Beyond BMI: How to Capture Influences from Body Composition in Health Surveys

Changes in body mass index and its association with socio-demographic characteristics between 2010 and 2016 in Singapore

Background

Epidemiological studies have observed an increase in the prevalence of obesity in both western and Asian countries. This study aims to compare the distribution of body mass index (BMI) in the general population of Singapore between 2010 and 2016, and to explore the socio-demographic risk factors associated with it.

Methods

Data for this study were extracted from two national-wise studies in 2010 and 2016, two population-based, cross-sectional epidemiological studies. BMI cut-off scores were used as an indicator to assess obesity in this study, and the data included in the analysis was self-reported by the respondents.

Results

Overall, the study observed decreasing prevalence in underweight and normal weight categories; and an increasing prevalence in overweight and obesity categories in the Singapore adult population between 2010 and 2016. Age, gender, ethnicity, marital status, and educational level were found to be significantly associated with BMI categories.

Conclusion

The observed increase in the population's BMI between 2010 and 2016 may lead to an increase in the incidence of chronic diseases in Singapore. Our study findings add to the existing local literature and provides data for evidence-based policymaking on health-related interventions and program planning.

Stratified Probabilistic Bias Analysis for Body Mass Index-related Exposure Misclassification in Postmenopausal Women

BACKGROUND

There is widespread concern about the use of body mass index (BMI) to define obesity status in postmenopausal women because it may not accurately represent an individual's true obesity status. The objective of the present study is to examine and adjust for exposure misclassification bias from using an indirect measure of obesity (BMI) compared with a direct measure of obesity (percent body fat).

METHODS

We used data from postmenopausal non-Hispanic black and non-Hispanic white women in the Women's Health Initiative (n=126,459). Within the Women's Health Initiative, a sample of 11,018 women were invited to participate in a sub-study involving dual-energy x-ray absorptiometry scans. We examined indices of validity comparing BMI-defined obesity (≥30 kg/m), with obesity defined by percent body fat. We then used probabilistic bias analysis models stratified by age and race to explore the effect of exposure misclassification on the obesity-mortality relationship.

RESULTS

Validation analyses highlight that using a BMI cutpoint of 30 kg/m to define obesity in postmenopausal women is associated with poor validity. There were notable differences in sensitivity by age and race. Results from the stratified bias analysis demonstrated that failing to adjust for exposure misclassification bias results in attenuated estimates of the obesity-mortality relationship. For example, in non-Hispanic white women 50-59 years of age, the conventional risk difference was 0.017 (95% confidence interval = 0.01, 0.023) and the bias-adjusted risk difference was 0.035 (95% simulation interval = 0.028, 0.043).

CONCLUSIONS

These results demonstrate the importance of using quantitative bias analysis techniques to account for nondifferential exposure misclassification of BMI-defined obesity. See video abstract at, http://links.lww.com/EDE/B385.

Overweight and Cognitive Performance: High Body Mass Index Is Associated with Impairment in Reactive Control during Task Switching

The prevalence of weight problems is increasing worldwide. There is growing evidence that high body mass index (BMI) is associated with frontal lobe dysfunction and deficits in cognitive control. The present study aims to clarify the association between weight status and the degree of impairment in cognitive flexibility, i.e., the ability to efficiently switch from one task to another, by disentangling the preparatory and residual domains of task switching. Twenty-six normal weight (BMI < 25, five males) and twenty-six overweight (BMI ≥ 25, seven males) university students performed a task-switching paradigm that provides a relatively well-established diagnostic measure of proactive vs. reactive control with regard to cognitive flexibility. Compared to individuals with a BMI lower than 25, overweight (i.e., ≥25) was associated with increased switching costs in the reactive switching condition (i.e., when preparation time is short), representing reduced cognitive flexibility in the preparatory domain. In addition, the overweight group reported significantly more depression and binge eating symptoms, although still indicating minimal depression. No between-group differences were found with regard to self-reported autism spectrum symptoms, impulsiveness, state- and trait anxiety, and cognitive reactivity to depression. The present findings are consistent with and extend previous literature showing that elevated BMI in young, otherwise healthy individuals is associated with significantly more switching costs due to inefficiency in the retrieval, implementation, and maintenance of task sets, indicating less efficient cognitive control functioning.