Obesity paradox or inappropriate study designs? Time for life-course epidemiology

Lifetime Body Mass Index Trajectories and Contrasting Lung Function Abnormalities in Mid-Adulthood: Data From the Tasmanian Longitudinal Health Study

BACKGROUND AND OBJECTIVE

The impact of lifetime body mass index (BMI) trajectories on adult lung function abnormalities has not been investigated previously. We investigated associations of BMI trajectories from childhood to mid-adulthood with lung function deficits and COPD in mid-adulthood.

METHODS

Five BMI trajectories (n = 4194) from age 5 to 43 were identified in the Tasmanian Longitudinal Health Study. Lung function outcomes were defined using spirometry at 45 and 53 years. Associations between these BMI trajectories and lung function outcomes were investigated using multivariable regression.

RESULTS

Compared to the average BMI trajectory, the child's average-increasing BMI trajectory was associated with greater FVC decline from 45 to 53 years (β = -178 mL; 95% CI -300.6, -55.4), lower FRC, ERV and higher TLco at 45 years, lower FVC (-227 mL; -345.3, -109.1) and higher TLco at 53 years. The High BMI trajectory was also associated with lower FRC, ERV and higher TLco at 45 years, while spirometric restriction (OR = 6.9; 2.3, 21.1) and higher TLco at 53 years. The low BMI trajectory was associated with an obstructive picture: lower FEV1 (-124 mL; -196.4, -51.4) and FVC (-91 mL; -173.4, -7.7), and FEV1/FVC (-1.2%; -2.2, -0.1) and higher ERV and lower TLco at 45 and 53 years. A similar pattern was found at 53 years. No associations were observed with spirometrically defined COPD.

CONCLUSION

Our findings revealed contrasting lung function abnormalities were associated with high, subsequently increasing, and low BMI trajectories. These results emphasise the importance of tracking changes in BMI over time and the need to maintain an average BMI trajectory (BMI-Z-score 0 at each time point) throughout life.

Obesity in Relation to Renal Cell Carcinoma Incidence and Survival in Three Prospective Studies

To disentangle the "obesity paradox" in renal cell carcinoma (RCC), we examined associations of body mass index (BMI) and weight change with RCC risk and survival in the Health Professionals Follow-up Study (HPFS) and Nurses' Health Study (NHS) 1 and 2. We estimated cohort-specific and summary covariable-adjusted hazard ratios (HRs) and 95% confidence intervals (CIs) for RCC incidence, as well as RCC-specific survival among cases in the pooled HPFS and NHS data. Cumulative average BMI was associated with a higher risk of total RCC (summary HR 2.16, 95% CI 1.77-2.63 for BMI ≥30 vs 18-<25 kg/m²; p trend <0.001) and fatal RCC (HR 2.03, 95% CI 1.37-3.01; p trend <0.001). Prediagnosis BMI was not associated with RCC death. However, first postdiagnosis BMI (HR 0.51, 95% CI 0.29-0.89; p trend 0.006) and prediagnosis to postdiagnosis weight change (HR 0.52, 95% CI 0.29-0.91; p trend 0.001) were significantly inversely associated with RCC death. These results support obesity as a risk factor for total and fatal RCC. They undermine the obesity paradox by suggesting that weight loss around diagnosis, and not low BMI itself, is associated with worse prognosis. PATIENT SUMMARY: We studied obesity in kidney cancer and found that obesity is associated with getting and dying from the disease. Body mass index at diagnosis is not an ideal factor for predicting prognosis, as patients who have lost weight are likely to have more aggressive cancer.

Impact of lifetime body mass index trajectories on the incidence and persistence of adult asthma

BACKGROUND

High body mass index trajectories from childhood to adulthood are associated with development of some chronic diseases, but whether such trajectories influence adult asthma has not been investigated to date. Therefore, we investigated associations between body mass index trajectories from childhood to middle age (5-43 years) and incidence, persistence, and relapse of asthma from ages 43 to 53 years.

METHODS

In the Tasmanian Longitudinal Health Study (n= 4194), weight and height were recorded at 8-time points between 5 and 43 years. body mass index trajectories were developed using group-based trajectory modelling. Associations between body mass index trajectories and asthma incidence, persistence, and relapse from 43 to 53 years; bronchial hyper-responsiveness at 50 years; and bronchodilator responsiveness at 53 years were modelled using multiple logistic and linear regression.

RESULTS

Five distinct body mass index trajectories were identified: average, low, high, child high-decreasing, and child average-increasing. Compared to the average trajectory, child average-increasing and high trajectories were associated with increased risk of incident asthma (OR=2.6; 95%CI 1.1, 6.6 and OR=4.4; 1.7, 11.4, respectively) and bronchial hyper-responsiveness in middle age (OR= 2.9; 1.1, 7.5 and OR= 3.5;1.1, 11.4, respectively). No associations were observed for asthma persistence or relapse.

CONCLUSION

Participants with child average-increasing and high body mass index trajectories from childhood to middle age were at higher risk of incident adult asthma. Thus, encouraging individuals to maintain normal body mass index over the life course may help reduce the burden of adult asthma.

The ambiguous role of obesity in oncology by promoting cancer but boosting antitumor immunotherapy

Obesity is nowadays considered a pandemic which prevalence's has been steadily increasingly in western countries. It is a dynamic, complex, and multifactorial disease which propitiates the development of several metabolic and cardiovascular diseases, as well as cancer. Excessive adipose tissue has been causally related to cancer progression and is a preventable risk factor for overall and cancer-specific survival, associated with poor prognosis in cancer patients. The onset of obesity features a state of chronic low-grade inflammation and secretion of a diversity of adipocyte-derived molecules (adipokines, cytokines, hormones), responsible for altering the metabolic, inflammatory, and immune landscape. The crosstalk between adipocytes and tumor cells fuels the tumor microenvironment with pro-inflammatory factors, promoting tissue injury, mutagenesis, invasion, and metastasis. Although classically established as a risk factor for cancer and treatment toxicity, recent evidence suggests mild obesity is related to better outcomes, with obese cancer patients showing better responses to treatment when compared to lean cancer patients. This phenomenon is termed obesity paradox and has been reported in different types and stages of cancer. The mechanisms underlying this paradoxical relationship between obesity and cancer are still not fully described but point to systemic alterations in metabolic fitness and modulation of the tumor microenvironment by obesity-associated molecules. Obesity impacts the response to cancer treatments, such as chemotherapy and immunotherapy, and has been reported as having a positive association with immune checkpoint therapy. In this review, we discuss obesity's association to inflammation and cancer, also highlighting potential physiological and biological mechanisms underlying this association, hoping to clarify the existence and impact of obesity paradox in cancer development and treatment.

Moderate physical activity may not decrease the risk of cardiovascular disease in persistently overweight and obesity adults

Background

Body mass index (BMI) and physical activity (PA) has been documented to be associated with cardiovascular disease (CVD). However, the evidences regarding joint phenotypes of BMI and PA trajectories with risk for CVD and all-cause mortality are still limited.

Methods

Participants from the Kailuan Study, followed up during 2006–2019 were included, with primary outcomes of CVDs (myocardial infarction or stroke) and all-cause mortality. BMI and PA were repeatedly measured at least three times, and thus joint phenotypes trajectory groups were identified by group-based trajectory modeling. Cox proportional hazards models were used to examine the associations between trajectory groups and CVDs and all-cause mortality.

Results

Totally 88,141 (6 trajectories) and 89,736 participants (5 trajectories) were included in the final analyses relating trajectories to CVDs and all-cause mortality, respectively. Compared with persistent normal-weight with moderate PA group, participants were associated with increased risk of CVD in persistent overweight with moderate PA trajectory group (adjusted hazard ratio [aHR]: 1.31, 95% confidence interval [CI]: 1.22–1.41) and persistent obesity with moderate PA trajectory group (aHR: 1.55, 95% CI: 1.41–1.69). While the rising to overweight with moderate PA in normal-weight status with active PA (aHR: 0.72, 95% CI: 0.65–0.79), persistent overweight with moderate PA (aHR: 0.92, 95% CI: 0.87–0.97) and decline to normal-weight in overweight status with moderate PA (aHR: 0.73, 95% CI: 0.67–0.80) trajectories group were significantly associated with decreased all-cause mortality risk. The associations remained robust among stratifying by age and sex individuals and sensitive analysis.

Conclusions

The long-term trajectories analysis showed that moderate PA may not decrease the risk of CVD in persistently overweight and obesity adults.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12967-021-03212-7.

Obesity, Body Composition, and Sex Hormones: Implications for Cardiovascular Risk

Cardiovascular disease (CVD) continues to be the leading cause of death in adults, highlighting the need to develop novel strategies to mitigate cardiovascular risk. The advancing obesity epidemic is now threatening the gains in CVD risk reduction brought about by contemporary pharmaceutical and surgical interventions. There are sex differences in the development and outcomes of CVD; premenopausal women have significantly lower CVD risk than men of the same age, but women lose this advantage as they transition to menopause, an observation suggesting potential role of sex hormones in determining CVD risk. Clear differences in obesity and regional fat distribution among men and women also exist. While men have relatively high fat in the abdominal area, women tend to distribute a larger proportion of their fat in the lower body. Considering that regional body fat distribution is an important CVD risk factor, differences in how men and women store their body fat may partly contribute to sex-based alterations in CVD risk as well. This article presents findings related to the role of obesity and sex hormones in determining CVD risk. Evidence for the role of sex hormones in determining body composition in men and women is also presented. Lastly, the clinical potential for using sex hormones to alter body composition and reduce CVD risk is outlined. © 2022 American Physiological Society. Compr Physiol 12:1-45, 2022.

BMI and risk of all-cause mortality in normotensive and hypertensive adults: the rural Chinese cohort study

OBJECTIVE

The impact of baseline hypertension status on the BMI-mortality association is still unclear. We aimed to examine the moderation effect of hypertension on the BMI-mortality association using a rural Chinese cohort.

DESIGN

In this cohort study, we investigated the incident of mortality according to different BMI categories by hypertension status.

SETTING

Longitudinal population-based cohort.

PARTICIPANTS

17 262 adults ≥18 years were recruited from July to August of 2013 and July to August of 2014 from a rural area in China.

RESULTS

During a median 6-year follow-up, we recorded 1109 deaths (610 with and 499 without hypertension). In adjusted models, as compared with BMI 22-24 kg/m2, with BMI ≤ 18, 18-20, 20-22, 24-26, 26-28, 28-30 and >30 kg/m2, the hazard ratios for mortality in normotensive participants were 1·92 (95% CI 1·23, 3·00), 1·44 (95% CI 1·01, 2·05), 1·14 (95% CI 0·82, 1·58), 0·96 (95% CI 0·70, 1·31), 0·96 (95% CI 0·65, 1·43), 1·32 (95% CI 0·81, 2·14) and 1·32 (95% CI 0·74, 2·35), respectively, and in hypertensive participants were 1·85 (95% CI 1·08, 3·17), 1·67 (95% CI 1·17, 2·39), 1·29 (95% CI 0·95, 1·75), 1·20 (95% CI 0·91, 1·58), 1·10 (95% CI 0·83, 1·46), 1·10 (95% CI 0·80, 1·52) and 0·61 (95% CI 0·40, 0·94), respectively. The risk of mortality was lower in individuals with hypertension with overweight or obesity v. normal weight, especially in older hypertensives (≥60 years old). Sensitivity analyses gave consistent results for both normotensive and hypertensive participants.

CONCLUSIONS

Low BMI was significantly associated with increased risk of all-cause mortality regardless of hypertension status in rural Chinese adults, but high BMI decreased the mortality risk among individuals with hypertension, especially in older hypertensives.

Does Body Mass Index Impact the Outcome of Stroke Patients Who Received Intravenous Thrombolysis?

BACKGROUND

We sought to investigate the effect of obesity and BMI on functional outcome and rate of symptomatic intracranial hemorrhage (sICH) in a large sample of patients with acute ischemic stroke (AIS) treated with intravenous thrombolysis (IVT).

METHODS

In a single-center retrospective, but prospectively collected data, study of patients with AIS treated with IVT in a 10-year period, patients were placed into groups based on their BMI defined as underweight (<18.5 kg/m2), normal weight (18.5-24.9 kg/m2), overweight (25-29.9 kg/m2), or obese (<30 kg/m2). The rate of sICH and discharge modified Rankin Scale (mRS) were compared between the groups using logistic regression analysis.

RESULTS

In a total of 834 patients who received IVT for AIS during a 10-year period, 224 (27.0%) were obese. Obese patients did not have a higher rate of sICH after IVT for AIS on the unadjusted or adjusted analysis (adjusted OR 0.95, 95% CI 0.48-1.88). We did not find an association between obesity and poor functional outcome at discharge (adjusted OR 0.76, 95% CI 0.53-1.09).

CONCLUSIONS

After adjusting for confounding factors such as age, baseline National Institute of Health Stroke Scale (NIHSS), and comorbidities, obesity was not associated with an unfavorable functional outcome at discharge nor with a higher risk of sICH in patients with AIS treated with IVT.

Latent Class Trajectory Modeling of Adult Body Mass Index and Risk of Obesity-Related Cancer: Findings from the Melbourne Collaborative Cohort Study

BACKGROUND

Obesity increases the risk of 13 cancer types. Given the long process of carcinogenesis, it is important to determine the impact of patterns of body mass over time.

METHODS

Using data from 30,377 participants in the Melbourne Collaborative Cohort Study, we identified body mass index (BMI) trajectories across adulthood and examined their association with the risk of obesity-related cancer. Participants completed interviews and questionnaires at baseline (1990-1994, age 40-69 years), follow-up 1 (1995-1998), and follow-up 2 (2003-2005). Body mass was recalled for age 18 to 21 years, measured at baseline, self-reported at follow-up 1, and measured at follow-up 2. Height was measured at baseline. Cancer diagnoses were ascertained from the Victorian Cancer Registry and the Australian Cancer Database. A latent class trajectory model was used to identify BMI trajectories that were not defined a priori. Cox regression was used to estimate HRs and 95% confidence intervals (CI) of obesity-related cancer risks by BMI trajectory.

RESULTS

Six distinct BMI trajectories were identified. Compared with people who maintained lower normal BMI, higher risks of developing obesity-related cancer were observed for participants who transitioned from normal to overweight (HR, 1.29; 95% CI, 1.13-1.47), normal to class I obesity (HR, 1.50; 95% CI, 1.28-1.75), or from overweight to class II obesity (HR, 1.66; 95% CI, 1.32-2.08).

CONCLUSIONS

Our findings suggest that maintaining a healthy BMI across the adult lifespan is important for cancer prevention.

IMPACT

Categorization of BMI by trajectory allowed us to identify specific risk groups to target with public health interventions.

[The «obesity paradox» and its degree of proof]

The article gives a critical assessment of the so-called obesity paradox. Methodological errors that occur in the organization of studies that studied the obesity paradox and the formation of comparison groups are highlighted. There are also examples of the disappearance of the obesity paradox when taking into account additional risk factors. The organization of prospective studies or more careful consideration of all currently known risk factors for cardiovascular diseases (CVD) will significantly improve the results of the study of the effect of overweight and obesity on mortality in patients with CVD. Thus, despite the biological possibility of the existence of a positive effect of adipose tissue in CVD, the presence of a large number of errors identified in the analysis of the work of researchers obesity paradox require to reconsider the existence of this phenomenon, it should be taken into account the possibility that the obesity paradox may be a consequence of improper design studies to investigate this phenomenon.

Obesity paradox in subarachnoid hemorrhage: a systematic review

As the number of obese people is globally increasing, reports about the putative protective effect of obesity in life-threatening diseases, such as subarachnoid hemorrhage (SAH), are gaining more interest. This theory-the obesity paradox-is challenging to study, and the impact of obesity has remained unclear in survival of several critical illnesses, including SAH. Thus, we performed a systematic review to clarify the relation of obesity and SAH mortality. Our study protocol included systematic literature search in PubMed, Scopus, and Cochrane library databases, whereas risk-of-bias estimation and quality of each selected study were evaluated by the Critical Appraisal Skills Program and Cochrane Collaboration guidelines. A directional power analysis was performed to estimate sufficient sample size for significant results. From 176 reviewed studies, six fulfilled our eligibility criteria for qualitative analysis. One study found paradoxical effect (odds ratio, OR = 0.83 (0.74-0.92)) between morbid obesity (body mass index (BMI) > 40) and in-hospital SAH mortality, and another study found the effect between continuously increasing BMI and both short-term (OR = 0.90 (0.82-0.99)) and long-term SAH mortalities (OR = 0.92 (0.85-0.98)). However, according to our quality assessment, methodological shortcomings expose all reviewed studies to a high-risk-of-bias. Even though two studies suggest that obesity may protect SAH patients from death in the acute phase, all reviewed studies suffered from methodological shortcomings that have been typical in the research field of obesity paradox. Therefore, no definite conclusions could be drawn.

Body mass index and clinical outcomes in patients after ischaemic stroke in South Korea: a retrospective cohort study

OBJECTIVES

Although obesity is a risk factor for stroke, its impact on mortality in patients with stroke remains unclear. In this study, we aimed to evaluate the relationship between body mass index (BMI) and mortality due to ischaemic stroke among adults aged 20 years and above in Korea.

DESIGN

Retrospective cohort study.

SETTING

A tertiary-hospital-based stroke registry linked to the death records.

PARTICIPANTS

3599 patients admitted for ischaemic stroke from January 2007 to June 2013.

OUTCOME MEASURES

The HRs for all-cause and stroke-related mortality were calculated using Cox proportional hazards models. Progression from stroke-related mortality was assessed using the Fine-Grey competing risk model, treating other-cause mortality as a competing risk. Adjustments were made for age, gender, smoking status, Charlson comorbidity index, cardiovascular or non-cardiovascular comorbidities, stroke severity, severity related to other medical conditions, complications and enrolment year. We repeated the analysis with stratification based on age groups (less than 65 vs 65 years and above).

RESULTS

For stroke-related mortality, there was no significant difference among the four BMI groups. The risk of all-cause mortality was 36% higher in the underweight group than in the normal weight group (long-term HR=1.36, 95% CI: 1.04 to 1.79), whereas the mortality risk of the obese group was significantly lower (HR=0.66, 95% CI: 0.54 to 0.81). Although this relationship was not estimated in the younger group, it was found that obesity had a protective effect on the all-cause mortality in the elderly (long-term HR=0.66, 95% CI: 0.52 to 0.83).

CONCLUSIONS

Obesity is more likely to reduce mortality risk than normal weight, especially in elderly patients.

Trajectories of body mass index in adulthood and all-cause and cause-specific mortality in the Melbourne Collaborative Cohort Study

OBJECTIVE

Limited research has assessed the association between patterns of body mass index (BMI) change across adulthood and mortality. We aimed to identify groups of individuals who followed specific group-based BMI trajectories across adulthood, using weight collected on three occasions and recalled data from early adulthood, and to examine associations with all-cause and cause-specific mortality.

DESIGN

Prospective cohort study.

SETTING

Melbourne, Australia.

PARTICIPANTS

Adults (n=29 881) enrolled in the Melbourne Collaborative Cohort Study, who were aged from 40 to 70 years between 1990 and 1994, and had BMI data for at least three time points.

OUTCOME

Deaths from any cause before 31 March 2017 and deaths from obesity-related cancers, cardiovascular diseases (CVDs) and other causes before 31 December 2013.

RESULTS

We identified six group-based BMI trajectories: lower-normal stable (TR1), higher-normal stable (TR2), normal to overweight (TR3), chronic borderline obesity (TR4), normal to class I obesity (TR5) and overweight to class II obesity (TR6). Generally, compared with maintaining lower-normal BMI throughout adulthood, the lowest mortality was experienced by participants who maintained higher-normal BMI (HR 0.90; 95% CI 0.84 to 0.97); obesity during midlife was associated with higher all-cause mortality even when BMI was normal in early adulthood (HR 1.09; 95% CI 0.98 to 1.21) and prolonged borderline obesity from early adulthood was also associated with elevated mortality (HR 1.16; 95% CI 1.01 to 1.33). These associations were stronger for never-smokers and for death due to obesity-related cancers. Being overweight in early adulthood and becoming class II obese was associated with higher CVD mortality relative to maintaining lower-normal BMI (HR 2.27; 95% CI 1.34 to 3.87).

CONCLUSION

Our findings highlight the importance of weight management throughout adulthood to reduce mortality.

The Plausibility of Obesity Paradox in Cancer-Point

In contrast to the convincing evidence that obesity (measured by body mass index, BMI) increases the risk of many different types of cancer, there is an ambiguity in the role of obesity in survival among cancer patients. Some studies suggested that higher BMI decreased mortality risk in cancer patients, a phenomenon called the obesity paradox. The spurious positive association between BMI and cancer survival is likely to be explained by several methodologic limitations including confounding, reverse causation, and collider stratification bias. Also, the inadequacy of BMI as a measure of body fatness in cancer patients commonly experiencing changes in body weight and body composition may have resulted in the paradox. Other factors contributing to the divergent results in literature are significant heterogeneity in study design and method (e.g., study population, follow-up length); time of BMI assessment (pre-, peri-, or post-diagnosis); and lack of consideration for variability in the strength and directions of associations by age, sex, race/ethnicity, and cancer subtype. Robust but practical methods to accurately assess body fatness and body compositions and weight trajectories in cancer survivors are needed to advance this emerging field and to develop weight guidelines to improve both the length and the quality of cancer survival. Cancer Res; 78(8); 1898-903. ©2018 AACR.

Obesity-Stroke Paradox Exists in Insulin-Resistant Patients But Not Insulin Sensitive Patients

Background and Purpose- The underlying mechanisms of stroke-obesity paradox are still not fully understood. This study aims to investigate the contribution of insulin resistance to the association between body mass index and stroke outcomes. Methods- Patients with ischemic stroke without history of diabetes mellitus in the Abnormal Glucose Regulation in Patients With Acute Stroke Across-China registry were included. Overweight or obese was defined as body mass index ≥23, and the median of homeostasis model assessment-insulin resistance index was chosen as cutoff to define insulin resistance. Cox or logistic regression model was used to assess the interaction between body mass index and homeostasis model assessment-insulin resistance on 1-year prognosis (all-cause mortality and poor functional outcome defined as modified Rankin Scale score 3-6). Results- Of 1227 study participants, the median homeostasis model assessment-insulin resistance was 1.9 (interquartile range, 1.1-3.1) and 863 (70.3%) patients were classified as overweight or obese. Among insulin-resistant patients, overweight/obese patients experienced one-half of the risk of death after stroke than their low/normal weight counterparts (9.42% versus 17.69%, unadjusted hazard ratio, 0.50; 95% CI, 0.31-0.82), while among insulin-sensitive ones, no significant difference of mortality risk was found (7.58% versus 6.91%, 1.07; 0.57-1.99). Similar trends were observed for poor functional outcome. Results were similar after adjustments for confounders. There were significant interactions between body mass index and homeostasis model assessment-insulin resistance on the risks of mortality (P=0.045) and poor functional outcome (P=0.049). Conclusions- We observed the obesity paradox for mortality and functional outcome in insulin-resistant patients but did not find the obesity paradox in insulin-sensitive patients. Insulin resistance may be one of the mechanisms underlying the obesity paradox of the outcome in patients with ischemic stroke.

Body Mass Index and Clinical Outcomes in Large Vessel Occlusion Acute Ischemic Stroke after Endovascular Therapy

Background and Purpose

Several reports have described lower mortality rates in overweight or obese patients as compared to normal weight ones. In the past decade, several studies have investigated the phenomenon, commonly known as the obesity paradox, with mixed results thus far. We sought to determine whether outcomes differ between patients with large vessel occlusion strokes (LVOS) after endovascular therapy (ET) according to their body mass index (BMI).

Methods

We reviewed our prospectively collected endovascular database at a tertiary care academic institution. All patients that underwent ET for acute LVOS were categorized according to their BMI into 4 groups: (1) underweight (BMI < 18.5), (2) normal weight (BMI = 18.5-25), (3) overweight (BMI = 25-30), and (4) obese (BMI > 30). Baseline characteristics, procedural radiological as well as outcome parameters where compared.

Results

A total of 926 patients qualified for the study, of which 20 (2.2%) were underweight, 253 (27.3%) had a normal weight, 315 (34%) were overweight, and 338 (36.5%) were obese. When compared with normal weight (reference), overweight patients were younger, had higher rates of dyslipidemia and diabetes and higher glucose levels, while obese patients were younger, less often smokers, and had higher rates of hypertension and diabetes and higher glucose levels. Other baseline and procedural characteristics were comparable. The rates of successful reperfusion (modified treatment in cerebral ischemia, 2b-3), parenchymal hematomas, 90-day good clinical outcomes (modified Rankin scale, 0-2), and 90-day mortality were comparable between groups. On multivariate analysis, BMI was not associated with good outcomes nor mortality.

Conclusion

In patients treated with mechanical thrombectomy, BMI is not associated with outcomes. However, patients who are overweight or obese have more comorbidities and a higher stroke risk and, thus, should strive for a normal weight.

Impact of Normal Weight Central Obesity on Clinical Outcomes in Male Patients With Premature Acute Coronary Syndrome

There is a lack of studies that evaluate the association between normal weight central obesity and subsequent outcomes in patients with premature acute coronary syndrome (ACS). We evaluated 338 consecutive male patients (aged ≤ 55 years) with premature ACS. The primary outcomes were all-cause mortality and major adverse cardiac and cerebrovascular events (MACCE). We compared the hazard ratios (HRs) in patients with and without normal weight central obesity using multivariable Cox proportional hazard models. All-cause mortality (16.8%) of patients with normal weight central obesity was much higher than those (7.1%) without normal weight central obesity (P = .008). The incidence of MACCE in patients with and without normal weight central obesity were 40.7 and 23.6% (P = .001), respectively. After multivariable adjustment, the risks of all-cause mortality and MACCE were significantly higher in patients with normal weight central obesity than those without normal weight central obesity (adjusted HR: 1.83; 95% confidence interval [CI]: 1.04-3.31; P = .004 and adjusted HR: 1.62; 95% CI: 1.18-2.27; P = .017, respectively). In conclusion, the risks of all-cause mortality and MACCE were significantly higher in male patients with premature ACS with normal weight central obesity than in those without normal weight central obesity.

Body mass index and risk of all-cause mortality with normoglycemia, impaired fasting glucose and prevalent diabetes: results from the Rural Chinese Cohort Study

BACKGROUND

Previous evidence of an association between body mass index (BMI) and mortality in patients with diabetes was inconsistent. The BMI-mortality association with normal fasting glucose (NFG), impaired fasting glucose (IFG) and prevalent diabetes is still unclear in the Chinese population.

METHODS

We analysed data for 17 252 adults from the Rural Chinese Cohort Study during 2007-2008 and followed for mortality during 2013-2014. Participants were classified with NFG, IFG and diabetes according to baseline measurement values of fasting glucose and self-reported diabetes. Multivariable Cox proportional hazard models were used to calculate HRs and 95% CIs across BMI categories by glycemic status.

RESULTS

During the 6-year follow-up, 1109 participants died (563/10 181 with NFG, 349/5572 with IFG and 197/1499 with diabetes). The BMI-mortality association was curvilinear, with low BMI (even in normal range) associated with increased mortality regardless of glycemic status. In adjusted Cox models, risk of mortality showed a decreasing trend with BMI≤18 kg/m², 18<BMI≤20 kg/m² and 20<BMI≤22 kg/m² vs 22<BMI≤24 kg/m²: HR 2.83 (95% CI 1.78 to 4.51), 2.05 (1.46 to 2.87) and 1.45 (1.10 to 1.90), respectively, for NFG; 2.53 (1.25 to 5.14), 1.36 (0.86 to 2.14) and 1.09 (0.76 to 1.57), respectively, for IFG; and 4.03 (1.42 to 11.50), 2.00 (1.05 to 3.80) and 1.52 (0.88 to 2.60), respectively, for diabetes. The risk of mortality was lower for patients with diabetes who were overweight or obese versus normal weight.

CONCLUSIONS

Low BMI was associated with increased mortality regardless of glycemic status. Future studies are needed to explain the 'obesity paradox' in patients with diabetes.

Abdominal Obesity Is Associated With an Increased Risk of All-Cause Mortality in Patients With HFpEF

BACKGROUND

There is a lack of studies that evaluate the association between abdominal obesity and subsequent outcomes in patients with heart failure with preserved ejection fraction (HFpEF).

OBJECTIVES

The present study aimed to assess the association between abdominal obesity and risk of all-cause mortality in patients with HFpEF.

METHODS

The present study used data from the TOPCAT (Treatment of Preserved Cardiac Function Heart Failure with an Aldosterone Antagonist) trial. The primary outcome was all-cause mortality. We analyzed and compared the hazard ratios (HRs) in patients with abdominal obesity and those without abdominal obesity using multivariable Cox proportional hazard models. Abdominal obesity was defined as a waist circumference of ≥102 cm in men and ≥88 cm in women.

RESULTS

The present study included 3,310 patients with HFpEF: 2,413 patients with abdominal obesity and 897 without abdominal obesity. The mean follow-up was 3.4 ± 1.7 years. During follow-up, 500 patients died. All-cause mortality rates in patients with and without abdominal obesity were 46.1 and 40.7 events per 1,000 person-years, respectively. After multivariable adjustment, the risk of all-cause mortality was significantly higher in patients with abdominal obesity than in those without abdominal obesity (adjusted HR: 1.52; 95% confidence interval [CI]: 1.16 to 1.99; p = 0.002). The risk of cardiovascular and noncardiovascular mortality was also significantly higher in patients with abdominal obesity than in those without abdominal obesity (adjusted HR: 1.50; 95% CI: 1.08 to 2.08; p = 0.01 and adjusted HR: 1.58; 95% CI: 1.00 to 2.51; p = 0.04, respectively).

CONCLUSIONS

The risk of all-cause mortality was significantly higher in patients with HFpEF with abdominal obesity than in those without abdominal obesity.

Body mass index and outcome after revascularization for symptomatic carotid artery stenosis

OBJECTIVE

To determine whether the obesity paradox exists in patients who undergo carotid artery stenting (CAS) or carotid endarterectomy (CEA) for symptomatic carotid artery stenosis.

METHODS

We combined individual patient data from 2 randomized trials (Endarterectomy vs Angioplasty in Patients with Symptomatic Severe Carotid Stenosis and Stent-Protected Angioplasty vs Carotid Endarterectomy) and 3 centers in a third trial (International Carotid Stenting Study). Baseline body mass index (BMI) was available for 1,969 patients and classified into 4 groups: <20, 20-<25, 25-<30, and ≥30 kg/m². Primary outcome was stroke or death, investigated separately for the periprocedural and postprocedural period (≤120 days/>120 days after randomization). This outcome was compared between different BMI strata in CAS and CEA patients separately, and in the total group. We performed intention-to-treat multivariable Cox regression analyses.

RESULTS

Median follow-up was 2.0 years. Stroke or death occurred in 159 patients in the periprocedural (cumulative risk 8.1%) and in 270 patients in the postprocedural period (rate 4.8/100 person-years). BMI did not affect periprocedural risk of stroke or death for patients assigned to CAS (p_trend = 0.39) or CEA (p_trend = 0.77) or for the total group (p_trend = 0.48). Within the total group, patients with BMI 25-<30 had lower postprocedural risk of stroke or death than patients with BMI 20-<25 (BMI 25-<30 vs BMI 20-<25; hazard ratio 0.72; 95% confidence interval 0.55-0.94).

CONCLUSIONS

BMI is not associated with periprocedural risk of stroke or death; however, BMI 25-<30 is associated with lower postprocedural risk than BMI 20-<25. These observations were similar for CAS and CEA.

The obesity paradox: is it really a paradox? Hypertension

This article is a narrative overview of the role of hypertension on the relationships between obesity, morbidity, and mortality. We used as sources MEDLINE/PubMed, CINAHL, EMBASE, and Cochrane Library, from inception to March 2016. Key words include overweight, obesity, visceral obesity, obesity paradox, and hypertension. In addition, we hand-searched references from the retrieved articles. This work is one of the works of the topical collection "Obesity Paradox". The positive association between overweight, obesity, and cardiovascular diseases is well established, though this relation is typically U shaped with an increased risk in low-weight subjects or even a beneficial effect of overweight and obesity, the so-called "obesity paradox". In addition, the relationship between obesity and arterial hypertension has been demonstrated in both children and adults by many epidemiological studies. Moreover, weight reduction is followed by a decrease in blood pressure in many patients and ameliorates the cardiovascular risk profile. Recent studies using more appropriate obesity indices raise some doubt about the real significance of obesity paradox and there are several studies that central obesity shows either no protective or even a worse effect. These observations raise the question: what kind of obesity is protective and what kind of obesity is harmful? The studies of obesity paradox suffer from several methodological limitations: most of these are retrospective analyses or were not specifically designed to study obesity paradox as a primary goal; a few studies have data on preceding unintentional weight loss and on some particular confounding variables. In conclusion, more prospective and accurate studies are necessary to better elucidate the clinical importance of obesity paradox. When weight loss is functional to reduce hypertension and cardiovascular risk, it should be encouraged, while an unintentional weight in a patient with chronic diseases may indicate an unfavorable course.

Obesity and stroke: Can we translate from rodents to patients?

Obesity is a risk factor for stroke and is consequently one of the most common co-morbidities found in patients. There is therefore an identified need to model co-morbidities preclinically to allow better translation from bench to bedside. In preclinical studies, both diet-induced and genetically obese rodents have worse stroke outcome, characterised by increased ischaemic damage and an altered inflammatory response. However, clinical studies have reported an 'obesity paradox' in stroke, characterised by reduced mortality and morbidity in obese patients. We discuss the potential reasons why the preclinical and clinical studies may not agree, and review the mechanisms identified in preclinical studies through which obesity may affects stroke outcome. We suggest inflammation plays a central role in this relationship, as obesity features increases in inflammatory mediators such as C-reactive protein and interleukin-6, and chronic inflammation has been linked to worse stroke risk and outcome.

Adjusting for reverse causation to estimate the effect of obesity on mortality after incident heart failure in the Atherosclerosis Risk in Communities (ARIC) study

OBJECTIVES:

The lower mortality rate of obese patients with heart failure (HF) has been partly attributed to reverse causation bias due to weight loss caused by disease. Using data about weight both before and after HF, this study aimed to adjust for reverse causation and examine the association of obesity both before and after HF with mortality.

METHODS:

Using the Atherosclerosis Risk in Communities (ARIC) study, 308 patients with data available from before and after the incidence of HF were included. Pre-morbid and post-morbid obesity were defined based on body mass index measurements at least three months before and after incident HF. The associations of pre-morbid and post-morbid obesity and weight change with survival after HF were evaluated using a Cox proportional hazard model.

RESULTS:

Pre-morbid obesity was associated with higher mortality (hazard ratio [HR], 1.61; 95% confidence interval [CI], 1.04 to 2.49) but post-morbid obesity was associated with increased survival (HR, 0.57; 95% CI, 0.37 to 0.88). Adjusting for weight change due to disease as a confounder of the obesity-mortality relationship resulted in the absence of any significant associations between post-morbid obesity and mortality.

CONCLUSIONS:

This study demonstrated that controlling for reverse causality by adjusting for the confounder of weight change may remove or reverse the protective effect of obesity on mortality among patients with incident HF.

The Obesity and Heart Failure Epidemics Among African Americans: Insights From the Jackson Heart Study

BACKGROUND

Higher rates of obesity and heart failure have been observed in African Americans, but associations with mortality are not well-described. We examined intermediate and long-term clinical implications of obesity in African Americans and associations between obesity and all-cause mortality, heart failure, and heart failure hospitalization.

METHODS AND RESULTS

We conducted a retrospective analysis of a community sample of 5292 African Americans participating in the Jackson Heart Study between September 2000 and January 2013. The main outcomes were associations between body mass index (BMI) and all-cause mortality at 9 years and heart failure hospitalization at 7 years using Cox proportional hazards models and interval development of heart failure (median 8 years' follow-up) using a modified Poisson model. At baseline, 1406 (27%) participants were obese and 1416 (27%) were morbidly obese. With increasing BMI, the cumulative incidence of mortality decreased (P= .007), whereas heart failure increased (P < .001). Heart failure hospitalization was more common among morbidly obese participants (9.0%; 95% confidence interval [CI] 7.6-11.7) than among normal-weight patients (6.3%; 95% CI 4.7-8.4). After risk adjustment, BMI was not associated with mortality. Each 1-point increase in BMI was associated with a 5% increase in the risk of heart failure (hazard ratio 1.05; 95% CI 1.03-1.06; P < .001) and the risk of heart failure hospitalization for BMI greater than 32 kg/m(2) (hazard ratio 1.05; 95% CI 1.03-1.07; P < .001).

CONCLUSIONS

Obesity and morbid obesity were common in a community sample of African Americans, and both were associated with increased heart failure and heart failure hospitalization.

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.

Body Mass Index, Outcomes, and Mortality Following Cardiac Surgery in Ontario, Canada

BACKGROUND

The "obesity paradox" reflects an observed relationship between obesity and decreased morbidity and mortality, suggesting improved health outcomes for obese individuals. Studies examining the relationship between high body mass index (BMI) and adverse outcomes after cardiac surgery have reported conflicting results.

METHODS AND RESULTS

The study population (N=78 762) was comprised of adult patients who had undergone first-time coronary artery bypass (CABG) or combined CABG/aortic valve replacement (AVR) surgery from April 1, 1998 to October 31, 2011 in Ontario (data from the Institute for Clinical Evaluative Sciences). Perioperative outcomes and 5-year mortality among pre-defined BMI (kg/m(2)) categories (underweight <20, normal weight 20 to 24.9, overweight 25 to 29.9, obese 30 to 34.9, morbidly obese >34.9) were compared using Bivariate analyses and Cox multivariate regression analysis to investigate multiple confounders on the relationship between BMI and adverse outcomes. A reverse J-shaped curve was found between BMI and mortality with their respective hazard ratios. Independent of confounding variables, 30-day, 1-year, and 5-year survival rates were highest for the obese group of patients (99.1% [95% Confidence Interval {CI}, 98.9 to 99.2], 97.6% [95% CI, 97.3 to 97.8], and 90.0% [95% CI, 89.5 to 90.5], respectively), and perioperative complications lowest. Underweight and morbidly obese patients had higher mortality and incidence of adverse outcomes.

CONCLUSIONS

Overweight and obese patients had lower mortality and adverse perioperative outcomes after cardiac surgery compared with normal weight, underweight, and morbidly obese patients. The "obesity paradox" was confirmed for overweight and moderately obese patients. This may impact health resource planning, shifting the focus to morbidly obese and underweight patients prior to, during, and after cardiac surgery.

Monocyte chemoattractant protein-1: a proinflammatory cytokine elevated in sarcopenic obesity

Objective

Sarcopenic obesity (SO) is associated with poorer physical outcomes and functional status in the older adult. A proinflammatory milieu associated with central obesity is postulated to enhance muscle catabolism. We set out to examine associations of the chemokine monocyte chemoattractant protein-1 (MCP-1) in groups of older adults, with sarcopenia, obesity, and the SO phenotypes.

Methods

A total of 143 community dwelling, well, older adults were recruited. Cross-sectional clinical data, physical performance, and muscle mass measurements were collected. Obesity and sarcopenia were defined using revised National Cholesterol Education Program (NCEP) obesity guidelines and those of the Asian Working Group for Sarcopenia. Serum levels of MCP-1 were measured by enzyme-linked immunosorbent assay (ELISA).

Results

In all, 25.2% of subjects were normal, 15.4% sarcopenic, 48.3% obese, and 11.2% were SO. The SO groups had the lowest appendicular lean mass, highest percentage body fat, and lowest performance scores on the Short Physical Performance Battery and grip strength. The MCP-1 levels were significantly different, with the highest levels found in SO participants (P<0.05).

Conclusion

Significantly raised MCP-1 levels in obese and SO subjects support the theory of chronic inflammation due to excess adiposity. Longitudinal studies will reveal whether SO represents a continuum of obesity causing accelerated sarcopenia and cardiovascular events, or the coexistence of two separate conditions with synergistic effects affecting functional performance.

Obesity paradox: conditioning on disease enhances biases in estimating the mortality risks of obesity

Supplemental Digital Content is available in the text.

Background:

Many studies have documented an obesity paradox—a survival advantage of being obese—in populations diagnosed with a medical condition. Whether obesity is causally associated with improved mortality in these conditions is unresolved.

Methods:

We develop the logic of collider bias as it pertains to the association between smoking and obesity in a diseased population. Data from the National Health and Nutrition Examination Survey (NHANES) are used to investigate this bias empirically among persons with diabetes and prediabetes (dysglycemia). We also use NHANES to investigate whether reverse causal pathways are more prominent among people with dysglycemia than in the source population. Cox regression analysis is used to examine the extent of the obesity paradox among those with dysglycemia. In the regression analysis, we explore interactions between obesity and smoking, and we implement a variety of data restrictions designed to reduce the extent of reverse causality.

Results:

We find an obesity paradox among persons with dysglycemia. In this population, the inverse association between obesity and smoking is much stronger than in the source population, and the extent of illness and weight loss is greater. The obesity paradox is absent among never-smokers. Among smokers, the paradox is eliminated through successive efforts to reduce the extent of reverse causality.

Conclusion:

Higher mortality among normal-weight people with dysglycemia is not causal but is rather a product of the closer inverse association between obesity and smoking in this subpopulation.

Adipose tissue, muscle, and function: potential mediators of associations between body weight and mortality in older adults with type 2 diabetes

OBJECTIVE

Studies in type 2 diabetes report both increased mortality for normal weight and no evidence of an obesity paradox. We aimed to examine whether adipose tissue, muscle size, and physical function, which are known to vary by weight, mediate associations between BMI and mortality.

RESEARCH DESIGN AND METHODS

The AGES-Reykjavik cohort comprised participants aged 66-96 years with diabetes defined by fasting glucose, medications, or self-report. BMI was determined from measured height and weight and classified as normal (18.5-24.9 kg/m(2), n = 117), overweight (25.0-29.9 kg/m(2), n = 293, referent group) or obese (≥30.0 kg/m(2), n = 227). Thigh muscle area and intermuscular, visceral, and subcutaneous adipose tissues were assessed with computed tomography. Function was assessed from gait speed and knee extensor strength. Hazard ratios (HRs) and 95% CIs were estimated by Cox proportional hazards regression adjusted for demographics and diabetes-related risk factors.

RESULTS

The median follow-up was 6.66 years, and there were 85, 59, and 44 deaths among normal weight, overweight, and obese participants, respectively. There was no mortality risk for obese participants and an increased risk among normal weight compared with overweight participants (HR 1.72 [95% CI 1.12-2.64]). Associations remained with adjustment for adipose tissues and knee extensor strength; however, mortality risk for normal weight was attenuated following adjustment for thigh muscle (HR 1.36 [95% CI 0.87-2.11]) and gait speed (HR 1.44 [95% CI 0.91-2.27]). Linear regression confirmed with bootstrapping indicated that thigh muscle size mediated 46% of the relationship between normal weight and mortality.

CONCLUSIONS

Normal weight participants had elevated mortality risk compared with overweight participants. This paradoxical association was mediated in part by muscle size.

Cardiorespiratory fitness and the paradoxical BMI-mortality risk association in male veterans

OBJECTIVE

To assess the effect of fitness status on the paradoxical body mass index (BMI)-mortality risk association.

PATIENTS AND METHODS

From February 1, 1986, through December 30, 2011, we assessed fitness and BMI in 18,033 male veterans (mean age, 58.4 ± 11.4 years) in 2 Veterans Affairs Medical centers. We established 3 fitness categories on the basis of peak metabolic equivalents achieved during an exercise test as well as 5 BMI categories. The primary outcome was all-cause mortality.

RESULTS

During the follow-up period (median, 10.8 years, comprising a total of 207,168 person-years), 5070 participants (28%) died. After adjusting for age, risk factors, muscle-wasting diseases, medications, and year of entry, mortality risk was higher for individuals with a BMI of 20.1 to 23.9 kg/m(2) (hazard ratio [HR], 1.21; 95% CI, 1.12-1.30) and 18.5 to 20.0 kg/m(2) (HR, 1.56; 95% CI, 1.37-1.77) than for those with a BMI of 24.0 to 27.9 kg/m(2); mortality risk was not increased for those with a BMI of 28.0 kg/m(2) or greater. When stratified by fitness, the trend was similar for low-fit and moderate-fit individuals. However, mortality risk was not increased for high-fit individuals across BMI categories. When fitness status was considered within each BMI category, mortality risk increased progressively with decreased fitness and was more pronounced for moderate-fit (HR, 2.52; 95% CI, 2.06-3.08) and low-fit (HR, 2.48; 95% CI, 2.0-3.06) individuals with a BMI of 18.5-20.0 kg/m(2). Mortality risk was not significantly increased for high-fit individuals (HR, 1.17; 95% CI, 0.78-1.78; P=.45).

CONCLUSION

A high mortality risk associated with low BMI levels was observed only in moderate-fit and low-fit individuals, and not in high-fit individuals. Thus, fitness greatly affects the paradoxical BMI-mortality risk association. Furthermore, our findings indicate that lower BMI levels do not increase the risk for premature death as long as they are associated with high fitness. Thus, the paradoxically higher mortality risk observed with lower body weight as represented by lower BMI is likely the result of unhealthy reduction in body weight and, perhaps most importantly, considerable loss of lean body mass.

The obesity paradox: understanding the effect of obesity on mortality among individuals with cardiovascular disease

OBJECTIVE

To discuss possible explanations for the obesity paradox and explore whether the paradox can be attributed to a form of selection bias known as collider stratification bias.

METHOD

The paper is divided into three parts. First, possible explanations for the obesity paradox are reviewed. Second, a simulated example is provided to describe collider stratification bias and how it could generate the obesity paradox. Finally, an example is provided using data from 17,636 participants in the US National and Nutrition Examination Survey (NHANES III). Generalized linear models were fit to assess the effect of obesity on mortality both in the general population and among individuals with diagnosed cardiovascular disease (CVD). Additionally, results from a bias analysis are presented.

RESULTS

In the general population, the adjusted risk ratio relating obesity and all-cause mortality was 1.24 (95% CI 1.11, 1.39). Adjusted risk ratios comparing obese and non-obese among individuals with and without CVD were 0.79 (95% CI 0.68, 0.91) and 1.30 (95% CI=1.12, 1.50), indicating that obesity has a protective association among individuals with CVD.

CONCLUSION

Results demonstrate that collider stratification bias is one plausible explanation for the obesity paradox. After conditioning on CVD status in the design or analysis, obesity can appear protective among individuals with CVD.

Body mass index, diabetes, and mortality in French women: explaining away a "paradox"

BACKGROUND

Obesity is associated with increased mortality in the general population but, paradoxically, with decreased mortality in persons with diabetes.

METHODS

Among 88,373 French women participating in the E3N-EPIC study who were free of diabetes in 1990, we estimated the hazard ratios (HRs) and 95% confidence intervals (CIs) of mortality for body mass index (BMI) levels by diabetes status.

RESULTS

During an average 16.7 years of follow-up, 2421 cases of diabetes were identified and 3750 deaths occurred. For overweight/obese versus normal-weight women, the HR of mortality was 1.42 (95% CI = 1.32-1.53) in women without diabetes and 0.69 (0.40-1.18) in women with incident diabetes. As BMI increased, mortality among women without diabetes increased and that among women with diabetes decreased.

CONCLUSIONS

We found the obesity "paradox" among women with and without incident diabetes in the same population. Selection bias may be a simple explanation for this "paradox."

Body-Mass Index and All-Cause Mortality in US Adults With and Without Diabetes

BACKGROUND

Previous studies found normal weight compared to overweight/obese adults with type 2 diabetes had a higher mortality risk, and body-mass index (BMI)-mortality studies do not typically account for baseline diabetes status.

OBJECTIVE

To determine if diabetes influences the BMI-mortality relationship.

DESIGN

Using a prospective study design, we analyzed data from a nationally representative sample of US adults participating in the National Health Interview Survey from 1997 to 2002, and followed for mortality through 2006.

PARTICIPANTS

Excluding those with heart disease or cancer, our final analytic sample included 74,710 (34,805 never smoker) adults.

MAIN MEASURES

BMI was calculated from self-reported height and weight. Diabetes status was based on self-reported diagnosis from a health professional. We used direct age standardization to calculate all-cause mortality rates and adjusted Cox models for all-cause mortality hazard ratios by BMI quintile; this was done separately for adults with diabetes and without diabetes.

KEY RESULTS

Among never smokers, mean age was 50.1 years and 43 % were men. Mean BMI was 27.4 kg/m(2), 26 % were obese, and 2,035 (5 %) reported diagnosed diabetes. After 9 years, there were 4,355 deaths (754 of 4,740 with diabetes; 3,601 of 69,970 without) among 74,710 participants, and 1,238 (247 of 2,035 with diabetes; 991 of 32,770 without) among 34,805 never smokers. We observed a qualitative interaction with diabetes on the BMI-mortality relationship (p = 0.002). Death rates were substantially higher among participants with diabetes compared to those without diabetes across all BMI quintiles. However, death rates in participants with diabetes fell with increasing BMI quintile, while rates followed a J-shaped curve among those without diabetes. In adjusted Cox models, BMI was positively associated with mortality in adults without diabetes, but inversely associated with mortality among participants with diabetes.

CONCLUSIONS

Mortality increased with increasing BMI in adults without diabetes, but decreased with increasing BMI among their counterparts with diabetes. Future studies need to be better designed to answer the question of whether normal weight adults with diabetes have a higher risk of mortality, by minimizing the possibility of reverse causation. Future studies should also account for prevalent diabetes in all investigations of the BMI-mortality relationship.

Comparing life expectancy and health-adjusted life expectancy by body mass index category in adult Canadians: a descriptive study

BACKGROUND

While many studies have examined differences between body mass index (BMI) categories in terms of mortality risk and health-related quality of life (HRQL), little is known about the effect of body weight on health expectancy. We examined life expectancy (LE), health-adjusted life expectancy (HALE), and proportion of LE spent in nonoptimal (or poor) health by BMI category for the Canadian adult population (age ≥ 20).

METHODS

Respondents to the National Population Health Survey (NPHS) were followed for mortality outcomes from 1994 to 2009. Our study population at baseline (n=12,478) was 20 to 100 years old with an average age of 47. LE was produced by building abridged life tables by sex and BMI category using data from the NPHS and the Canadian Chronic Disease Surveillance System. HALE was estimated using the Health Utilities Index from the Canadian Community Health Survey as a measure of HRQL. The contribution of HRQL to loss of healthy life years for each BMI category was also assessed using two methods: by calculating differences between LE and HALE proportional to LE and by using a decomposition technique to separate out mortality and HRQL contributions to loss of HALE.

RESULTS

At age 20, for both sexes, LE is significantly lower in the underweight and obesity class 2+ categories, but significantly higher in the overweight category when compared to normal weight (obesity class 1 was nonsignificant). HALE at age 20 follows these same associations and is significantly lower for class 1 obesity in women. Proportion of life spent in nonoptimal health and decomposition of HALE demonstrate progressively higher losses of healthy life associated with lowered HRQL for BMI categories in excess of normal weight.

CONCLUSIONS

Although being in the overweight category for adults may be associated with a gain in life expectancy as compared to normal weight adults, overweight individuals also experience a higher proportion of these years of life in poorer health. Due to the descriptive nature of this study, further research is needed to explore the causal mechanisms which explain these results, including the important differences we observed between sexes and within obesity subcategories.

Obesity and muscle strength as long-term determinants of all-cause mortality--a 33-year follow-up of the Mini-Finland Health Examination Survey

OBJECTIVE

To examine the independent and combined associations of obesity and muscle strength with mortality in adult men and women.

DESIGN

Follow-up study with 33 years of mortality follow-up.

SUBJECTS

A total of 3594 men and women aged 50-91 years at baseline with 3043 deaths during the follow-up.

MEASUREMENT

Body mass index (BMI) and handgrip strength were measured at baseline.

RESULTS

Based on Cox models adjusted for age, sex, education, smoking, alcohol use, physical activity and chronic conditions, baseline obesity (BMI ≥30 kg m(-2)) was associated with mortality among participants aged 50-69 years (hazard ratio (HR) 1.14, 95% confidence interval (CI), 1.01-1.28). Among participants aged 70 years and older, overweight and obesity were protective (HR 0.77, 95% CI, 0.66-0.89 and HR 0.76, 95% CI, 0.62-0.92). High handgrip strength was inversely associated with mortality among participants aged 50-69 (HR 0.89, 95% CI, 0.80-1.00) and 70 years and older (HR 0.78, 95% CI, 0.66-0.93). Compared to normal-weight participants with high handgrip strength, the highest mortality risk was observed among obese participants with low handgrip strength (HR 1.23, 95% CI, 1.04-1.46) in the 50-69 age group and among normal-weight participants with low handgrip strength (HR 1.30, 95% CI, 1.09-1.54) among participants aged 70+ years. In addition, in the old age group, overweight and obese participants with high handgrip strength had significantly lower mortality than normal-weight participants with high handgrip strength (HR 0.79, 95% CI, 0.67-0.92 and HR 0.77, 95% CI, 0.63-0.94).

CONCLUSION

Both obesity and low handgrip strength, independent of each other, predict the risk of death in adult men and women with additive pattern. The predictive value of obesity varies by age, whereas low muscle strength predicts mortality in all age groups aged>50 years and across all BMI categories. When promoting health among older adults, more attention should be paid to physical fitness in addition to body weight and adiposity.

The "obesity paradox," frailty, disability, and mortality in older men: a prospective, longitudinal cohort study

An inverse relationship between overweight and mortality (the "obesity paradox") is well documented, but there are scarce data on how body weight during the life course affects this relationship. In the Helsinki Businessmen Study, we examined the effect of weight trajectories on incident disability, frailty, and mortality by stratifying 1,114 men (mean age of 47 years in 1974) into the following 4 groups based on body mass index (weight (kg)/height (m)(2)) values measured twice, in 1974 and 2000: 1) constantly normal weight (n = 340, reference group); 2) constantly overweight (n = 495); 3) weight gain (n = 136); and 4) weight loss (n = 143). Twelve-year mortality rates (from 2000 to 2012) and frailty and mobility-related disability in late life were determined. Compared with constantly normal weight, weight loss was associated with disability (odds ratio (OR) = 2.4, 95% confidence interval (CI): 1.1, 4.9) and frailty (OR = 3.7, 95% CI: 1.3, 10.5) in late life. Constant overweight was associated with increased disability (OR = 1.9, 95% CI: 1.1, 3.2). Men with constantly normal weight had the fewest comorbidities in late life (P < 0.001). Higher 12-year mortality rates were observed both with weight loss (hazard ratio = 1.8, 95% CI: 1.3, 2.3) and with constant overweight (hazard ratio = 1.3, 95% CI: 1.03, 1.7). Those with constantly normal weight or weight gain had similar outcomes. We observed no obesity paradox in late life when earlier weight trajectories were taken into account.

The obesity paradox in heart failure patients with preserved versus reduced ejection fraction: a meta-analysis of individual patient data

BACKGROUND

In heart failure (HF), obesity, defined as body mass index (BMI) ≥30 kg m(-2), is paradoxically associated with higher survival rates compared with normal-weight patients (the 'obesity paradox'). We sought to determine if the obesity paradox differed by HF subtype (reduced ejection fraction (HF-REF) versus preserved ejection fraction (HF-PEF)).

PATIENTS AND METHODS

A sub-analysis of the MAGGIC meta-analysis of patient-level data from 14 HF studies was performed. Subjects were divided into five BMI groups: <22.5, 22.5-24.9 (referent), 25-29.9, 30-34.9 and ≥35 kg m(-2). Cox proportional hazards models adjusted for age, sex, aetiology (ischaemic or non-ischaemic), hypertension, diabetes and baseline blood pressure, stratified by study, were used to examine the independent association between BMI and 3-year total mortality. Analyses were conducted for the overall group and within HF-REF and HF-PEF groups.

RESULTS

BMI data were available for 23 967 subjects (mean age, 66.8 years; 32% women; 46% NYHA Class II; 50% Class III) and 5609 (23%) died by 3 years. Obese patients were younger, more likely to receive cardiovascular (CV) drug treatment, and had higher comorbidity burdens. Compared with BMI levels between 22.5 and 24.9 kg m(-2), the adjusted relative hazards for 3-year mortality in subjects with HF-REF were: hazard ratios (HR)=1.31 (95% confidence interval=1.15-1.50) for BMI <22.5, 0.85 (0.76-0.96) for BMI 25.0-29.9, 0.64 (0.55-0.74) for BMI 30.0-34.9 and 0.95 (0.78-1.15) for BMI ≥35. Corresponding adjusted HRs for those with HF-PEF were: 1.12 (95% confidence interval=0.80-1.57) for BMI <22.5, 0.74 (0.56-0.97) for BMI 25.0-29.9, 0.64 (0.46-0.88) for BMI 30.0-34.9 and 0.71 (0.49-1.05) for BMI ≥35.

CONCLUSIONS

In patients with chronic HF, the obesity paradox was present in both those with reduced and preserved ventricular systolic function. Mortality in both HF subtypes was U-shaped, with a nadir at 30.0-34.9 kg m(-2).