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

Liver at crossroads: unraveling the links between obesity, chronic liver diseases, and the mysterious obesity paradox

Obesity is a global health issue that is intricately linked to the development and progression of chronic liver disease (CLD). This bidirectional connection, coupled with the obesity paradox (OP), presents a management dilemma. The established influence of obesity on the development and progression of chronic liver disease (CLD) is surpassed by the liver's impact on the onset and advancement of obesity. Patients with CLD always experience increased energy expenditure, reduced appetite, and low protein synthesis, all of which might lead to weight loss. However, metabolic disturbances, hormonal imbalances, inflammatory signaling, immobility, drugs, and alterations in nutrient metabolism can contribute to the development and exacerbation of obesity. Despite the propagation of the OP concept, none of the guidelines has changed, recommending being overweight. Research bias and confounders might be the lifebuoy explanation. Additionally, overlooking the lethal morbidities of obesity for survival benefits full of suffering seems to be an illogical idea. Therefore, rather than endorsing an overweight status, emphasis should be placed on improving cardiorespiratory fitness and preventing sarcopenia to achieve better outcomes in patients with CLD. Accordingly, the complex interplay between obesity, CLD, and the concept of OP requires a sophisticated individualized management approach. Maximizing cardiorespiratory fitness and mitigating sarcopenia should be considered essential strategies for attaining the most favourable outcomes in patients with chronic liver disease (CLD).

DXA-Measured Abdominal Adipose Depots and Structural Brain Integrity in Postmenopausal Women

BACKGROUND

This study extends prior research from the MRI substudy of the Women's Health Initiative Memory Study (WHIMS-MRI) linking BMI to reduced brain atrophy and ischemic lesion load by examining DXA-based measurements of total body fat, total abdominal adipose tissue (TAT), abdominal visceral (VAT) and subcutaneous (SAT) adipose tissue, gynoid fat, and overall leg fat.

METHODS

The analytic sample consisted of 61 postmenopausal women (baseline mean age 69.5 [3.6]) enrolled in WHIMS-MRI who had undergone DXA scans. DXA scans were completed at years 0, 3, and 6, and MRI scans were conducted ~8 years after baseline. Adjusted linear regression models were used to analyze the association between adiposity averaged across the 3-time points and volumes of brain regions previously linked to dementia.

RESULTS

Higher levels of total body fat, TAT, VAT, SAT, gynoid, and overall leg fat were associated with larger hippocampal volume (β 0.02 [95% CI, 0.004-0.04]; 0.11 [0.02-0.21]; 0.26 [0.04-0.47]; 0.18 [0.03-0.33]; 0.18 [0.05-0.30]; 0.07 [0.009-0.12], respectively). No other significant associations were observed.

CONCLUSION

Higher levels of adiposity were positively associated with hippocampal volume. Additional research with larger sample sizes is needed to ascertain the significance of this association.

Oral resveratrol in adults with knee osteoarthritis: A randomized placebo-controlled trial (ARTHROL)

BACKGROUND

Resveratrol is a natural compound found in red wine. It has demonstrated anti-inflammatory properties in preclinical models. We compared the effect of oral resveratrol in a new patented formulation to oral placebo for individuals with painful knee osteoarthritis.

METHODS AND FINDINGS

ARTHROL was a double-blind, randomized, placebo-controlled, Phase 3 trial conducted in 3 tertiary care centers in France. We recruited adults who fulfilled the 1986 American College of Rheumatology criteria for knee osteoarthritis and reported a pain intensity score of at least 40 on an 11-point numeric rating scale (NRS) in 10-point increments (0, no pain, to 100, maximal pain). Participants were randomly assigned (1:1) by using a computer-generated randomization list with permuted blocks of variable size (2, 4, or 6) to receive oral resveratrol (40 mg [2 caplets] twice a day for 1 week, then 20 mg [1 caplet] twice a day; resveratrol group) or matched oral placebo (placebo group) for 6 months. The primary outcome was the mean change from baseline in knee pain on a self-administered 11-point pain NRS at 3 months. The trial was registered at ClinicalTrials.gov: (NCT02905799). Between October 20, 2017 and November 8, 2021, we assessed 649 individuals for eligibility, and from November 9, 2017, we recruited 142 (22%) participants (mean age 61.4 years [standard deviation (SD) 9.6] and 101 [71%] women); 71 (50%) were randomly assigned to the resveratrol group and 71 (50%) to the placebo group. At baseline, the mean knee pain score was 56.2/100 (SD 13.5). At 3 months, the mean reduction in knee pain was -15.7 (95% confidence interval (CI), -21.1 to -10.3) in the resveratrol group and -15.2 (95% CI, -20.5 to -9.8) in the placebo group (absolute difference -0.6 [95% CI, -8.0 to 6.9]; p = 0.88). Serious adverse events (not related to the interventions) occurred in 3 (4%) in the resveratrol group and 2 (3%) in the placebo group. Our study has limitations in that it was underpowered and the effect size, estimated to be 0.55, was optimistically estimated.

CONCLUSIONS

In this study, we observed that compared with placebo, oral resveratrol did not reduce knee pain in people with painful knee osteoarthritis.

TRIAL REGISTRATION

ClinicalTrials.gov ID: NCT02905799.

Athletic Injury Research: Frameworks, Models and the Need for Causal Knowledge

Within applied sports science and medicine research, many challenges hinder the establishment and detailed understanding of athletic injury causality as well as the development and implementation of appropriate athletic injury prevention strategies. Applied research efforts are faced with a lack of variable control, while the capacity to compensate for this lack of control through the application of randomised controlled trials is often confronted by a number of obstacles relating to ethical or practical constraints. Such difficulties have led to a large reliance upon observational research to guide applied practice in this area. However, the reliance upon observational research, in conjunction with the general absence of supporting causal inference tools and structures, has hindered both the acquisition of causal knowledge in relation to athletic injury and the development of appropriate injury prevention strategies. Indeed, much of athletic injury research functions on a (causal) model-blind observational approach primarily driven by the existence and availability of various technologies and data, with little regard for how these technologies and their associated metrics can conceptually relate to athletic injury causality and mechanisms. In this article, a potential solution to these issues is proposed and a new model for investigating athletic injury aetiology and mechanisms, and for developing and evaluating injury prevention strategies, is presented. This solution is centred on the construction and utilisation of various causal diagrams, such as frameworks, models and causal directed acyclic graphs (DAGs), to help guide athletic injury research and prevention efforts. This approach will alleviate many of the challenges facing athletic injury research by facilitating the investigation of specific causal links, mechanisms and assumptions with appropriate scientific methods, aiding the translation of lab-based research into the applied sporting world, and guiding causal inferences from applied research efforts by establishing appropriate supporting causal structures. Further, this approach will also help guide the development and adoption of both relevant metrics (and technologies) and injury prevention strategies, as well as encourage the construction of appropriate theoretical and conceptual foundations prior to the commencement of applied injury research studies. This will help minimise the risk of resource wastage, data fishing, p-hacking and hypothesising after the results are known (HARK-ing) in athletic injury research.

Prevalence of prediabetes by the fasting plasma glucose and HbA1c screening criteria among the children and adolescents of Shenzhen, China

Background

Prediabetes is associated with an increased risk of cardiovascular diseases and all-cause mortality. Rare research in China has evaluated the prevalence of prediabetes among children and adolescents using the HbA1c criterion or the combined FPG-or-HbA1c diagnostic criterion, and researchers paid no attention to the distributions of blood glucose in Shenzhen, especially for juveniles.

Methods

We conducted a school-based cross-sectional study based on the first-year students from 17 primary, middle, and high schools. Prediabetes was defined as FPG of 5.6-6.9 mmol/L or HbA1c of 5.7%-6.4%. The crude and standardized prevalence of prediabetes with 95% confidence interval (95% CI) was estimated.

Results

A total of 7519 participants, aged 6 to 17 years, were included. For all subjects, the crude prevalence (95% CI) of prediabetes was 1.49% (1.21-1.77), 8.72% (8.08-9.36), and 9.80% (9.13-10.47) by the FPG-only, HbA1c-only, and FPG-or-HbA1c criteria, respectively. Based on the 2010 Shenzhen census population, the standardized prevalence was 1.56% (males 1.85%, females 1.19%), 11.05% (males 11.47%, females 10.53%), and 12.19% (males 13.01%, females 11.15%) by the corresponding criteria. The proportion of prediabetes was higher for males than females, and the prevalence decreased with grade for males but increased for females. The association of BMI and prediabetes was U-shaped curve, indicating higher rates of prediabetes for underweight and obesity people.

Conclusion

The blood glucose status of children and adolescents in Shenzhen is worrisome, and the early detection and management of prediabetes are imperative.

Increased TG Levels and HOMA-IR Score Are Associated With a High Risk of Prediabetes: A Prospective Study

This study aimed to determine the association of blood lipid and insulin levels with the development of prediabetes. In this prospective cohort study, we collected and analyzed data related to demographic characteristics, lipid profiles, and insulin parameters at baseline (2008-2012) and at follow-up (2019-2020). A total of 1205 participants were included. The study found that maintained or elevated Homeostatic Model Assessment for Insulin Resistance (HOMO-IR) score and elevated triglyceride (TG) levels from baseline to follow-up were associated with an increased risk of prediabetes. However, the interaction between blood lipids and insulin had no significant effect on the risk of prediabetes. Our findings indicate that elevated TG or HOMA-IR levels are associated with an increased risk of prediabetes. These findings emphasize the need to formulate initiatives that can help reduce dyslipidemia to prevent the onset of prediabetes and diabetes.

Association of body indices and risk of mortality in patients with type 2 diabetes

INTRODUCTION

A body shape index (ABSI) is independently associated with mortality in general population, but studies on the predictability of ABSI in the risk of mortality in patients with type 2 diabetes (T2D) are limited. We aimed to examine the independent and joint association of ABSI, body mass index (BMI), waist circumference (WC), waist-to-hip ratio (WHR), waist-to-height ratio (WHtR), and body roundness index (BRI) with mortality in patients with T2D.

RESEARCH DESIGN AND METHODS

The study included 11 872 patients (46.5% women) aged 30 years and older and who took part in diabetes care management program of a medical center in Taiwan. Body indices were evaluated by anthropometric measurements at baseline between 2001 and 2016, and their death status was followed up through 2021. Multivariate Cox regression models were used to assess the effect of body indices on mortality.

RESULTS

During a mean follow-up of 10.2 years, 560 cardiovascular disease (CVD) deaths and 3043 deaths were recorded. For ABSI, WC, WHR, WHtR and BRI, all-cause mortality rates were statistically significantly greater in Q4 versus Q2. For BMI and WHtR, all-cause mortality rates were also statistically significantly greater in Q1 versus Q2. The combination of BMI and ABSI exhibited a superiority in identifying risks of all-cause mortality and CVD mortality (HRs: 1.45 and 1.37, both p<0.01).

CONCLUSIONS

Combined use of ABSI and BMI can contribute to the significant explanation of the variation in death risk in comparison with the independent use of BMI or other indices.

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.

Smoking and Risk of Prostate Cancer and Prostate Cancer Death: A Pooled Study

BACKGROUND

Prospective and detailed investigations of smoking and prostate cancer (PCa) risk and death are lacking.

OBJECTIVE

To investigate prediagnosis smoking habit (status, intensity, duration, and cessation) as a risk factor, on its own and combined with body mass index (BMI), for PCa incidence and death.

DESIGN, SETTING, AND PARTICIPANTS

We included 351448 men with smoking information from five Swedish cohorts.

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS

We used Cox regression to calculate hazard ratios (HRs) and confidence intervals (CIs) for PCa incidence (n = 24731) and death (n = 4322).

RESULTS AND LIMITATIONS

Smoking was associated with a lower risk of any PCa (HR 0.89, 95% CI 0.86-0.92), which was most pronounced for low-risk PCa (HR 0.74, 95% CI 0.69-0.79) and was restricted to PCa cases diagnosed in the prostate-specific antigen (PSA) era. Smoking was associated with a higher risk of PCa death in the full cohort (HR 1.10, 95% CI 1.02-1.18) and in case-only analysis adjusted for clinical characteristics (HR 1.20, 95% CI 1.11-1.31), which was a consistent finding across case groups (p = 0.8 for heterogeneity). Associations by smoking intensity and, to lesser degree, smoking duration and cessation, supported the associations for smoking status. Smoking in combination with obesity (BMI ≥30 kg/m²) further decreased the risk of low-risk PCa incidence (HR 0.40, 95% CI 0.30-0.53 compared to never smokers with BMI <25 kg/m²) and further increased the risk of PCa death (HR 1.49, 95% CI 1.21-1.84). A limitation of the study is that only a subgroup of men had information on smoking habit around the time of their PCa diagnosis.

CONCLUSIONS

The lower PCa risk for smokers in the PSA era, particularly for low-risk PCa, can probably be attributed to low uptake of PSA testing by smokers. Poor survival for smokers, particularly obese smokers, requires further study to clarify the underlying causes and the preventive potential of smoking intervention for PCa death.

PATIENT SUMMARY

Smokers have a higher risk of dying from prostate cancer, which further increases with obesity.

The obesity paradox is mostly driven by decreased noncardiovascular disease mortality in the oldest old in China: a 20-year prospective cohort study

National and international recommendations of healthy body mass index (BMI) are primarily based on evidence in young and middle-aged populations, with an insufficient representation of the oldest old (aged ≥80 years). Here, we report associations between BMI and mortality risk in 27,026 community-dwelling oldest old (mean age, 92.7 ± 7.5 years) in China from 1998 to 2018. Nonlinear curves showed reverse J-shaped associations of BMI with cardiovascular disease (CVD), non-CVD and all-cause mortality, with a monotonic decreased risk up to BMIs in the overweight and mild obesity range and flat hazard ratios thereafter. Compared to normal weight, overweight and obesity were significantly associated with decreased non-CVD and all-cause mortality, but not with CVD mortality. Similar associations were found for waist circumference. Our results lend support to the notion that optimal BMI in the oldest old may be around the overweight or mild obesity range and challenge the application of international and national guidelines on optimal BMI in this age group.

Determinants of metabolic syndrome and type 2 diabetes in the absence of obesity: The Jackson Heart Study

Context

Multiple studies suggest that adults who were normal weight at diabetes diagnosis are at higher risk for all-cause mortality than those who had overweight or obesity at diagnosis.

Objective

While obesity is a known risk factor for cardiometabolic disease, differences in body fat distribution in those without obesity are understudied, especially in African Americans.

Methods

In 1005 participants of the Jackson Heart Study, without cardiovascular disease at baseline, we used logistic regression to investigate the longitudinal association of body fat distribution by CT scan with metabolic syndrome (MetS) or type 2 diabetes (T2D). We used the harmonized International Diabetes Federation criteria to define MetS. We included only normal weight or overweight participants (BMI: 18.5 to < 30.0 kg/m²). We created separate models for MetS and T2D adjusted for a standard set of covariates. We excluded participants with prevalent MetS or T2D, respectively in sensitivity.

Results

Higher visceral fat, subcutaneous fat, BMI, and insulin resistance (HOMA-IR) were significantly associated with MetS and T2D after adjustment. Visceral fat was strongly associated with both outcomes (MetS OR = 2.07 [1.66-2.68]; T2D OR = 1.51 [1.21-1.88]), and the association for MetS persisted in the normal weight only group. Estimates were robust to sensitivity analysis and were only modestly mediated by insulin resistance. Physical activity was not associated with MetS or T2D.

Conclusion

Visceral fat is strongly associated with developing MetS, even in normal weight individuals, suggesting that excess visceral fat plays a role in cardiometabolic risk beyond that of overall adiposity and obesity in African Americans.

Revisiting the Obesity Paradox in Health Care Expenditures Among Adults With Diabetes

Recent studies of diabetes suggest an obesity paradox: mortality risk increases with weight in people without diabetes but decreases with weight in people with diabetes. A recent study also reports the paradox more generally with health care utilization. Whether this paradox in health care utilization and spending is causal or instead the result of empirical biases and confounding factors has yet to be examined in detail. This study set out to examine changes in the relationship between BMI and health care expenditures in populations with versus without diabetes, controlling for confounding risk factors. It found that the obesity paradox does not exist and is the result of statistical biases such as confounding and reverse causation. Obesity is not cost-saving for people with diabetes. Thus, insurers and physicians should renew efforts to prevent obesity in people with diabetes.

Explaining the obesity paradox in healthcare utilization among people with type 2 diabetes

Background

Several studies of diabetes suggest an obesity paradox: persons without diabetes have an increased risk of death due to obesity, whereas obesity decreases the risk of death for people with diabetes. A recent study finds the same obesity paradox with the number of healthcare visits. Whether empirical biases and confounding lead to this paradox is yet to be determined.

Objective

To examine changes in the relationship between BMI and number of visits in diabetic vs nondiabetic populations, controlling for confounding risk factors.

Methods

Using adults in the nationally representative Medical Expenditure Panel Survey (MEPS) from 2008 to 2016, N = 210,317, we examine the proposed relationship using six measures of healthcare visits with zero-inflated negative binomial regressions controlling for age, gender, race/ethnicity, income, education, region, health insurance, chronic conditions, and smoking. We excluded persons with type 1 diabetes and gestational diabetes.

Results

We find an obesity paradox among people with diabetes for three measures. That is, relative to people without diabetes, normal weight people with diabetes have more emergency room visits, inpatient, and office-based physician visits than do the obese with diabetes. However, we do not find an obesity paradox in any of the six measures once we exclude smokers and persons ever diagnosed with cancer or cardiovascular disease.

Conclusion

The obesity paradox does not exist at the utilization level and is due to the presence of statistical biases such as confounding and reverse causation. Physicians should continue to focus on efforts to prevent obesity in patients with diabetes.

The obesity paradox and diabetes

BACKGROUND

Obesity has been proven to be a risk factor for type 2 diabetes mellitus (T2DM) through numerous pathogenetic mechanisms. Unexpectedly, some studies suggest that subjects with overweight/obesity and T2DM have better clinical outcome than their normal weight peers. This finding is described as "obesity paradox" and calls into question the importance of weight loss in this specific population.

OBJECTIVE

This article is a narrative overview on the obesity and type 2 diabetes mellitus, particularly regarding the obesity paradox in T2DM patients.

METHODS

We used as sources MEDLINE/PubMed, CINAHL, EMBASE, and Cochrane Library, from inception to March 2020; we chose 30 relevant papers regarding the association of obesity with clinical outcome and mortality of patients affected by T2DM.

RESULTS

Many studies report that in patients with T2DM, overweight and obesity are associated with a better prognosis than underweight or normal weight, suggesting the presence of an obesity paradox. However, these studies have numerous limitations due to their mainly retrospective nature and to numerous confounding factors, such as associated pathologies, antidiabetic treatments, smoking habit, lack of data about distribution of body fat or weight history.

CONCLUSION

Literature data regarding the phenomenon of obesity paradox in T2DM patients are controversial due to the several limitations of the studies; therefore in the management of patients with overweight/obesity and T2DM is recommended referring to the established guidelines, which indicate diet and physical activity as the cornerstone of the treatment.

LEVEL OF EVIDENCE

Level V: narrative review.

Association between blood pressure and BMI with bladder cancer risk and mortality in 340,000 men in three Swedish cohorts

BACKGROUND

The relation between obesity, blood pressure (BP) and bladder cancer (BC) risk and mortality remains unclear, partially due to potential confounding by smoking, the strongest risk factor for BC, and not accounting for tumor stage and grade in such studies. We investigated body mass index (BMI) and BP in relation to BC risk by stage and grade, and BC-specific mortality, including separately among never-smokers aimed at minimizing confounding by smoking.

METHODS

We analyzed 338,910 men from three Swedish cohorts, with 4895 incident BC's (940 among never-smokers) during follow-up. Cox regression was used to calculate hazard ratios (HR) and 95% confidence intervals adjusted for smoking status. HRs for BMI and BP were corrected for their regression dilution ratios, calculated from 280,456 individuals with 758,641 observations.

RESULTS

Body mass index was positively associated with non-muscle invasive BC (NMIBC, HR per 5 kg/m2 , 1.10 [1.02-1.19]) and NMIBC grade 3 (HR 1.17 [1.01-1.34]) in the full cohort, with similar effect sizes, albeit non-significant, among never-smokers. Systolic BP was positively associated with muscle-invasive BC (MIBC, HR per 10 mmHg, 1.25 [1.00-1.55]) and BC-specific mortality (HR 1.10 [1.01-1.20]) among never-smokers, with weaker and non-significant associations in the full cohort.

CONCLUSIONS

In an analyses of BMI, BP and BC risk by stage and grade among men, we found modest positive associations between BMI and NMIBC and NMIBC grade 3. SBP was positively associated with MIBC and BC-specific mortality in an analysis of never-smokers, which may reflect the association, un-confounded by smoking, also in a broader population.

Height, body mass index and prostate cancer risk and mortality by way of detection and cancer risk category

Obesity is a risk factor for advanced, but not localised, prostate cancer (PCa), and for poor prognosis. However, the detection of localised PCa through asymptomatic screening might influence these associations. We investigated height and body mass index (BMI) among 431 902 men in five Swedish cohorts in relation to PCa risk, according to cancer risk category and detection mode, and PCa-specific mortality using Cox regression. Statistical tests were two-sided. Height was positively associated with localised intermediate-risk PCa (HR per 5 cm, 1.03, 95% CI 1.01-1.05), while overweight and obesity were negatively associated with localised low- and intermediate-risk PCa (HRs per 5 kg/m² , 0.86, 95% CI 0.81-0.90, and 0.92, 95% CI 0.88-0.97). However, these associations were partially driven by PCa's detected by asymptomatic screening and, for height, also by symptoms unrelated to PCa. The HR of localised PCa's, per 5 kg/m² , was 0.88, 95% CI 0.83 to 0.92 for screen-detected PCa's and 0.96, 95% CI 0.90 to 1.01 for PCa's detected through lower urinary tract symptoms. BMI was positively associated with PCa-specific mortality in the full population and in case-only analysis of each PCa risk category (HRs per 5 kg/m² , 1.11-1.22, P for heterogeneity = .14). More active health-seeking behaviour among tall and normal-weight men may partially explain their higher risk of localised PCa. The higher PCa-specific mortality among obese men across all PCa risk categories in our study suggests obesity as a potential target to improve the prognosis of obese PCa patients.

Is the Obesity Paradox in Type 2 Diabetes Due to Artefacts of Biases? An Analysis of Pooled Cohort Data from the Heinz Nixdorf Recall Study and the Study of Health in Pomerania

AIMS/HYPOTHESIS

There is controversy on whether an obesity paradox exists in type 2 diabetes, ie, that mortality is lowest in overweight or obesity. We examined the role of potential biases in the obesity paradox.

METHODS

From two regional population-based German cohort studies - the Heinz Nixdorf Recall Study and the Study of Health in Pomerania (baseline examinations 2000-2003/1997-2001) - 1187 persons with diabetes at baseline were included (mean age 62.6 years, 60.9% males). Diabetes was ascertained by self-report of physician's diagnosis, antidiabetic medication, fasting/random glucose or haemoglobin A1c. Mortality data were assessed for up to 17.7 years. We used restricted cubic splines and Cox regression models to assess associations between body mass index (BMI) and mortality. Sensitivity analyses addressed, inter alia, exclusion of early death cases, of persons with cancer, kidney disease or with history of cardiovascular diseases, and of ever smokers. Furthermore, we examined the role of treatment bias and collider bias for the obesity paradox.

RESULTS

In spline models, mortality risk was lowest for BMI at about 31 kg/m2. Sensitivity analyses carried out one after another had hardly any impact on this result. In our cohort, persons with diabetes and BMI ≥30 kg/m2 did not have better treatment than non-obese patients, and we found that collider bias played only a minor role in the obesity paradox.

CONCLUSION

In a cohort of 1187 persons with diabetes, mortality risk was lowest in persons with moderate obesity. We cannot explain this result by a variety of sensitivity analyses.

Lifestyle and Progression to Type 2 Diabetes in a Cohort of Workers with Prediabetes

Background: People with prediabetes have an increased risk of developing type 2 diabetes (T2D). Few studies have evaluated the influence of lifestyle factors on the risk of progression to diabetes and reversion to normoglycemia. The aim of this study was to determine the incidence of T2D in a large cohort of workers with prediabetes, and to evaluate the influence of sociodemographic, clinical, metabolic, and lifestyle factors that affect the persistence of prediabetes and the progression to T2D. Methods: A cohort study of 27,844 adult workers (aged 20 to 65 years) from Spain who had prediabetes based on an occupational medical examination from 2012 to 2013. Prediabetes was defined as fasting plasma glucose (FPG) between 100 and 125 mg/dL. At the baseline evaluation, sociodemographic, anthropometric, metabolic, and lifestyle data were collected. At the 5-year follow-up, incident T2D was defined as an FPG of at least 126 mg/dL or initiation of an antidiabetic medication. Results: Among 235,995 initially screened workers, the prevalence of T2D was 14.19% (95% confidence interval (CI) 14.05 to 14.33) and the prevalence of prediabetes was 11.85% (95% CI 11.71 to 11.99). Follow-up data were available for 23,293 individuals with prediabetes. Among them, 36.08% (95% CI 35.46 to 36.70) returned to normoglycemia, 40.92% (95% CI 40.29 to 41.55) had persistent prediabetes, and 23.00% (95% CI 22.46 to 23.54) progressed to T2D. The risk for persistence of prediabetes and for progression to T2D increased with age, body mass index (BMI), triglyceride level, and less than 150 min/week of physical activity. An HbA1c level of 6% or greater was the strongest individual predictor of progression to T2D. Conclusions: Physical activity, diet, smoking, and BMI are modifiable factors that are associated with the persistence of prediabetes and the progression to T2D. The workplace is a feasible setting for the early detection of prediabetes and the promotion of lifestyles that can prevent progression to T2D.

[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.

Positive family history of cardiovascular disease and long-term outcomes after coronary artery bypass grafting: a genetic paradox?

OBJECTIVES

Parental cardiovascular disease (CVD) is a known risk factor for premature CVD. It is unknown whether a positive family history (PFH) affects outcomes after coronary artery bypass grafting (CABG).

METHODS

Data come from a retrospective longitudinal study of CABG patients consecutively recruited from 2001 to 2018 (n = 5389). From this study, 2535 patients with premature CVD undergoing CABG under the age of 60 years and information on parental CVD were identified. The Framingham offspring study criteria were used to identify PFH of CVD. Multivariable Cox proportional hazards regression models were used to assess the effect of PFH on overall and major adverse cardiovascular and cerebrovascular event-free survival.

RESULTS

A total of 273 deaths and 428 major adverse cardiovascular and cerebrovascular events occurred during follow-up. PFH of CVD was found in 54.2% of patients (n = 1375). Within these patients, 66.1% had a father who experienced a premature cardiovascular event (n = 909), 27.8% a mother (n = 382) and 6.1% both a mother and a father (n = 84). In the majority of cases, the patient's parent had experienced a cardiac event (85.9%, n = 1181) and 14.1% of patients with PFH reported parental stroke (n = 194). Following CABG, PFH was associated with improved overall [adjusted hazards ratio (HR) 0.67, 95% confidence interval (CI) 0.50-0.90; P = 0.008] and major adverse cardiovascular and cerebrovascular event-free survival (adjusted HR 0.73, 95% CI 0.68-0.89; P = 0.01). Among the covariates adjusted for age, diabetes, renal insufficiency, peripheral arterial disease, ejection fraction, previous cerebrovascular events and previous mediastinal radiation were all associated with poorer outcomes.

CONCLUSIONS

Although it is well established that a PFH increases the risk of requiring CABG at younger ages, this study shows that, paradoxically, PFH is also protective regarding long-term outcomes.

REGISTRATION NUMBER LOCAL IRB

UN4232 297/4.3 (retrospective study).

Demystifying Smoker's Paradox: A Propensity Score-Weighted Analysis in Patients Hospitalized With Acute Heart Failure

Background Smoker's paradox has been observed with several vascular disorders, yet there are limited data in patients with acute heart failure (HF). We examined the effects of smoking in patients with acute HF using data from a large multicenter registry. The objective was to determine if the design and analytic approach could explain the smoker's paradox in acute HF mortality. Methods and Results The data were sourced from the acute HF registry (Gulf CARE [Gulf Acute Heart Failure Registry]), a multicenter registry that recruited patients over 10 months admitted with a diagnosis of acute HF from 47 hospitals in 7 Middle Eastern countries. The association between smoking and mortality (in hospital) was examined using covariate adjustment, making use of mortality risk factors. A parallel analysis was performed using covariate balancing through propensity scores. Of 5005 patients hospitalized with acute HF, 1103 (22%) were current smokers. The in-hospital mortality rates were significantly lower in current smoker's before (odds ratio, 0.71; 95% CI, 0.52-0.96) and more so after (odds ratio, 0.47; 95% CI, 0.31-0.70) covariate adjustment. With the propensity score-derived covariate balance, the smoking effect became much less certain (odds ratio, 0.63; 95% CI, 0.36-1.11). Conclusions The current study illustrates the fact that the smoker's paradox is likely to be a result of residual confounding as covariate adjustment may not resolve this if there are many competing prognostic confounders. In this situation, propensity score methods for covariate balancing seem preferable. Clinical Trial Registration URL: https://www.clinicaltrials.gov/. Unique identifier: NCT01467973.

Race and Mortality in CKD and Dialysis: Findings From the Chronic Renal Insufficiency Cohort (CRIC) Study

RATIONALE & OBJECTIVES

Few studies have investigated racial disparities in survival among dialysis patients in a manner that considers risk factors and mortality during the phase of kidney disease before maintenance dialysis. Our objective was to explore racial variations in survival among dialysis patients and relate them to racial differences in comorbid conditions and rates of death in the setting of kidney disease not yet requiring dialysis therapy.

STUDY DESIGN

Retrospective cohort study.

SETTINGS & PARTICIPANTS

3,288 black and white participants in the Chronic Renal Insufficiency Cohort (CRIC), none of whom were receiving dialysis at enrollment.

EXPOSURE

Race.

OUTCOME

Mortality.

ANALYTIC APPROACH

Cox proportional hazards regression was used to examine the association between race and mortality starting at: (1) time of dialysis initiation and (2) entry into the CRIC.

RESULTS

During 7.1 years of median follow-up, 678 CRIC participants started dialysis. Starting from the time of dialysis initiation, blacks had lower risk for death (unadjusted HR, 0.67; 95% CI, 0.51-0.87) compared with whites. Starting from baseline CRIC enrollment, the strength of the association between some risk factors and dialysis was notably stronger for whites than blacks. For example, the HR for dialysis onset in the presence (vs absence) of heart failure at CRIC enrollment was 1.30 (95% CI, 1.01-1.68) for blacks versus 2.78 (95% CI, 1.90-4.50) for whites, suggesting differential severity of these risk factors by race. When we included deaths occurring both before and after dialysis, risk for death was higher among blacks (vs whites) starting from CRIC enrollment (HR, 1.41; 95% CI, 1.22-1.64), but this finding was attenuated in adjusted models (HR, 1.08; 95% CI, 0.91-1.28).

LIMITATIONS

Residual confounding.

CONCLUSIONS

The apparent survival advantage among blacks over whites treated with dialysis may be attributed to selected transition of a subset of whites with more severe comorbid conditions onto dialysis.

A Multicenter Large-Scale Retrospective Analysis of the Correlation between Body Mass Index and All-Cause Mortality in Patients with Type 2 diabetes Mellitus: A Seven-Year Real-World Study

Aims: To investigate the association between body mass index (BMI) and all-cause mortality in patients with type 2 diabetes mellitus (T2DM) and to determine any sex-specific differences in this association. Methods: We retrospectively enrolled patients with T2DM and investigated the annual death data for seven years starting from 2010. All-cause mortality was calculated using Life Tables analysis. Multivariate Cox proportional hazards analysis was performed to identify the association between BMI and mortality. Results: During a mean survey period of 7.33 ± 1.42 years (X± SD), 996 of the 17259 patients enrolled died, resulting in an all-cause mortality rate of 5.77%, with no significant difference between women and men (6.04% vs. 5.56%; x² = 1.766, P = 0.184). The top three causes of death were ischemic heart disease, cerebrovascular disease, and chronic kidney failure. A total of 87, 266, 332, and 311 patients with a BMI of <18.5, 18.5-23.99, 24.0-27.99, and ≥28.0 kg/m², respectively, died, with the corresponding mortality rate calculated at 15.45%, 3.30%, 5.80%, and 10.70%, respectively. The BMI value associated with the highest all-cause mortality was <18.5 kg/m², but this association was only significant in women aged <50 years (HR: 3.12; 95% CI, 1.62-4.34; P < 0.001). Conclusions: In patients with T2DM, a low BMI in women aged <50 years predicted high all-cause mortality.

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.

Exploring the association between BMI and mortality in Australian women and men with and without diabetes: the AusDiab study

AIMS/HYPOTHESIS

There is conflicting evidence about the obesity paradox-the counterintuitive survival advantage of obesity among certain subpopulations of individuals with chronic conditions. It is believed that results supporting the obesity paradox are due to methodological flaws, such as collider bias. The aim of this study was to examine the association between obesity and mortality in Australian men and women. In addition, we explored whether obesity would appear to be protective if the analysis was restricted to a subpopulation with disease, and to discuss the potential role of collider bias in producing such a result.

METHODS

The examined cohort included 10,575 Australian adults (4844 men and 5731 women) aged 25-91 years who were recruited for the AusDiab baseline survey in 1999 and followed-up through 2014. The main predictor variable was BMI categorised as normal weight (18.5 to <25 kg/m²), overweight (25 to <30 kg/m²) and obese (≥30 kg/m²), and the outcome of interest was all-cause mortality. Hazard ratios were estimated from Cox proportional hazards regression models in the entire cohort and then in subpopulations with and without diabetes.

RESULTS

A total of 1477 deaths occurred during 145,384 person-years (median 14.6 years) of follow-up. Mortality was higher in obese than in normal-weight individuals for the full population (HR 1.18; 95% CI 1.05, 1.32). When an interaction between diabetes status and BMI category was added to the model, there was no evidence of an interaction between BMI and diabetes status (p = 0.92). When participants with and without diabetes were analysed separately, there was no evidence of an association between obesity and mortality in those with diabetes (HR 0.91; 95% CI 0.62, 1.33).

CONCLUSIONS/INTERPRETATION

In the entire AusDiab cohort, we found a significantly higher mortality among obese participants as compared with their normal-weight counterparts. We found no difference in the obesity-mortality association between individuals with and without diabetes.

Triglycerides Paradox Among the Oldest Old: "The Lower the Better?"

OBJECTIVES

Currently, most treatment guidelines suggest lowering hypertriglyceridemia of any severity, even in elderly individuals. However associations of serum triglycerides (TGs) with adverse health and mortality risk decrease with age, it remains unclear among the oldest old (aged 80 years and older). The study was to investigate the relationship of serum TG concentrations with cognitive function, activities of daily living (ADLs), frailty, and mortality among the oldest old in a prospective cohort study.

DESIGN

Longitudinal prospective cohort study.

SETTING

Community-based setting in longevity areas in China.

PARTICIPANTS

A total of 930 (mean age = 94.0 years) Chinese oldest old.

MEASUREMENTS

The TG concentrations were measured at baseline survey in 2009. Cognitive function, ADLs, frailty, and mortality were determined over 5 years of follow-up. Cox proportional hazards models and competing risk models were performed to explore the association, adjusting for potential confounders.

RESULTS

Each 1-mmol/L increase in TGs was associated with a nearly 20% lower risk of cognitive decline, ADL decline, and frailty aggravation during the 5 years of follow-up. Consistently, higher TGs (each 1 mmol/L) was associated with lower 5-year all-cause mortality after fully adjustment (hazard ratio [HR] = 0.79; 95% confidence interval [CI] = 0.69-0.89). Nonelevated TG concentrations (less than 2.26 mmol/L) were associated with higher mortality risk (HR = 1.72; 95% CI = 1.22-2.44), relative to TGs of 2.26 mmol/L or more. We observed similar results regarding TG concentrations and mortality in 1-year lag analysis and when excluding participants with identified chronic disease.

CONCLUSION

In the oldest old, a higher concentration of TGs was associated with a lower risk of cognitive decline, ADL decline, frailty aggravation, and mortality. This paradox suggests the clinical importance of revisiting the concept of "the lower the better" for the oldest old. J Am Geriatr Soc 67:741-748, 2019.

Association of Body Mass Index With Disability in Activities of Daily Living Among Chinese Adults 80 Years of Age or Older

IMPORTANCE

Body mass index (BMI) shows a U-shaped association with impaired physical functioning among adults; the association is reduced or eliminated with aging.

OBJECTIVE

To examine whether BMI is associated with subsequent disability in activities of daily living (ADL) in Chinese adults age 80 years or older.

DESIGN, SETTING, AND PARTICIPANTS

Data were obtained on 16 022 adults age 80 years or older who were able to perform ADL independently at baseline from the Chinese Longitudinal Healthy Longevity Study, a community-based prospective cohort study conducted in 23 provinces of China. The study was initiated in 1998, with follow-up and recruitment of new participants in 2000, 2002, 2005, 2008, 2011, and 2014.

MAIN OUTCOMES AND MEASURES

Disability in ADL was defined as dependence in eating, toileting, bathing, dressing, indoor activities, and/or continence.

RESULTS

Among the 16 022 participants, 45.2% were men and 54.8% were women, with a mean (SD) age of 92.2 (7.2) years and a mean (SD) BMI (calculated as weight in kilograms divided by height in meters squared) of 19.3 (3.8). During 70 606 person-years of follow-up, 8113 participants with disability in ADL were identified. Cox proportional hazards regression models with penalized splines showed that BMI was linearly associated with disability in ADL: each 1-kg/m2 increase in BMI corresponded to a 4.5% decrease in the risk of disability in ADL. In comparison with individuals in the fourth quintile for BMI, the adjusted hazard ratio for disability in ADL was 1.38 (95% CI, 1.29-1.48) in the first quintile, 1.37 (95% CI, 1.28-1.47) in the second quintile, 1.11 (95% CI, 1.04-1.19) in the third quintile, and 0.85 (95% CI, 0.79-0.91) in the fifth quintile (P < .001 for trend). When BMI was categorized by Chinese guidelines, the underweight group (BMI <18.5) showed significantly increased risk of disability in ADL (hazard ratio, 1.34; 95% CI, 1.28-1.41) and the overweight or obese group (BMI ≥24.0) showed significantly decreased risk of disability in ADL (hazard ratio, 0.84; 95% CI, 0.78-0.91) compared with the normal weight group (BMI 18.5 to <24.0) (P < .001 for trend).

CONCLUSIONS AND RELEVANCE

Higher BMI was associated with a lower risk of disability in ADL among Chinese adults age 80 years or older, which suggests that current recommendations for BMI may need to be revisited. More attention should be paid on underweight, rather than overweight or obesity, for the prevention of disability in ADL after age 80 years.

Adiposity-Mortality Relationships in Type 2 Diabetes, Coronary Heart Disease, and Cancer Subgroups in the UK Biobank, and Their Modification by Smoking

OBJECTIVE

The obesity paradox in which overweight/obesity is associated with mortality benefits is believed to be explained by confounding and reverse causality rather than by a genuine clinical benefit of excess body weight. We aimed to gain deeper insights into the paradox through analyzing mortality relationships with several adiposity measures; assessing subgroups with type 2 diabetes, with coronary heart disease (CHD), with cancer, and by smoking status; and adjusting for several confounders.

RESEARCH DESIGN AND METHODS

We studied the general UK Biobank population (N = 502,631) along with three subgroups of people with type 2 diabetes (n = 23,842), CHD (n = 24,268), and cancer (n = 45,790) at baseline. A range of adiposity exposures were considered, including BMI (continuous and categorical), waist circumference, body fat percentage, and waist-to-hip ratio, and the outcome was all-cause mortality. We used Cox regression models adjusted for age, smoking status, deprivation index, education, and disease history.

RESULTS

For BMI, the obesity paradox was observed among people with type 2 diabetes (adjusted hazard ratio for obese vs. normal BMI 0.78 [95% CI 0.65, 0.95]) but not among those with CHD (1.00 [0.86, 1.17]). The obesity paradox was pronounced in current smokers, absent in never smokers, and more pronounced in men than in women. For other adiposity measures, there was less evidence for an obesity paradox, yet smoking status consistently modified the adiposity-mortality relationship.

CONCLUSIONS

The obesity paradox was observed in people with type 2 diabetes and is heavily modified by smoking status. The results of subgroup analyses and statistical adjustments are consistent with reverse causality and confounding.

Associations of Body Mass Index and Waist Circumference with 3-Year All-Cause Mortality Among the Oldest Old: Evidence from a Chinese Community-Based Prospective Cohort Study

OBJECTIVE

Current international and national guidelines for body mass index (BMI) and waist circumference (WC) have been recommended to all adults. However, whether recommendations applied to the oldest old (aged 80+) is poorly known. The study objective was to investigate the relation of BMI and WC with 3-year all-cause mortality among the oldest old.

DESIGN, SETTING, AND PARTICIPANTS

A total of 4361 Chinese oldest old (mean age 91.8) participated in this community-based prospective cohort study.

MEASUREMENTS

BMI and WC were measured at baseline in 2011 and were used as continuous variables and as categorized variables by recommendations or by tertiles. Adjusted, sex-stratified Cox models with penalized splines and Cox models were constructed to explore the association.

RESULTS

Greater BMI and WC were linearly associated with lower mortality risk in both genders. The mortality risk was the lowest in overweight or obese participants (BMI ≥ 24.0) and was lower in participants with abdominal obesity. Compared to the upper tertile, those in the middle and lower tertile of BMI had a higher risk of mortality for men [hazard ratio (HR): 1.23 (1.02-1.48) and 1.53 (1.28-1.82)] and for women [HR: 1.21 (1.03-1.41) and 1.35 (1.15-1.58)]; it was also found in participants in the middle and lower tertile of WC for men [HR: 1.21 (1.01-1.46) and 1.41 (1.18-1.69)] and for women [HR: 1.35 (1.15-1.58) and 1.55 (1.32-1.81)] (all the P values for trend <.001). These findings were robust in further sensitivity analyses or when using propensity score matching, in subgroup analyses, or in octogenarians, nonagenarians, and centenarians.

CONCLUSIONS

In Chinese oldest old, both higher BMI and higher WC predict better survival in both genders. The finding suggests optimal BMI and WC may be sensitive to age, thus, the current recommendations for the oldest old may need to be revisited.

The Evidence for an Obesity Paradox in Type 2 Diabetes Mellitus

Although overweight/obesity is a major risk factor for the development of type 2 diabetes mellitus, there is increasing evidence that overweight or obese patients with type 2 diabetes mellitus experience lower mortality compared with patients of normal weight. This paradoxical finding, known as the "obesity paradox," occurs in other chronic diseases, and in type 2 diabetes mellitus is particularly perplexing given that lifestyle intervention with one goal being weight reduction is an important feature of the management of this condition. We summarize in this review the findings from clinical and epidemiologic studies that have investigated the association between overweight and obesity (usually assessed using body mass index [BMI]) and mortality in type 2 diabetes mellitus and discuss potential causes of the obesity paradox. We conclude that most studies show evidence of an obesity paradox, but important conflicting findings still exist. We also evaluate if potential bias might explain the obesity paradox in diabetes, including, for example, the presence of confounding factors, measurement error due to use of BMI as an index of obesity, and reverse causation.

Body mass index and mortality in patients with and without diabetes mellitus

OBJECTIVE

Investigate the association between body mass index (BMI), length of stay (LOS), and mortality in hospitalized patients with and without diabetes mellitus (DM).

METHODS

Historical prospectively collected data of adult patients hospitalized between 2011 and 2013. Body mass index was calculated according to measurement or self-report on admission and classified as follows: underweight (<18.5), normal weight (18.5-24.9), overweight (25-29.9), obese (30-34.9), and severely obese (≥35). The main outcomes were LOS, in-hospital, and end-of-follow-up mortality.

RESULTS

Cohort included 24 233 patients (53% male; mean age ± SD, 65 ± 18), including 7397 patients with DM (31%). Among patients with normal BMI, LOS was shorter compared with underweight patients, but it was longer compared with overweight and obese patients. Following multivariate adjustment, this difference remained significant only for patients with DM. There was a significant interaction between DM status and BMI group, in the models for in-hospital and end-of-follow-up mortality. Compared with normal BMI, in-hospital mortality risk was increased by 80% and 100% for the underweight with and without DM, respectively. For patients with and without DM, in-hospital mortality risk was 30% to 40% lower among overweight and obese patients, and there was no difference between severely obese and normal weight patients. At the end-of-follow-up, mortality risk was 1.6-fold and 1.7-fold higher among underweight patients with and without DM, respectively. For overweight, obese, and severely obese patients, mortality risk was decreased by 30% to 40% in those with DM and by 20% to 30% in those without DM.

CONCLUSIONS

In hospitalized patients with and without DM, there was an inverse association between BMI and mortality.

Paediatric obesity appears to lower the risk of diabetes if selection bias is ignored

BACKGROUND

Frustrated with the onslaught of articles reporting fascination with results that appear paradoxical but are merely due to selection bias, we studied the apparent effect of obesity on diabetes risk in youth who had a test for diabetes. We hypothesised that obese subjects would have lower rates of diabetes than non-obese subjects due to selection bias, and consequently, obesity would appear to lower the risk of diabetes.

METHODS

Retrospective cohort study of children (4-9 years), pre-teens (10-12 years) and teenagers (13-19 years). Participation was restricted to those who had a test of haemoglobin A1C along with measured height and weight. Body mass index percentile via the Centers for Disease Control and Prevention age and sex standards was calculated and categorised. The main outcome was A1C%, subsequently categorised at the level for diagnosis of diabetes mellitus (≥6.5%).

RESULTS

The sample consisted of 134 (2%) underweight, 1718 (30%) healthy weight, 660 (12%) overweight and 3190 (56%) obese individuals. 16% (n=936) had an A1C≥6.5%. Overall, healthy weight children had 8.2 times the risk of A1C≥6.5% (95% CI 5.3 to 12.7) compared with those in the obese category. The relative risk was 13 in pre-teens (95% CI 8.5 to 20.0) and 3.9 in teenagers (95% CI 3.3 to 4.7).

CONCLUSIONS

Healthy weight was associated with a 4-13 times higher relative risk of diabetes mellitus compared with being obese. While apparently shocking, the study's fatal flaw (selection bias) explains the 'paradoxical' finding. Ignoring selection bias can delay advances in medical science.

Collider Bias Is Only a Partial Explanation for the Obesity Paradox

Supplemental Digital Content is available in the text.

Background:

“Obesity paradox” refers to an association between obesity and reduced mortality (contrary to an expected increased mortality). A common explanation is collider stratification bias: unmeasured confounding induced by selection bias. Here, we test this supposition through a realistic generative model.

Methods:

We quantify the collider stratification bias in a selected population using counterfactual causal analysis. We illustrate the bias for a range of scenarios, describing associations between exposure (obesity), outcome (mortality), mediator (in this example, diabetes) and an unmeasured confounder.

Results:

Collider stratification leads to biased estimation of the causal effect of exposure on outcome. However, the bias is small relative to the causal relationships between the variables.

Conclusions:

Collider bias can be a partial explanation of the obesity paradox, but unlikely to be the main explanation for a reverse direction of an association to a true causal relationship. Alternative explanations of the obesity paradox should be explored. See Video Abstract at http://links.lww.com/EDE/B51.

Impact of obesity on mortality in patients with diabetes: Meta-analysis of 20 studies including 250,016 patients

AIMS/INTRODUCTION

The impact of body mass index on mortality among patients with diabetes remains controversial. Therefore, we carried out a meta-analysis of pertinent studies.

MATERIALS AND METHODS

We searched OVID/MEDLINE, EMBASE and Cochrane databases for all reported studies, which investigated the relationship between body mass index and mortality in patients with diabetes. Summary estimates of hazard ratios (HRs) were obtained with a random effects model. Univariate meta-regressions were carried out.

RESULTS

A total of 20 studies including 250,016 patients with diabetes were identified. The results of the present study showed a significantly reduced risk of all-cause mortality in overweight patients (HR 0.82, 95% CI: 0.74-0.91, P < 0.0001, and I2 = 91.6%) as compared with normal weight patients. The survival benefits of obesity were only observed in the elderly patients (HR 0.69, 95% CI: 0.63-0.75, P < 0.0001, and I2 = 50.4%), but not in the younger patients (HR 1.01, 95% CI: 0.84-1.20, P = 0.96, I2 = 80.1%). Furthermore, the beneficial prognostic impacts on overweight (coefficient = 0.030, P = 0.041) and obesity (coefficient = 0.032, P = 0.010) were attenuated with clinical follow-up duration.

CONCLUSIONS

The present meta-analysis showed a significantly lower risk of all-cause mortality in overweight patients with diabetes compared with normal weight patients. However, the survival benefits of obesity were only observed among the elderly patients.

BMI and All-Cause Mortality in Normoglycemia, Impaired Fasting Glucose, Newly Diagnosed Diabetes, and Prevalent Diabetes: A Cohort Study

OBJECTIVE

This study examined associations between BMI and mortality in individuals with normoglycemia, impaired fasting glucose (IFG), newly diagnosed diabetes, and prevalent diabetes and identified BMI ranges associated with the lowest mortality in each group.

RESEARCH DESIGN AND METHODS

A total of 12,815,006 adults were prospectively monitored until 2013. Diabetes status was defined as follows: normoglycemia (fasting glucose <100 mg/dL), IFG (100-125 mg/dL), newly diagnosed diabetes (≥126 mg/dL), and prevalent diabetes (self-reported). BMI (kg/m²) was measured. Cox proportional hazards model hazard ratios were calculated after adjusting for confounders.

RESULTS

During a mean follow-up period of 10.5 years, 454,546 men and 239,877 women died. U-shaped associations were observed regardless of diabetes status, sex, age, and smoking history. Optimal BMI (kg/m²) for the lowest mortality by group was 23.5-27.9 (normoglycemia), 25-27.9 (IFG), 25-29.4 (newly diagnosed diabetes), and 26.5-29.4 (prevalent diabetes). Higher optimal BMI by worsening diabetes status was more prominent in younger ages, especially in women. The relationship between worsening diabetes status and higher mortality was stronger with lower BMI, especially at younger ages. Given the same BMI, people with prevalent diabetes had higher mortality compared with those with newly diagnosed diabetes, and this was more striking in women than men.

CONCLUSIONS

U-curve relationships existed regardless of diabetes status. Optimal BMI for lowest mortality became gradually higher with worsening diabetes for each sex and each age-group.

Obesity paradox and mortality in adults with and without incident type 2 diabetes: a matched population-level cohort study

OBJECTIVE

Among adults with type 2 diabetes (T2D), several (but not all) studies show that being overweight (body mass index (BMI): 25.0-29.9 kg/m2) or obese I (BMI: 30.0-34.9 kg/m2) near the time of diagnosis, is unexpectedly associated with reduced all-cause mortality compared with normal weight-the obesity paradox. We addressed whether this observation is causal (eg, a true protective effect); due to confounding (including effect modification); or due to selection ('collider') bias.

RESEARCH DESIGN AND METHODS

We performed a matched population-level cohort study using primary care records from Salford, UK (1995-2012) in 10 464 patients with incident T2D paired (1:3) with 31 020 individuals who never developed T2D. We estimated HRs for associations of BMI with all-cause mortality using Cox models, stratified by smoking status.

RESULTS

Median follow-up was 8.7 years. For never smokers, the hazard of all-cause mortality increased from 25 kg/m2, in a linear manner, with increasing BMI in the T2D cohort (HR per 5 kg/m2: 1.23, ptrend<0.001) and in the non-diabetes cohort (HR per 5 kg/m2: 1.34, ptrend<0.001). In contrast, among ever smokers, BMI-mortality relationships were U-shaped in the T2D and non-diabetes cohorts. Evidence of the obesity paradox in ever smokers, with and without T2D, argued against a selection bias, but supported a contribution of effect modification by smoking (pinteraction=0.009). Results were stable to various sensitivity analyses.

CONCLUSIONS

In this cohort, the obesity paradox is mainly explained by smoking as an effect modifier. These findings indicate that the obesity paradox does not challenge standard weight management recommendations among T2D patients.

Body mass index and mortality in patients with type 2 diabetes mellitus: A prospective cohort study of 11,449 participants

AIMS

To investigate the association between body-mass index and mortality in Chinese adults T2DM.

METHODS

11,449 participants of Kailuan Study with T2DM were included in this prospective cohort study. All-cause mortality was calculated using Kaplan-Meier analysis. Cox proportional hazards analysis was used to estimate the association between BMI and mortality.

RESULTS

During a mean follow-up period of 7.25±1.42years, 1254 deaths occurred. The number of deaths of the underweight, normal weight, overweight, and obese group was 23, 389, 557, and 285; the corresponding mortality was 25.0%, 13.4%, 10.3%, and 9.4%, respectively. The obese group had the lowest all-cause mortality rate (log-rank chi-square=48.430, P<0.001). After adjusting for age, sex, fasting blood glucose, smoking status, systolic blood pressure, history of hypertension, stroke, cancer and myocardial infarction, compared with the normal weight group, Multivariate Cox proportional hazard regression analysis showed that HR (95% CI) of all-cause mortality in the underweight, overweight, and obese group was 1.497 (0.962, 2.330), 0.833 (0.728, 0.952), and 0.809 (0.690, 0.949). After stratifying for age tertiles, this trend remained.

CONCLUSIONS

In T2DM patients in north China, the risk for all-cause mortality was lower in the overweight and the obese groups than those in the normal weight and the underweight groups.

Analysis of Body Mass Index and Mortality in Patients With Colorectal Cancer Using Causal Diagrams

IMPORTANCE

Physicians and investigators have sought to determine the relationship between body mass index (BMI [calculated as weight in kilograms divided by height in meters squared]) and colorectal cancer (CRC) outcomes, but methodologic limitations including sampling selection bias, reverse causality, and collider bias have prevented the ability to draw definitive conclusions.

OBJECTIVE

To evaluate the association of BMI at the time of, and following, colorectal cancer (CRC) diagnosis with mortality in a complete population using causal diagrams.

DESIGN, SETTING, AND PARTICIPANTS

This retrospective observational study with prospectively collected data included a cohort of 3408 men and women, ages 18 to 80 years, from the Kaiser Permanente Northern California population, who were diagnosed with stage I to III CRC between 2006 and 2011 and who also had surgery.

EXPOSURES

Body mass index at diagnosis and 15 months following diagnosis.

MAIN OUTCOMES AND MEASURES

Hazard ratios (HRs) for all-cause mortality and CRC-specific mortality compared with normal-weight patients, adjusted for sociodemographics, disease severity, treatment, and prediagnosis BMI.

RESULTS

This study investigated a cohort of 3408 men and women ages 18 to 80 years diagnosed with stage I to III CRC between 2006 and 2011 who also had surgery. At-diagnosis BMI was associated with all-cause mortality in a nonlinear fashion, with patients who were underweight (BMI <18.5; HR, 2.65; 95% CI, 1.63-4.31) and patients who were class II or III obese (BMI ≥35; HR, 1.33; 95% CI, 0.89-1.98) exhibiting elevated mortality risks, compared with patients who were low-normal weight (BMI 18.5 to <23). In contrast, patients who were high-normal weight (BMI 23 to <25; HR, 0.77; 95% CI, 0.56-1.06), low-overweight (BMI 25 to <28; HR, 0.75; 95% CI, 0.55-1.04), and high-overweight (BMI 28 to <30; HR, 0.52; 95% CI, 0.35-0.77) had lower mortality risks, and patients who were class I obese (BMI 30 to <35) showed no difference in risk. Spline analysis confirmed a U-shaped relationship in participants with lowest mortality at a BMI of 28. Associations with CRC-specific mortality were similar. Associations of postdiagnosis BMI and mortality were also similar, but patients who were class I obese had significantly lower all-cause and cancer-specific mortality risks.

CONCLUSIONS AND RELEVANCE

In this study, body mass index at the time of diagnosis and following diagnosis of CRC was associated with mortality risk. Though evidence shows that exercise in patients with cancer should be encouraged, findings suggest that recommendations for weight loss in the immediate postdiagnosis period among patients with CRC who are overweight may be unwarranted.

Obesity and Energy Balance in GI Cancer

The prevalence of overweight (body mass index [BMI], 25 to 29.9 kg/m2) and obesity (BMI ≥ 30 kg/m2) have increased dramatically in the United States. Because increasing BMI is associated with the development of multiple different cancer types, including most GI cancers, providers will frequently encounter patients with GI cancer who are overweight or obese. Mounting evidence associates overweight and/or obesity with worsened prognosis in multiple GI cancers, including esophageal, gastric, hepatocellular, pancreatic, and colorectal. However, these data are observational and may be subject to bias and/or confounding. Furthermore, in some cancer types, the associations between BMI and outcomes is not linear, where overweight and class I obese patients may have an improvement in outcome. This report provides a brief highlight of existing studies that have linked overweight and/or obesity to prognosis in GI cancer; provides recommendations on best management practices; and discusses limitations, controversies, and future directions in this rapidly evolving area. There are multiple areas of promise that warrant continued investigation: What are the comparative contributions of energy balance, including weight, dietary patterns, and physical activity on cancer prognosis? What are the specific physiologic pathways that mediate the relationship between energy balance and prognosis? What is the relationship between low muscle mass (sarcopenia) or sarcopenic obesity and cancer prognosis? Are there subsets of patients for whom purposefully altering energy balance would be deleterious to prognosis? This area is rich with opportunities to understand how states of energy (im)balance can be favorably altered to promote healthy survivorship.

Impact of alcohol consumption and body mass index on mortality from nonneoplastic liver diseases, upper aerodigestive tract cancers, and alcohol use disorders in Korean older middle-aged men: Prospective cohort study

Alcohol use is a leading risk factor for the global disease burden including liver diseases. However, the combined effect of alcohol use and body mass index (BMI) on alcohol-related diseases has seldom been examined. We examined whether alcohol consumption and BMI could act together to increase mortality from nonneoplastic liver diseases, upper aero-digestive tract (UADT) cancers, and alcohol use disorders (AUD) in middle-aged Korean men.107,735 men (mean age, 58.8 years) participated in a postal survey in 2004 and were followed until 2010, by linkage to national death records. Hazard ratios (HRs) of cause-specific death were calculated after adjustment for confounders.Each 5-drink (approximately 45 g alcohol) higher weekly alcohol consumption was associated with increased mortality, by approximately 70% for nonneoplastic liver disease mortality (HR = 1.70, P < 0.001), approximately 60% for UADT cancer mortality (HR = 1.64, P < 0.001), and approximately 70% for AUD mortality (HR = 1.71, P < 0.001). Generally, BMI was inversely associated with these alcohol-related diseases (HR per each 5 kg/m higher BMI = 0.18-0.46, P < 0.001 for each cause), while, in participants with BMI ≥25 kg/m, each 5 kg/m higher BMI was also associated with an elevated mortality from nonneoplastic liver diseases of approximately 150% (HR = 2.52, P = 0.001). Men with BMI < 21 kg/m and weekly alcohol consumption ≥14 drinks showed markedly higher mortality from nonneoplastic liver diseases (HR = 5.7), alcoholic liver diseases (HR = 9.3), UADT cancers (HR = 10.5), and esophageal cancer (HR = 15.5), compared to men drinking less than 1 drink/wk with BMI ≥25 kg/m. The combined effect of low BMI and high weekly alcohol consumption was 2.25- to 3.29-fold greater than the additive effect of each factor for these alcohol-related diseases (P < 0.05 for each cause).Alcohol consumption and low BMI were related to deaths from nonneoplastic liver diseases, UADT cancers, and AUD, with evidence of a supra-additive combined effect of both factors. High BMI was also related to deaths from nonneoplastic liver diseases. Men with a low BMI (<23 kg/m) are suggested to be prone to the harmful effects of alcohol.

Obesity paradox in patients with community-acquired pneumonia: Is inflammation the missing link?

OBJECTIVE

Positive associations between body mass index (BMI) and clinical outcomes have been found and are called "the obesity survival paradox." However, whether obesity has protective effects or if this paradox is because of confounding remains unclear. Herein, we analyzed the effects of weight on long-term mortality in a large cohort of patients with community-acquired pneumonia (CAP) and investigated whether the differential effects of obesity on inflammation pathways accounted for mortality differences.

METHODS

For this secondary analysis, we followed prospectively for 6 y 763 CAP patients who were previously included in a multicenter trial (the ProHOSP Trial). To assess associations of BMI with mortality and with several inflammatory biomarker levels, we calculated three regression models adjusted for severity: the pneumonia severity index (PSI); fully adjusted for PSI, age, sex, metabolic factors, cardiovascular diseases, and other comorbidities; and fully adjusted including biomarker levels.

RESULTS

Within the 763 patients studied, all-cause 6-y mortality was significantly lower in obese patients (BMI >30 kg/m²) compared with normal-weight patients (BMI 18.5-25 kg/m²), with a severity-adjusted hazard ratio of 0.641 (95% confidence interval 0.462-0.889) and robust results in fully adjusted and fully adjusted plus biomarker models. No associations of increased BMI and C-reactive protein, procalcitonin, or white blood cell count were found, but BMI > 30 kg/m² was associated with higher proadrenomedullin levels.

CONCLUSIONS

Over a 6-y long-term follow-up, we found obesity to be associated with lower all-cause mortality in CAP patients, confirming the obesity paradox in this population. However, differences in inflammatory pathways did not explain these findings.