent link between body mass index (BMI) and outcomes such as mortality and kidney disease progression in non-dialysis-dependent chronic kidney disease (CKD) patients. Therefore, we aimed to complete a systematic review and meta-analysis study on this subject.

METHODS

We searched MEDLINE, EMBASE, Web of Science, Cumulative Index to Nursing and Allied Health Literature (CINAHL), and Cochrane Central Register of Controlled Trials (CENTRAL), and screened 7,123 retrieved studies for inclusion. Two investigators independently selected the studies using predefined criteria and assessed each study's quality using the Newcastle-Ottawa quality assessment scale. We meta-analyzed the results based on the BMI classification system by the WHO.

RESULTS

We included 10 studies (with a total sample size of 484,906) in the systematic review and 4 studies in the meta-analyses. The study results were generally heterogeneous. However, following reanalysis of the largest reported study and our meta-analyses, we observed that in stage 3-5 CKD, being underweight was associated with a higher risk of death while being overweight or obese class I was associated with a lower risk of death; however, obesity classes II and III were not associated with risk of death. In addition, reanalysis of the largest available study showed that a higher BMI was associated with an incrementally higher risk of kidney disease progression; however, this association was attenuated in our pooled results. For earlier stages of CKD, we could not complete meta-analyses as the studies were sparse and had heterogeneous BMI classifications and/or referent BMI groups.

CONCLUSION

Among the group of patients with stage 3-5 CKD, we found a differential association between obesity classes I-III and mortality compared to the general population, indicating an obesity paradox in the CKD population.

The Heart Failure Overweight/Obesity Survival Paradox: The Missing Sex Link

OBJECTIVES

This study sought to determine whether body mass index (BMI) has a differential impact on survival for females versus males with advanced systolic heart failure (HF).

BACKGROUND

Females have a survival advantage in HF, the mechanisms of which are unclear. There is also a proposed "obesity survival paradox" in which excess adiposity promotes HF survival.

METHODS

We reviewed 3,811 patients with left ventricular ejection fraction ≤40% who had undergone cardiopulmonary exercise testing between 1995 and 2011. The endpoint was all-cause mortality. Multivariable analysis was performed using a Cox proportional hazards model. Because of the nonlinearity of BMI, a restricted cubic spline was used. An interaction term was added to investigate the impact of BMI on mortality by sex.

RESULTS

The unadjusted data demonstrated an overall obesity survival paradox in HF. This survival paradox disappeared for males after adjustment for potential confounders, with overweight and obese males showing higher adjusted mortality hazard ratios compared with normal weight males. Conversely, females in the overweight BMI range (25.0 to 29.9 kg/m(2)) had the lowest adjusted mortality (hazard ratio: 0.84; 95% confidence interval: 0.77 to 0.93; p = 0.0005 compared with normal weight females) with a nadir in mortality hazard just below BMI 30 kg/m(2). The multivariable model supported a differential impact of BMI on mortality in males versus females (p for interaction <0.0001).

CONCLUSIONS

In this advanced HF cohort, an unadjusted obesity survival paradox disappeared after adjustment for confounders. Overweight and obese males had higher adjusted mortality than normal weight males, whereas a BMI in the overweight range was associated with a significant survival benefit in females.

The associations of "fatness," "fitness," and physical activity with all-cause mortality in older adults: A systematic review

OBJECTIVE

This review explored whether cardiorespiratory fitness or physical activity act as either confounders or effect modifiers of the relationship between adiposity markers and all-cause mortality in older adults.

METHODS

Systematic searches were carried out to identify observational studies that examined the association of adiposity markers (BMI, waist circumference, and waist-hip ratio) with all-cause mortality in adults aged ≥ 60 which took into account cardiorespiratory fitness or physical activity. Data from each included study was analyzed to produce a graphical representation of this relationship.

RESULTS

Fourteen of the fifteen identified studies found that increasing BMI had a non-positive association with all-cause mortality, with persistence of the obesity paradox despite adjustment for physical activity or cardiorespiratory fitness. Physical activity measurement methods were all subjective and often unvalidated. The two studies stratifying for cardiorespiratory fitness did not find that fitness had a significant impact on the relationship between excess adiposity and mortality but found that overweight and fit people had better survival than normal-weight unfit people,

CONCLUSIONS

The predominant use of poor physical activity measurement suggests that studies are currently not adequately accounting for possible physical activity confounding. More studies are needed for addressing the modification of the relationship between adiposity markers and mortality by cardiorespiratory fitness.

Metabolically Healthy Obesity and Carotid Intima-Media Thickness: Effects of Cardiorespiratory Fitness

OBJECTIVE

To test the hypothesis that cardiorespiratory fitness modifies the association between metabolically healthy obesity (MHO) phenotype and carotid intima-media thickness.

PATIENTS AND METHODS

We evaluated 3838 men (mean age, 51 ± 6 years) who participated in the general health examination program at Samsung Medical Center, Seoul, South Korea, between January 2, 2008, and December 31, 2008. Participants were divided into 4 groups on the basis of body habitus and metabolic health status using the Asia-Pacific criteria. On the basis of Asian criteria, MHO was defined as body mass index greater than or equal to 25 kg/m(2) with less than 3 metabolic abnormalities. Cardiorespiratory fitness (fitness) was directly measured by using peak oxygen uptake and divided into unfit (lower tertile of fitness) and fit (middle and upper tertiles of fitness) categories on the basis of age-specific peak oxygen uptake percentiles. The prevalence of subclinical carotid atherosclerosis was defined as a mean carotid intima-media thickness greater than the 75th percentile.

RESULTS

Compared with metabolically healthy normal weight (MHNW), MHO was associated with a higher prevalence of subclinical carotid atherosclerosis (odds ratio, 1.39; 95% CI, 1.12-1.72) after adjusting for potential confounding variables. Using multivariate logistic regression analysis, we found that the MHO unfit group had 2.00 times (95% CI, 1.48-2.73) and the metabolically unhealthy obesity unfit group had 1.84 times (95% CI, 1.26-2.67) higher risk of subclinical carotid atherosclerosis as compared with the MHNW fit group (reference group). However, MHO fit (OR, 1.25; 95% CI, 0.97-1.62) and metabolically unhealthy obesity fit (OR, 1.31; 95% CI, 0.90-1.92) groups had odds ratios for subclinical carotid atherosclerosis similar to those of the MHNW fit group.

CONCLUSION

Metabolically healthy obesity was associated with a higher prevalence of subclinical carotid atherosclerosis, but this association was attenuated by increasing levels of cardiorespiratory fitness.

Cardiorespiratory fitness attenuates risk for major adverse cardiac events in hyperlipidemic men and women independent of statin therapy: The Henry Ford ExercIse Testing Project

AIMS

We sought to evaluate the effect of cardiorespiratory fitness (CRF) in predicting mortality, myocardial infarction (MI), and revascularization in patients with hyperlipidemia after stratification by gender and statin therapy.

METHODS AND RESULTS

This retrospective cohort study included 33,204 patients with hyperlipidemia (57 ± 12 years old, 56% men, 25% black) who underwent physician-referred treadmill stress testing at the Henry Ford Health System from 1991 to 2009. Patients were stratified by gender, baseline statin therapy, and estimated metabolic equivalents from stress testing. We computed hazard ratios using Cox regression models after adjusting for demographics, cardiac risk factors, comorbidities, pertinent medications, interaction terms, and indication for stress testing.

RESULTS

There were 4,851 deaths, 1,962 MIs, and 2,686 revascularizations over a median follow-up of 10.3 years. In men and women not on statin therapy and men and women on statin therapy, each 1-metabolic equivalent increment in CRF was associated with hazard ratios of 0.86 (95% CI 0.85-0.88), 0.83 (95% CI 0.81-0.85), 0.85 (95% CI 0.83-0.87), and 0.84 (95% CI 0.81-0.87) for mortality; 0.93 (95% CI 0.90-0.96), 0.87 (95% CI 0.83-0.91), 0.89 (95% CI 0.86-0.92), and 0.90 (95% CI 0.86-0.95) for MI; and 0.91 (95% CI 0.88-0.93), 0.87 (95% CI 0.83-0.91), 0.89 (95% CI 0.87-0.92), and 0.90 (95% CI 0.86-0.94) for revascularization, respectively. No significant interactions were observed between CRF and statin therapy (P > .23).

CONCLUSION

Higher CRF attenuated risk for mortality, MI, and revascularization independent of gender and statin therapy in patients with hyperlipidemia. These results reinforce the prognostic value of CRF and support greater promotion of CRF in this patient population.

The Different Effects of BMI and WC on Organ Damage in Patients from a Cardiac Rehabilitation Program after Acute Coronary Syndrome

One of the purposes of cardiac rehabilitation (CR) after acute coronary syndrome (ACS) is to monitor and control weight of the patient. Our study is to compare the different obesity indexes, body mass index (BMI), and waist circumference (WC), through one well-designed CR program (CRP) with ACS in Guangzhou city of Guangdong Province, China, in order to identify different effects of BMI and WC on organ damage. In our work, sixty-one patients between October 2013 and January 2014 fulfilled our study. We collected the vital signs by medical records, the clinical variables of body-metabolic status by fasting blood test, and the organ damage variables by submaximal exercise treadmill test (ETT) and ultrasonic cardiogram (UCG) both on our inpatient and four-to-five weeks of outpatient part of CRP after ACS. We mainly used two-tailed Pearson's test and liner regression to evaluate the relationship of BMI/WC and organ damage. Our results confirmed that WC could be more accurate than BMI to evaluate the cardiac function through the changes of left ventricular structure on the CRP after ACS cases. It makes sense of early diagnosis, valid evaluation, and proper adjustment to ACS in CRP of the obesity individuals in the future.

Is the association of hypertension with cardiovascular events stronger among the lean and normal weight than among the overweight and obese? The multi-ethnic study of atherosclerosis

Previous studies that suggest the association of hypertension with cardiovascular disease (CVD) events is stronger in the lean/normal weight than in the obese have either included smokers, diabetics, or cancer patients, or did not account for central obesity. This study examines the interaction of adiposity with hypertension on CVD events using body mass index (BMI)-based definitions of overweight and obesity, as well as waist circumference (WC) to assess adiposity. In the Multi-Ethnic Study of Atherosclerosis, we classified 3657 nonsmoking men and women, free of baseline clinical CVD, diabetes mellitus and cancer, into 7 BMI-WC combinations defined by ethnicity-specific BMI (normal, overweight, class 1 obese, and class 2/3 obese) and ethnicity- and sex-specific WC categories (optimal or nonoptimal). Adjusted absolute event rates per 1000 person-years and relative risks (95% confidence intervals) for CVD events for hypertension (blood pressure ≥140/90 or taking medication) versus no hypertension computed within adiposity categories were 9.3 versus 1.9 and 4.96 (2.56-9.60) for normal BMI/optimal WC, 13.2 versus 4.2 and 3.13 (0.99-9.86) for normal BMI/nonoptimal WC, 9.0 versus 4.5 and 2.00 (1.19-3.36) for overweight BMI/optimal WC, 8.4 versus 5.6 and 1.50 (0.88-2.54) for overweight BMI/nonoptimal WC,14.1 versus 2.1 and 6.75 (0.69-65.57) for class 1 obese/optimal WC, 10.1 versus 3.7 and 2.69 (1.41-5.16) for class 1 obese/nonoptimal WC, and 9.9 versus 6.9 and 1.45(0.60-3.52) for class 2/3 obese/WC pooled. This study found a large relative risk of CVD events associated with hypertension for normal BMI participants and more importantly similarly high absolute risks for both normal and obese BMI with hypertension.

Obesity, metabolic syndrome and risk of atrial fibrillation: a Swedish, prospective cohort study

Aim

We aimed to investigate whether different measures of obesity could similarly predict atrial fibrillation, and whether the atrial fibrillation risk associated with obesity is dependent on presence of metabolic syndrome.

Material and Methods

We performed our study in a population-based longitudinal cardiovascular study, comprising 1 924 men and 2 097 women, aged 60 years, from Stockholm. Body mass index, waist circumference, sagittal abdominal diameter and components of metabolic syndrome (systolic- and diastolic blood pressure, fasting glucose, triglycerides, high-density lipoprotein-cholesterol) were recorded at baseline. Participants were classified by their body mass index (normal weight, overweight or obese), waist circumference (normal, semi-elevated or elevated), and according to presence of metabolic syndrome. Atrial fibrillation risk was estimated by Cox proportional hazards regression models, adjusted for common atrial fibrillation risk factors, expressed as HR and 95% CI.

Results

During a mean follow-up of 13.6 years, 285 incident atrial fibrillation cases were recorded. One standard deviation increment of each obesity measure was associated with increased atrial fibrillation risk as: body mass index 1.25 (1.12 – 1.40), waist circumference 1.35 (1.19 – 1.54) and sagittal abdominal diameter 1.28 (1.14 – 1.44). Compared to normal weight subjects without metabolic syndrome, increased atrial fibrillation risk was noted for overweight subjects with metabolic syndrome, 1.67 (1.16 – 2.41), obese subjects without metabolic syndrome, 1.75 (1.11 – 2.74) and obese subjects with metabolic syndrome, 1.92 (1.34 – 2.74). Compared to subjects with normal waist circumference without metabolic syndrome, subjects with elevated waist circumference and metabolic syndrome suffered increased atrial fibrillation risk, 2.03 (1.44 – 2.87).

Conclusions

Body mass index, waist circumference and sagittal abdominal diameter could similarly predict atrial fibrillation. Obesity was associated with an increased atrial fibrillation risk regardless of metabolic syndrome, whereas overweight and elevated waist circumference was associated with increased atrial fibrillation risk only if metabolic syndrome was present.

Sudden cardiac death and obesity

For individuals and the society as a whole, the increased risk of sudden cardiac death in obese patients is becoming a major challenge, especially since obesity prevalence has been increasing steadily around the globe. Traditional risk factors and obesity often coexist. Hypertension, diabetes, obstructive sleep apnea and metabolic syndrome are well-known risk factors for CV disease and are often present in the obese patient. Although the bulk of evidence is circumstantial, sudden cardiac death and obesity share common traditional CV risk factors. Structural, functional and metabolic factors modulate and influence the risk of sudden cardiac death in the obese population. Other risk factors such as left ventricular hypertrophy, increased number of premature ventricular complexes, altered QT interval and reduced heart rate variability are all documented in both obese and sudden cardiac death populations. The present review focuses on out-of-hospital sudden cardiac death and potential mechanisms leading to sudden cardiac death in this population.

Reverse epidemiology in different stages of heart failure

BACKGROUND

In heart failure (HF), traditional cardiovascular risk factors (RF) as body mass index (BMI), total cholesterol (TC) and systolic blood pressure (SBP) are associated with better survival. It is unknown at which time point along the disease continuum the adverse impact of these RF ceases and may 'start to reverse'. We analyzed the distribution of RF and their association with survival across HF stages.

METHODS

We pooled data from four cohort studies from the German Competence Network HF. Employing ACC/AHA-criteria, patients were allocated to stage A (n=218), B (n=1324), C1 (i.e., New York Heart Association [NYHA] classes I & II; n=1134), and C2+D (NYHA III & IV; n=639).

RESULTS

With increasing HF severity median age increased (63/67/67/70 years), whereas the proportion of females (56/52/37/35%), median BMI (26.1/28.8/27.7/26.6 kg/m(2)), TC (212/204/191/172 mg/dl), and SBP (140/148/130/120 mmHg) decreased (P<0.001 for trend for all). In the total cohort, higher levels of all RF were associated with better survival, even after extensive adjustment for multiple confounders. If analyses were stratified, however, a higher RF burden predicted better survival only in clinically symptomatic patients: hazard ratio (HR) per +2 kg/m(2) BMI 0.91 (95% confidence interval 0.88; 0.95); per +10 mg/dl TC 0.93 (0.92; 0.95); per +5 mmHg SBP 0.94 (0.92; 0.95).

CONCLUSION

In this well-characterized sample of patients representing the entire HF continuum, reverse associations were only consistently observed in symptomatic HF stages. Our data indicate that the phenomenon of a "reverse epidemiology" in HF is subject to significant selection bias in less advanced disease.

Changes in mid-life fitness predicts heart failure risk at a later age independent of interval development of cardiac and noncardiac risk factors: the Cooper Center Longitudinal Study

AIMS

Low mid-life fitness is associated with higher risk for heart failure (HF). However, it is unclear to what extent this HF risk is modifiable and mediated by the burden of cardiac and noncardiac comorbidities. We studied the effect of cardiac and noncardiac comorbidities on the association of mid-life fitness and fitness change with HF risk.

METHODS

Linking individual subject data from the Cooper Center Longitudinal Study (CCLS) with Medicare claims files, we studied 19,485 subjects (21.2% women) who survived to receive Medicare coverage from 1999 to 2009. Fitness estimated by Balke treadmill time at mean age of 49 years was analyzed as a continuous variable (in metabolic equivalents [METs]) and according to age- and sex-specific quintiles. Associations of mid-life fitness and fitness change with HF hospitalization after age of 65 years were assessed by applying a proportional hazards recurrent events model to the failure time data with each comorbidity entered as time-dependent covariates.

RESULTS

After 127,110 person years of Medicare follow-up, we observed 1,038 HF hospitalizations. Higher mid-life fitness was associated with a lower risk for HF hospitalization (hazard ratio [HR] 0.82 [0.76-0.87] per MET) after adjustment for traditional risk factors. This remained unchanged after further adjustment for the burden of Medicare-identified cardiac and noncardiac comorbidities (HR 0.83 [0.78-0.89]). Each 1 MET improvement in mid-life fitness was associated with a 17% lower risk for HF hospitalization in later life (HR 0.83 [0.74-0.93] per MET).

CONCLUSIONS

Mid-life fitness is an independent and modifiable risk factor for HF hospitalization at a later age.

Body fat percentage, body mass index and waist-to-hip ratio as predictors of mortality and cardiovascular disease

OBJECTIVE

To study the utility of body fat percentage in predicting health outcomes when other obesity indices are considered.

METHODS

We conducted a prospective cohort study to evaluate the independent utility of body fat percentage and other obesity indices in predicting mortality and cardiovascular disease (CVD).

RESULTS

We prospectively followed 15 062 European Prospective Investigation into Cancer (EPIC)-Norfolk participants who attended a health examination during 1997–2000 for all-cause mortality and incidence of CVD up to end of December 2011 and end of March 2009, respectively. During the follow-up, 2420 died and 4665 had incident CVD. After exclusion of prior stroke, myocardial infarction and cancer and adjusting for potential confounders, body mass index (BMI) and waist-to- hip ratio (WHR), the HR of mortality for men were 0.86 (0.68 to 1.09), 0.81 (0.61 to 1.07) and 0.76 (0.55 to 1.05) and for women were 0.91 (0.70 to 1.17), 0.75 (0.55 to 1.02) and 0.87 (0.61 to 1.23) for second, third and fourth quartile compared with the first (bottom) quartile of body fat percentage. The respective HRs for incident CVD were 0.99 (0.83 to 1.19), 0.85 (0.69 to 1.04) and 0.81 (0.64 to 1.03) for men and 0.98 (0.82 to 1.17), 0.89 (0.73 to 1.10) and 1.02 (0.81 to 1.29) for women. In contrast, higher BMI and WHR were associated with an increased risk of both outcomes and WHR appeared to have the best predictive value among three indices.

CONCLUSIONS

Once BMI and WHR are taken into account, fat percentage does not add to prediction of mortality or CVD in middle-aged and older-aged adults.

Counterintuitive relationship between visceral fat and all-cause mortality in an elderly Asian population

OBJECTIVE

Abdominal obesity is considered to be a risk factor for mortality. However, recent studies indicate that overweight may be negatively associated with mortality ("obesity paradox"). The relationships between mortality and various obesity markers in an elderly Asian cohort were evaluated.

METHODS

Subjects of the Korean Longitudinal Study on Health and Aging (KLoSHA) (n = 1000, age ≥65 years) were included. The visceral fat area (VFA) and subcutaneous fat area (SFA) were measured using computed tomography.

RESULTS

A total of 222 deaths occurred during the 6-year follow-up (median = 5.2 [range 0.1-6.3] years). Body mass index (BMI), VFA, SFA, and total fat mass were negatively associated with all-cause mortality in the univariable analyses (hazard ratio [HR] 0.67 per 1 SD [95% CI 0.57-0.77], 0.66 [0.55-0.79], 0.73 [0.61-0.86], and 0.74 [0.63-0.87], respectively). BMI and VFA were significantly associated with all-cause mortality in the multivariable analyses (HR 0.85 per 1 SD [95% CI 0.73-0.99] and 0.64 [0.47-0.87], respectively). When stratified by quartiles, the HR associated with VFA was the lowest in the third quartile.

CONCLUSIONS

In this observational study with a short follow-up of elderly Asian people, higher amounts of visceral fat, a marker for central obesity, were associated with decreased all-cause mortality.

Healthy obese versus unhealthy lean: the obesity paradox

Overweight and obesity have reached epidemic proportions in the USA and most of the rest of the world. Particularly concerning is the very high prevalence of class III obesity (BMI ≥40 kg/m(2)), which has reached ∼3% in the USA. In the past few years, controversy has surrounded the idea that some individuals with obesity can be considered healthy with regards to their metabolic and cardiorespiratory fitness, which has been termed the 'obesity paradox'. These controversies are reviewed in detail here, including discussion of the very favourable prognosis in patients with obesity who have no notable metabolic abnormalities and who have preserved fitness. The article also discusses the suggestion that greater emphasis should be placed on improving fitness rather than weight loss per se in the primary and secondary prevention of cardiovascular diseases, at least in patients with overweight and class I obesity (BMI 30-35 kg/m(2)).

Weight loss and physical activity for disease prevention in obese older adults: an important role for lifestyle management

Weight loss in older adults has been a controversial topic for more than a decade. An obesity paradox has been previously described and the issue of weight status on health outcomes remains a highly debated topic. However, there is little doubt that physical activity (PA) has a myriad of benefits in older adults, especially in obese individuals who are inactive and have a poor cardiometabolic profile. In this review, we offer a critical view to clarify misunderstandings regarding the obesity paradox, particularly as it relates to obese older adults. We also review the evidence on PA and lifestyle interventions for the improvement of cardiorespiratory fitness, which can prevent disease and provide benefits to obese older adults, independent of weight changes.

Obesity and cardiovascular diseases: implications regarding fitness, fatness, and severity in the obesity paradox

Obesity has been increasing in epidemic proportions, with a disproportionately higher increase in morbid or class III obesity, and obesity adversely affects cardiovascular (CV) hemodynamics, structure, and function, as well as increases the prevalence of most CV diseases. Progressive declines in physical activity over 5 decades have occurred and have primarily caused the obesity epidemic. Despite the potential adverse impact of overweight and obesity, recent epidemiological data have demonstrated an association of mild obesity and, particularly, overweight on improved survival. We review in detail the obesity paradox in CV diseases where overweight and at least mildly obese patients with most CV diseases seem to have a better prognosis than do their leaner counterparts. The implications of cardiorespiratory fitness with prognosis are discussed, along with the joint impact of fitness and adiposity on the obesity paradox. Finally, in light of the obesity paradox, the potential value of purposeful weight loss and increased physical activity to affect levels of fitness is reviewed.