Causal associations of body mass index and waist-to-hip ratio with cardiometabolic traits among Chinese children: A Mendelian randomization study

Changes in general and abdominal obesity in children at 4, 6 and 9 years of age and their association with other cardiometabolic risk factors

Temporary changes in childhood obesity and their association with cardiometabolic risk factors have been receiving increased attention. The objective of this study was to evaluate changes in general (GO) and abdominal (AO) obesity in children from 4 to 9 years of age and their associations with cardiometabolic risk factors at 9 years of age. This study includes 1344 children from the Longitudinal Childhood Obesity Study (ELOIN). Physical examinations performed at 4, 6 and 9 years of age and a blood sample was only taken at 9 years of age. Changes in obesity from 4 to 9 years of age were estimated using Body Mass Index and waist circumference. Participants were classified into four groups according to GO and AO: (1) stable without obesity (no obesity at all three measurements); (2) remitting obesity at 9 years (obesity at 4 and/or 6 years but not at 9 years); (3) incident or recurrent obesity at 9 years (obesity only at 9 years, at 4 and 9 years or at 6 and 9 years); and (4) stable or persistent with obesity (obesity at 4, 6 and 9 years). Dyslipidemia and dysglycemia were defined by the presence of at least one altered parameter of the lipid or glycemic profile. Odds ratios (OR) were estimated using logistic regression. Compared with children without GO at all ages, those with persistent GO had an OR of 3.66 (95% CI: 2.06-6.51) for dyslipidemia, 10.61 (95% CI: 5.69-19.79) for dysglycemia and 8.35 (95% CI: 4.55-15.30) for high blood pressure. The associations were fairly similar in the case of AO, with ORs of 3.52 (95% CI: 1.96-6.34), 17.15 (95% CI: 9.09-32.34) and 8.22 (95% CI: 4.46-15.15), respectively, when comparing persistent versus stable without AO. Children with incident obesity at 9 years presented a moderate cardiometabolic risk that was nevertheless higher compared to those stable without obesity, whereas those with remitting obesity did not show any significant associations.

CONCLUSION

Incident, and especially, persistent obesity, is associated with an increased cardiometabolic risk. The very early prevention of obesity, with a focus on nutrition, physical activity and sedentary behaviour, as well as tracking growth from birth to age 5, should be a priority to prevent the burden of cardiometabolic disease with consequences for adulthood.

WHAT IS KNOWN

• General and abdominal obesity has been shown to be associated with other cardiometabolic risk factors such as dyslipidemia, insulin resistance and hypertension. • Temporary changes in obesity and their associations with cardiometabolic risk factors have not been sufficiently explored in childhood.

WHAT IS NEW

• Children with incident, and especially persistent, general and/or abdominal obesity, had an increased risk of dyslipidemia, dysglycemia and high blood pressure. •Remitting obesity was not associated with an increased cardiometabolic risk.

Body fatness associations with cancer: evidence from recent epidemiological studies and future directions

This narrative review highlights current evidence linking greater body fatness to risk of various cancers, with focus on evidence from recent large cohort studies and pooled analyses of cohort studies as well as Mendelian randomization studies (which utilized genetic variants associated with body mass index to debrief the causal effect of higher body fatness on cancer risk). This review also provides insights into the biological mechanisms underpinning the associations. Data from both observational and Mendelian randomization studies support the associations of higher body mass index with increased risk of many cancers with the strongest evidence for digestive system cancers, including esophageal, stomach, colorectal, liver, gallbladder, and pancreatic cancer, as well as kidney, endometrial, and ovarian (weak association) cancer. Evidence from observational studies suggests that greater body fatness has contrasting effects on breast cancer risk depending on menopausal status and on prostate cancer risk depending on disease stage. Experimental and Mendelian randomization studies indicate that adiponectin, insulin, and sex hormone pathways play an important role in mediating the link between body fatness and cancer risk. The possible role of specific factors and pathways, such as other adipocytokines and hormones and the gut microbiome in mediating the associations between greater body fatness and cancer risk is yet uncertain and needs investigation in future studies. With rising prevalence of overweight and obesity worldwide, the proportion of cancer caused by excess body fatness is expected to increase. There is thus an urgent need to identify efficient ways at the individual and societal level to improve diet and physical activity patterns to reduce the burden of obesity and accompanying comorbidities, including cancer.

Distinct causal effects of body fat distribution on cardiometabolic traits among children: Findings from the BCAMS study

BACKGROUND AND AIMS

Observational studies reveal that different body fat measures are associated with cardiometabolic disease with different effects. However, causality is not reflected by such observations. To explore and compare the causal relationships of general obesity (measured by body mass index (BMI)), adipose obesity (measured by fat mass percentage (FMP)) and central obesity (measured by waist-to-height ratio (WHtR)) with cardiometabolic traits among children.

METHODS AND RESULTS

We conducted one sample Mendelian randomization (MR) analysis in 3266 children from Beijing Children and Adolescents Metabolic Syndrome Study. Genetic instruments based on 28 SNPs were performed to explore and compare the causal associations of genetically BMI, FMP and WHtR with cardiometabolic traits. The genetic instruments were robustly correlated with observed BMI, FMP and WHtR. Each genetically 1-SD increment in BMI, FMP and WHtR were causally associated with increment in systolic blood pressure (SBP), diastolic blood pressure (DBP), log-transformed fasting plasma glucose (FPG), log-transformed HOMA-β, and decrease in log-transformed high-density lipoprotein cholesterol (HDL), respectively (all P < 0.05 after Bonferroni correction). The receiver operating characteristic curve indicated that BMI and FMP showed stronger effects on SBP, DBP, HOMA-β and HDL than WHtR (all P < 0.05). We also observed causal associations of BMI and FMP with log-transformed fasting insulin and HOMA-IR.

CONCLUSIONS

The MR analysis based on population-based cohort indicated a causal relationship of adiposity and body fat distribution with cardiometabolic traits. When compared with central obesity, general obesity and adipose obesity might own stronger effects on blood pressure and blood lipids among children.

Tracking and risk of abdominal and general obesity in children between 4 and 9 years of age. The Longitudinal Childhood Obesity Study (ELOIN)

BACKGROUND

Studies have shown that overweight and obesity conditions tend to be stable from childhood and adolescence to adulthood. Unfortunately, little is known about the evolution of abdominal obesity during childhood. The aim of this study was to evaluate the temporal variations and risk of general and abdominal obesity between 4, 6, and 9 years of age.

METHODS

Measurements of children in the ELOIN study taken at the three follow-ups of 4, 6, and 9 years of age were included (N = 1,902). Body mass index and waist circumference were recorded via physical examination. General obesity was determined according to the criteria of the World Health Organization (WHO) and abdominal obesity according to the cut-off points proposed by the International Diabetes Federation (IDF). Prevalence ratios (PRs) were estimated by sex and family affluence using generalized estimating equation models and relative risks (RRs) of obesity were obtained via Poisson regression.

RESULTS

The prevalence of general obesity was 5.1%, 9.1%, and 15.6% at 4, 6, and 9 years, respectively, yielding a PR of 3.05 (95%CI: 2.55-3.60) (9 years old relative to 4 years). The prevalence of abdominal obesity was 6.8%, 8.4%, 14.5% at 4, 6, and 9 years, respectively, and the PR was 2.14 (95%CI: 1.82-2.51) (9 years old relative to 4 years). An inverse correlation was observed between both general and abdominal obesity and socioeconomic status. Among participants with general or abdominal obesity at 4 years of age, 77.3% and 63.6% remained in their obesity classification at 9 years, respectively, and 3.4% and 3.5% presented general or abdominal obesity also at 6 and 9 years of age, respectively. The RRs of general and abdominal obesity at 9 years were 4.61 (95%CI: 2.76-7.72) and 4.14 (95%CI: 2.65-6.48) for children classified with obesity at 4 years of age, increased to 9.36 (95%CI: 7.72-11.35) and 9.56 (95%CI: 7.79-11.74) for children who had obesity at 6 years, and up to 10.27 (95%CI: 8.52-12.37) and 9.88 (95%CI: 8.07-12.11) for children with obesity at both 4 and 6 years, respectively.

CONCLUSIONS

General and abdominal obesity begin at an early age and increase over time, showing an inverse correlation with socioeconomic status. In addition, general and abdominal obesity at 9 years are strongly associated with being classified with obesity at 4 and 6 years, so preventive interventions should be established at very early ages.

Association between waist-hip ratio and subclinical myocardial injury in the general population: Insights from the NHANES

BACKGROUND

Although studies have shown that higher waist-hip ratio (WHR) is closely related to higher risk of metabolism-related diseases, the relationship between WHR and subclinical myocardial injury (SC-MI) is unknown. This study was to evaluate the effect of WHR on SC-MI in the general population free from cardiovascular disease.

METHODS

The cross-sectional study included 6253 participants without cardiovascular disease (CVD) from the third National Health and Nutrition Examination Survey (NHANES III) for further analysis. Restricted cubic spline, multivariable logistic regression models and subgroup analyses were performed to assess the association between WHR and SC-MI.

RESULTS

The multivariate logistic regression showed that after adjusting for potential confounding factors, participants in the higher quartiles had higher risk of developing SC-MI than those in the first quartile of WHR [Q3, OR (95% CI): 1.523 (1.159, 2.000), P = 0.002; Q4, OR (95% CI): 1.719 (1.279, 2.311), P < 0.001], and this relationship was robust among the participants aged ≥ 50 years, with hypertension and without diabetes. Every 0.1 unit increase in WHR, as a continuous variable, increased the risk of SC-MI by more than 20% [OR (95% CI): 1.233 (1.092, 1.392), P = 0.001]. And restricted cubic spline analysis showed that there was a linear positive correlation between WHR and the risk of SC-MI.

CONCLUSIONS

WHR may be an independent risk factor for SC-MI in the general population free from CVD.