Trends in group inequalities and interindividual inequalities in BMI in the United States, 1993-2012

Family cash transfers in childhood and birthing persons and birth outcomes later in life

Much literature in the US documents an intergenerational transmission of birthing person and perinatal morbidity in socioeconomically disadvantaged groups. A separate line of work indicates that family cash transfers may improve life chances of low-income families well into adulthood. By exploiting a quasi-random natural experiment of a large family cash transfer among a southeastern American Indian (AI) tribe in rural North Carolina, we examine whether a "perturbation" in socioeconomic status during childhood improves birthing person/perinatal outcomes when they become parents themselves. We acquired birth records on 6805 AI and non-AI infants born from 1995 to 2018. Regression methods to examine effect modification tested whether the birthing person's American Indian (AI) status and exposure to the family cash transfer during their childhood years corresponds with improvements in birthing person and perinatal outcomes. Findings show an increase in age at childbearing (coef: 0.15 years, 95% confidence interval [CI]: 0.05, 0.25) and a decrease in pre-pregnancy body mass index (BMI; coef: -0.42, 95% CI: -0.76, -0.09) with increased duration of cash transfer exposure during childhood. The odds of large-for-gestational age at delivery, as well as mean infant birthweight, is also reduced among AI births whose birthing person had relatively longer duration of exposure to the cash transfer. We, however, observe no relation with other birthing person/perinatal outcomes (e.g., tobacco use during pregnancy, preterm birth). In this rural AI population, cash transfers in one generation correspond with improved birthing person and infant health in the next generation.

Secular trends of asthma mortality in China and the United States from 1990 to 2019

BACKGROUND

Asthma imposes a large healthcare burden in China and the United States (US). However, the trends of asthma mortality and the relative risk factors have not been comparatively analyzed between the countries. The aim of this study was to compare the mortality and risk factors between China and the US.

METHODS

The deaths, and mortality rates of asthma in China and the US during 1990-2019 were obtained from the Global Burden of Disease Study 2019. The age-period-cohort model was used to estimate these mortality rates based on a log-linear scale with additive age, period, and cohort effects. The population attributable fractions of risk factors for asthma were estimated.

RESULTS

In 1990-2019, the asthma mortality rate was higher in China than in the US. The crude and age-standardized asthma mortality rates trended downward in both China and the US from 1990 to 2019. The decline in mortality was more obvious in China. Mortality gap between the two countries was narrowing. A sex difference in asthma mortality was observed with higher mortality in males in China and females in the US. The age effects showed that mortality increased with age in adults older than 20 years, particularly in the elderly. Downward trends were generally observed in the period and cohort rate ratios in both countries, with China experiencing a more obvious decrease. Smoking and high body mass index (BMI) were the leading risk factors for asthma mortality in China and the US, respectively. Mortality attributable to occupational asthmagens and smoking decreased the most in China and the US, respectively.

CONCLUSIONS

In 1990-2019, the asthma mortality rate was higher in China than in the US; however, the mortality gap has narrowed. Mortality increased with age in adults. The improvements in asthma death risk with period and birth cohort were more obvious in China than in the US. Smoking, high BMI, and aging are major health problems associated with asthma control. The role of occupational asthmagens in asthma mortality underscores the importance of management and prevention of occupational asthma.

Trends in the ability of socioeconomic position to predict individual body mass index: an analysis of repeated cross-sectional data, 1991-2019

BACKGROUND

The widening of group-level socioeconomic differences in body mass index (BMI) has received considerable research attention. However, the predictive power of socioeconomic position (SEP) indicators at the individual level remains uncertain, as does the potential temporal variation in their predictive value. Examining this is important given the increasing incorporation of SEP indicators into predictive algorithms and calls to reduce social inequality to tackle the obesity epidemic. We thus investigated SEP differences in BMI over three decades of the obesity epidemic in England, comparing population-wide (SEP group differences in mean BMI) and individual-level (out-of-sample prediction of individuals' BMI) approaches to understanding social inequalities.

METHODS

We used repeated cross-sectional data from the Health Survey for England, 1991-2019. BMI (kg/m2) was measured objectively, and SEP was measured via educational attainment, occupational class, and neighbourhood index of deprivation. We ran random forest models for each survey year and measure of SEP adjusting for age and sex.

RESULTS

The mean and variance of BMI increased within each SEP group over the study period. Mean differences in BMI by SEP group also increased: differences between lowest and highest education groups were 1.0 kg/m2 (0.4, 1.6) in 1991 and 1.3 kg/m2 (0.7, 1.8) in 2019. At the individual level, the predictive capacity of SEP was low, though increased in later years: including education in models improved predictive accuracy (mean absolute error) by 0.14% (- 0.9, 1.08) in 1991 and 1.05% (0.18, 1.82) in 2019. Similar patterns were obtained for occupational class and neighbourhood deprivation and when analysing obesity as an outcome.

CONCLUSIONS

SEP has become increasingly important at the population (group difference) and individual (prediction) levels. However, predictive ability remains low, suggesting limited utility of including SEP in prediction algorithms. Assuming links are causal, abolishing SEP differences in BMI could have a large effect on population health but would neither reverse the obesity epidemic nor reduce much of the variation in BMI.

An electronic medical records study of population obesity prevalence in El Paso, Texas

BACKGROUND

In this study, we determine the feasibility of using electronic medical record (EMR) data to determine obesity prevalence at the census tract level in El Paso County, Texas, located on the U.S.-Mexico border.

METHODS

2012-2018 Body Mass Index (BMI kg/m²) data from a large university clinic system in was geocoded and aggregated to a census tract level. After cleaning and removing duplicate EMR and unusable data, 143,524 patient records were successful geocoded. Maps were created to assess representativeness of EMR data across census tracts, within El Paso County. Additionally, maps were created to display the distribution of obesity across the same geography.

RESULTS

EMR data represented all but one El Paso census tract. Representation ranged from 0.7% to 34.9%. Greatest representation were among census tracts in and around clinics. The mean EMR data BMI (kg/m²) was 30.1, this is approximately 6% less than the 36.0% estimated for El Paso County using the Behavioral Risk Factor Surveillance Study (BRFSS) estimate. At the census tract level, obesity prevalence ranged from 26.6 to 57.6%. The highest obesity prevalence were in areas that tended to be less affluent, with a higher concentration of immigrants, poverty and Latino ethnic concentration.

CONCLUSIONS

EMR data use for obesity surveillance is feasible in El Paso County, Texas, a U.S.-Mexico border community. Findings indicate substantial obesity prevalence variation between census tracts within El Paso County that may be associated with population distributions related to socioeconomics.

Social position and anthropometric status among adults in the ELSA-Brasil study: a latent class analysis

The objective of the present study was to evaluate the association between social position and anthropometric status in women and men Brazilian adult. This was a cross-sectional study that used baseline data collected from 2008 to 2010 for the Brazilian Longitudinal Study of Adult Health (ELSA-Brasil, in Portuguese), in the six major Brazilian state capital cities. A total of 15,105 active and retired civil servants aged from 35 to 74 years. Two latent variables were defined by latent class analysis, social position and anthropometric status. Both constructs and the analyses were separately evaluated by sex. Associations were assessed using multivariate logistic regression analysis with adjustment for age, self-reported skin color/race, and marital status. Around 44% of the women and 26% of the men were classified as overweight or obese. Social position tended to be lower in women (43.2%) and higher among men (40.4%). Heavier women were more likely to be black and brown-skinned, whereas slimmer women were more likely to be white. After adjustment, women's weight increased as social position decreased (OR = 1.52; 95%CI: 1.36-1.70), whereas in men weight decreased as social position decreased (OR = 0.87; 95%CI: 0.76-0.99). Social position affected the anthropometric status of women and men differently, with body patterns also being affected by ethnicity/skin color, showing the potentiality of taking the intersectional perspective when investigating the possible social determinants of the phenomenon.

Age-Group Differences in Body Mass Index, Weight, and Height in Adults With Down Syndrome and Adults With Intellectual Disability From the United States

The authors examined if body mass index (BMI), weight, and height across age groups differ between adults with Down syndrome (DS) and adults with intellectual disability but without DS. They conducted secondary analyses of cross-sectional data from 45,803 individuals from the United States from 2009 to 2014 of the National Core Indicators Adult Consumer Survey across five age groups: 18-29, 30-39, 40-49, 50-59, and 60+ years. For both men and women with DS, BMI and weight increased between the 18- to 29- and the 30- to 39-year age groups and decreased thereafter. For both men and women with intellectual disability, BMI and weight increased between the 18- to 29- and the 30- to 39-year age groups, stayed about the same until the 50- to 59-year age group, and decreased thereafter. Height demonstrated a small but significant decrease with older age in all groups. These cross-sectional comparisons indicate that BMI and weight may start decreasing at a younger age in adults with DS than in adults with intellectual disability.

Can shorter mothers have taller children? Nutritional mobility, health equity and the intergenerational transmission of relative height

This study develops the concept of nutritional mobility, defined here as the probability that a mother ranked low in her cohort's height distribution will have a child who attains a higher rank order. We demonstrate that rank-order regression provides a robust metric of health equity, revealing differences in opportunities for each child to reach their own growth potential. We estimate four indicators of nutritional mobility and test for associations between nutritional mobility and various local economic and environmental factors. Nutritional mobility has improved over time, and the nutrition environment contributes about 2.86 times as much as a mother's height to her child's expected rank in height-for-age. Populations with the least mobility are in Latin America, and the most mobility is in more urbanized areas of Africa and Asia. Rank-order mobility is an important aspect of health equity, offering valuable insight into the role of socioecological factors in nutrition improvement across generations.

The Relative Contributions of Socioeconomic and Genetic Factors to Variations in Body Mass Index Among Young Adults

In light of recent findings on the small proportion of variance in body mass index (BMI) explained by shared environment, and growing interests in the role of genetic susceptibility, we assessed the relative contribution of socioeconomic status (SES) and genome-wide polygenic score for BMI to explaining variation in BMI. Our final analytic sample included 4,918 White and 1,546 Black individuals from the US National Longitudinal Study of Adolescent to Adult Health Wave IV (2007-2008) who had complete measures on BMI, demographics, SES, genetic data, and health behaviors. We used ordinary least-squares regression to assess variation in log(BMI) as a function of the aforementioned predictors, independently and mutually adjusted. All analyses were stratified by race/ethnicity in the main analysis, and further by sex. The age-adjusted variation in log(BMI) was 0.055 among Whites and 0.066 among Blacks. The contribution of SES and polygenic score ranged from less than1% to 6% and from 2% to 8%, respectively, and majority of the variation (87%-96%) in log(BMI) remained unexplained. Differential distribution of socioeconomic resources, stressors, and buffers may interact to produce systematically larger variation in vulnerable populations. More understanding of the contribution of biological, genetic, and environmental factors, as well as stochastic elements, in diverse phenotypic variance is needed in population health sciences.

The role of body mass index at diagnosis of colorectal cancer on Black-White disparities in survival: a density regression mediation approach

The study of racial/ethnic inequalities in health is important to reduce the uneven burden of disease. In the case of colorectal cancer (CRC), disparities in survival among non-Hispanic Whites and Blacks are well documented, and mechanisms leading to these disparities need to be studied formally. It has also been established that body mass index (BMI) is a risk factor for developing CRC, and recent literature shows BMI at diagnosis of CRC is associated with survival. Since BMI varies by racial/ethnic group, a question that arises is whether differences in BMI are partially responsible for observed racial/ethnic disparities in survival for CRC patients. This article presents new methodology to quantify the impact of the hypothetical intervention that matches the BMI distribution in the Black population to a potentially complex distributional form observed in the White population on racial/ethnic disparities in survival. Our density mediation approach can be utilized to estimate natural direct and indirect effects in the general causal mediation setting under stronger assumptions. We perform a simulation study that shows our proposed Bayesian density regression approach performs as well as or better than current methodology allowing for a shift in the mean of the distribution only, and that standard practice of categorizing BMI leads to large biases when BMI is a mediator variable. When applied to motivating data from the Cancer Care Outcomes Research and Surveillance (CanCORS) Consortium, our approach suggests the proposed intervention is potentially beneficial for elderly and low-income Black patients, yet harmful for young or high-income Black populations.

Detecting and correcting for bias in Mendelian randomization analyses using Gene-by-Environment interactions

Background

Mendelian randomization (MR) has developed into an established method for strengthening causal inference and estimating causal effects, largely due to the proliferation of genome-wide association studies. However, genetic instruments remain controversial, as horizontal pleiotropic effects can introduce bias into causal estimates. Recent work has highlighted the potential of gene–environment interactions in detecting and correcting for pleiotropic bias in MR analyses.

Methods

We introduce MR using Gene-by-Environment interactions (MRGxE) as a framework capable of identifying and correcting for pleiotropic bias. If an instrument–covariate interaction induces variation in the association between a genetic instrument and exposure, it is possible to identify and correct for pleiotropic effects. The interpretation of MRGxE is similar to conventional summary MR approaches, with a particular advantage of MRGxE being the ability to assess the validity of an individual instrument.

Results

We investigate the effect of adiposity, measured using body mass index (BMI), upon systolic blood pressure (SBP) using data from the UK Biobank and a single weighted allelic score informed by data from the GIANT consortium. We find MRGxE produces findings in agreement with two-sample summary MR approaches. Further, we perform simulations highlighting the utility of the approach even when the MRGxE assumptions are violated.

Conclusions

By utilizing instrument–covariate interactions in MR analyses implemented within a linear-regression framework, it is possible to identify and correct for horizontal pleiotropic bias, provided the average magnitude of pleiotropy is constant across interaction-covariate subgroups.

Rising prevalence of BMI ≥40 kg/m2 : A high-demand epidemic needing better documentation

Whilst previously rare, some surveys indicate substantial increases in the population with body mass index (BMI) ≥40 kg/m2 since the 1980s. Clinicians report emerging care challenges for this population, often with high resource demands. Accurate prevalence data, gathered using reliable methods, are needed to inform health care practice, planning, and research. We searched digitally for English language sources with measured prevalence data on adult BMI ≥40 collected since 2010. The search strategy included sources identified from recent work by NCD-RisC (2017), grey sources, a literature search to find current sources, and digital snowball searching. Eighteen countries, across five continents, reported BMI ≥40 prevalence data in surveys since 2010: 12% of eligible national surveys examined. Prevalence of BMI ≥40 ranged from 1.3% (Spain) to 7.7% (USA) for all adults, 0.7% (Serbia) to 5.6% (USA) for men, and 1.8% (Poland) to 9.7% (USA) for women. Limited trend data covering recent decades support significant growth of BMI ≥40 population. Methodological limitations include small samples and data collection methods likely to exclude people with very high BMIs. BMI ≥40 data are not routinely reported in international surveys. Lack of data impairs surveillance of population trends, understanding of causation, and societal provision for individuals living with higher weights.

Heterogeneity in adult anthropometry by socioeconomic factors: Indian National Family Health Survey 2006 and 2016

BACKGROUND/OBJECTIVES

Recent evidence suggests nonconstant nature of dispersion in adult women's body mass index (BMI) across sociodemographic groups. The overall variances in BMI and height are also shown to have substantially changed over time. We modeled complex variation in adults' anthropometry-BMI and height-by wealth and education, and assessed their differences over time in India.

SUBJECTS/METHODS

Data from a total of 768,130 women and 180,691 men from the Indian National Family Health Survey (NFHS) 2006 and 2016 were used for the analysis. The average association between wealth and education with anthropometry was assessed from linear regression models assuming constant variance. Individual heterogeneity was modeled to obtain separate variances in anthropometry for each wealth quintile and education level. All analyses were stratified by survey year and sex.

RESULTS

On average, the positive socioeconomic gradient in adult's BMI and height persisted over time with slight attenuation. The residual variance in BMI ranged from 10.1 to 14.9 (7.2-11.3) by education level and 6.1 to 17.4 (5.0-13.0) by household wealth for women (men) in 2006, and they increased over time for the lower socioeconomic groups but remained the same or decreased for the higher socioeconomic groups. No significant pattern was observed for variation in height for both genders.

CONCLUSIONS

We found potential reversal in the socioeconomic patterning in BMI variability in India as suggested by the increasing dispersion among the least educated and poorest populations. For a comprehensive understanding of nutrition transition in developing countries, it is necessary to assess the changes in means and variances of anthropometry in tandem.

Racial and Ethnic Differences in Obesity in People With Spinal Cord Injury: The Effects of Disadvantaged Neighborhood

OBJECTIVE

To examine the role of neighborhood in the relation between race and obesity in people with spinal cord injury (SCI).

DESIGN

A cross-sectional analysis of survey data from National SCI Database linked with neighborhood data from American Community Survey by census tract.

SETTING

A total of 17 SCI Model Systems centers.

PARTICIPANTS

Individuals (N=3385; 2251 non-Hispanic whites, 760 non-Hispanic blacks, 374 Hispanics) who completed a follow-up assessment during 2006-2017 (mean duration of injury, 8.3±9.9y) and resided in 2934 census tracts.

INTERVENTION

Not applicable.

MAIN OUTCOME MEASURES

Body mass index (BMI) (kg/m2).

RESULTS

The overall prevalence of obesity was 52.9% (BMI≥25.0) and 23.3% (BMI≥30.0). Hispanics were 67.0% more likely to be obese (BMI≥30.0 kg/m2) relative to non-Hispanic whites (odds ratio, 1.67; 95% confidence interval, 1.27-2.18), after controlling for demographic and injury-related characteristics. Most of the non-Hispanic blacks (66.8%) were living in neighborhoods with high concentrated disadvantaged index (CDI), compared to 35.0% of Hispanics and 9.2% of non-Hispanic whites living in this similar neighborhood status (P<.0001). After accounting for CDI, the odds of being obese in Hispanics decreased (odds ratio, 1.51; 95% confidence interval, 1.15-1.99). Regardless of race and ethnicity, people with SCI from disadvantaged neighborhoods were 42.0%-70.0% more likely to be obese than those from minimal CDI neighborhoods.

CONCLUSIONS

Neighborhood characteristics partially diminish racial differences in obesity. Weight management for the SCI population should target those who are Hispanic and living in the disadvantaged neighborhoods.

Contribution of socioeconomic factors to the variation in body-mass index in 58 low-income and middle-income countries: an econometric analysis of multilevel data

BACKGROUND

Most epidemiological studies have not simultaneously quantified variance in health within and between populations. We aimed to estimate the extent to which basic socioeconomic factors contribute to variation in body-mass index (BMI) across different populations.

METHODS

We pooled data from the cross-sectional Demographic and Health Surveys (2005-16) for 15-49 year old women with complete data for anthropometric measures in 58 low-income and middle-income countries (LMICs). We compared estimates from multilevel variance component models for BMI before and after adjusting for age and socioeconomic factors (place of residence, education, household wealth, and marital status). The hierarchical structure of the sample included three levels with women at level 1, communities at level 2, and countries at level 3. The primary outcome was BMI. We did a sensitivity analysis using the 2002-03 World Health Surveys.

FINDINGS

Of 1 212 758 women nested within 64 764 communities and 58 countries, we found that most unexplained variation for BMI was attributed to between-individual differences (80%) and the remaining was between-population differences (14% for countries and 6% for communities). Socioeconomic factors explained a large proportion of between-population variance in BMI (14·8% for countries and 47·1% for communities), but only about 2% of interindividual variance. In country-specific models, we found substantial variation in the magnitude of between-individual differences (variance estimates ranging from 7·6 to 31·4, or 86·0-98·6% of the total variation) and the proportion explained by socioeconomic factors (0·1-6·4%). The disproportionately large unexplained between-individual variance in BMI was consistently found in additional analyses including more comprehensive set of predictor variables, both men and women, and populations from low-income and high-income countries.

INTERPRETATION

Our findings on variance decomposition in BMI and explanation by socioeconomic factors at population and individual levels indicate that inferential questions that target within and between populations are importantly inter-related and should be considered simultaneously.

FUNDING

None.

Change in the distribution of body mass index in Brazil: analysing the interindividual inequality between 1974 and 2013

BACKGROUND

Brazil is among the 10 countries with the highest prevalence of overweight in the world. The aim was to analyse the changes in the dispersion of body mass index (BMI) in the Brazilian population from the 1970s to 2013 in specific population groups.

METHODS

Data were extracted from five national household surveys between 1974-1975 and 2013, including adults aged 20 to 64. We calculated SD, median, fifth and 95th percentiles of BMI for each sociodemographic category (sex, age, schooling) and survey year in order to explore whether changes in mean BMI are followed by changes in dispersion.

RESULTS

During the period the mean BMI ranged from 22.7 kg/m² to 26.6 kg/m², with a much higher variation in the 95th percentile (+6.1 kg/m²) when compared with the fifth percentile (+1.8 kg/m²). The within-group differences increased over time. The SD increased in all categories analysed and was higher among women, lower schooling groups and the oldest group. An increase of 1.0 kg/m² in the BMI mean was associated with an increase of 0.32 kg/m² in the SD, 0.45 kg/m² in the fifth percentile and 1.50 kg/m² in the 95th percentile of BMI.

CONCLUSIONS

Population changes occurred in BMI are more complex than the simple increase of its average. Concomitant to the increase in BMI, there was an increase in the within-group differences, showing that growing inequalities are not driven solely by sociodemographic factors.

Baseline Body Mass Predicts Average Depressive Symptoms over the Next Two Decades for White but Not Black Older Adults

Background: Although obesity and depression have a bidirectional association, this link may vary based on race. The current study tested racial variation in bidirectional links between depressive symptoms and body mass index (BMI) over 24 years of follow-up in older adults over the age of 50 in the United States. We hypothesized weaker bidirectional links in Blacks compared to Whites. Methods: Data came from waves 1 to 12 (1990 to 2014) of the Health and Retirement Study (HRS), an ongoing state-of-the-art national cohort. The study followed a representative sample of Americans (n = 15,194; 2,200 Blacks and 12,994 Whites) over the age of 50. Dependent variables were average depressive symptoms and BMI over 24 years, based on measurements every other year, from 1990 to 2014. Independent variables included baseline depressive symptoms and BMI. Covariates included age, gender, marital status, veteran status, and activities of daily living. Structural equation models were fitted to the data for data analysis. Results: In the pooled sample, bidirectional associations were found between BMI and depressive symptoms as baseline BMI predicted average depressive symptoms over time and baseline depressive symptoms predicted average BMI over 24 years. Racial differences were found in the bidirectional association between BMI and depressive symptoms, with both directions of the associations being absent for Blacks. For Whites, baseline BMI predicted average depressive symptoms over the next 24 years. Conclusion: Reciprocal associations between BMI and depressive symptoms over a 24-year period among individuals over the age of 50 vary for Blacks and Whites. As these associations are stronger for Whites than Blacks, clinical and public health programs that simultaneously target comorbid obesity and depression may be more appropriate for Whites than Blacks.

Differences in magnitude and rate of change in adult obesity distribution by age and sex in Mexico, Colombia and Peru, 2005-2010

OBJECTIVE

Unequal obesity distributions among adult populations have been reported in low- and middle-income countries, but mainly based on data of women of reproductive age. Moreover, incorporation of ever-changing skewed BMI distributions in analyses has been a challenge. Our study aimed to assess magnitude and rates of change in BMI distributions by age and sex.

DESIGN

Shapes of BMI distributions were estimated for 2005 and 2010, and their changes were assessed, using the generalized additive model for location, scale and shape (GAMLSS) and assuming BMI follows a Box-Cox power exponential (BCPE) distribution.

SETTING

Nationally representative, repeated cross-sectional health surveys conducted between 2005 and 2013 in Mexico, Colombia and Peru.

SUBJECTS

Adult men and non-pregnant women aged 20-69 years.

RESULTS

Whereas women had more right-shifted and wider BMI distributions than men in almost all age groups across the countries in 2010, men in their 30s-40s experienced more rapid increases in BMI between 2005 and 2010, notably in Peru. The highest increase in overweight and obesity prevalence was observed among Peruvian men of 35-39 years, with a 5-year increase of 21 percentage points.

CONCLUSIONS

The BCPE-GAMLSS method is an alternative to analyse measurements with time-varying distributions visually, in addition to conventional indicators such as means and prevalences. Consideration of differences in BMI distributions and their changes by sex and age would provide vital information in tailoring relevant policies and programmes to reach target populations effectively. Increases in BMI portend increases of obesity-associated diseases, for which preventive and preparative actions are urgent.

Volumetric bone mineral density of the spine predicts mortality in African-American men with type 2 diabetes

The study showed that in African-American men with type 2 diabetes mellitus (T2D), vertebral volumetric bone mineral density (vBMD) predicts all-cause mortality, independent of other risk factors for death.

INTRODUCTION

Compared to European Americans, African Americans have lower rates of osteoporosis and higher rates of T2D. The relationships between BMD and fractures with mortality are unknown in this population. The aim of this study was to determine relationships between vertebral fractures and vertebral vBMD and mortality in African Americans with T2D.

METHODS

Associations between vertebral fractures and vBMD with all-cause mortality were examined in 675 participants with T2D (391 women and 284 men) in the African American-Diabetes Heart Study (AA-DHS). Lumbar and thoracic vBMD were measured using quantitative computed tomography (QCT). Vertebral fractures were assessed on sagittal CT images. Associations of vertebral fractures and vBMD with all-cause mortality were determined in sex-stratified analyses and in the full sample. Covariates in a minimally adjusted model included age, sex, BMI, smoking, and alcohol use; the full model was adjusted for those variables plus cardiovascular disease, hypertension, coronary artery calcified plaque, hormone replacement therapy (women), African ancestry proportion, and eGFR.

RESULTS

After mean 7.6 ± 1.8-year follow-up, 59 (15.1%) of women and 58 (20.4%) of men died. In men, vBMD was inversely associated with mortality in the fully adjusted model: lumbar hazard ratio (HR) per standard deviation (SD) = 0.70 (95% CI 0.52-0.95, p = 0.02) and thoracic HR per SD = 0.71 (95% CI 0.54-0.92, p = 0.01). Only trends toward association between vBMD and mortality were observed in the combined sample of men and women, as significant associations were absent in women. Vertebral fractures were not associated with mortality in either sex.

CONCLUSIONS

Lower vBMD was associated with increased all-cause mortality in African-American men with T2D, independent of other risk factors for mortality including subclinical atherosclerosis.

Association between population mean and distribution of deviance in demographic surveys from 65 countries: cross sectional study

OBJECTIVES

To examine whether conditions related to scarcity at the left side of the distribution (anaemia, severe chronic energy deficiency, and underweight) are as strongly related to population means as conditions of excess at the right side of the distribution (overweight and obesity).

DESIGN

Observational study.

SETTING

65 countries, with nationally representative cross sectional data from 1994 to 2014 obtained from the Demographic Health Surveys.

PARTICIPANTS

Non-pregnant women aged 20-49. Sample of 65 countries and n=524 380 for analysis of BMI; sample of 44 countries and n=316 465 for analysis of haemoglobin.

MAIN OUTCOME MEASURES

The association between mean and prevalence of each category. For BMI, prevalence of severe chronic energy deficiency (SCED, BMI <16.0), underweight (BMI <18.5), overweight (BMI >25) and obese (BMI >30.) were measured; for haemoglobin, prevalence of anaemia (haemoglobin <12.0 g/dL) and severe anaemia (haemoglobin <8.0 g/dL) were examined.

RESULTS

There was a strong association between mean BMI and prevalence of overweight (r²=0.98; r=0.99; β=8.3 (8.0 to 8.6)) and obesity (r²=0.93; r=0.97; β=4.2 (3.9 to 4.5)). For left sided conditions, a moderate to strong association was found between mean BMI and prevalence of underweight (r²=0.67; r=-0.82; β=-2.7 (-3.1 to -2.2)), and a weaker association for SCED (r²=0.38; r=-0.61; β=-0.32 (-0.43 to -0.22)). There was a moderate association between mean haemoglobin and prevalence of anaemia (r²=0.46; r=-0.68; β=-10.8 (-14.5 to -7.1)) and a weaker association with severe anaemia (r²=0.30; r=-0.55; β=-0.55 (-0.81 to -0.29)).

CONCLUSIONS

The associations between population means and prevalence of conditions of scarcity such as low BMI and anaemia were substantially weaker than the associations of mean BMI with conditions of excesses such as overweight and obesity.

Population-level trends in the distribution of body mass index in Canada, 2000-2014

OBJECTIVE

Research studying population-level body mass index (BMI) trends document increases in mean or prevalence of overweight/obese but less consideration has been given to describing the changing distribution of BMI. The objective of this research was to perform a detailed analysis of changes in the BMI distribution in Canada.

METHODS

Using data from the CCHS (2000-2014), we analyzed distributional parameters of BMI for 492,886 adults aged 25-64 years. We further stratified these analyses for women and men, education level, and region of residence.

RESULTS

Mean BMI has increased for most subgroups of the Canadian population. Mean BMI values were higher for men, while standard deviation (SD) of the BMI distribution was systematically higher in women. Increases in mean BMI were accompanied with increases in SD of BMI across cycles. Across survey cycles, the 95th percentile increased more than 10 times more rapidly compared to the 5th percentile, showing a very unequal change between extreme values in the BMI distribution over time. There was a relationship between SD with BMI, but these relations were generally not different between educational categories and regions. This suggests that the growing inter-individual inequalities (i.e., dispersion) in BMI were not solely attributable to socioeconomic and demographic factors.

CONCLUSIONS

This study supports the hypothesis that the simultaneous increases in mean BMI and SD of the BMI distribution are occurring, and suggests the need to move beyond the mean-centric paradigm when studying a complex public health phenomenon such as population change in BMI.

Obesity, underweight and BMI distribution characteristics of children by gross national income and income inequality: results from an international survey

BACKGROUND

Economic wealth and income inequality may impact on childhood BMI distribution by affecting overconsumption of food and sedentary forms of transportation and entertainment across the whole or some of the population.

OBJECTIVES

To determine whether BMI distribution of children differs by gross national income (GNI) per capita and Gini index derived from World Bank data.

METHODS

Secondary analysis of largely self-reported height and weight data from a multi-country, cross-sectional study (ISAAC), of 77,963 children aged 6-7 (from 19 countries) and 205,388 adolescents aged 13-14 (from 36 countries), were used to examine underweight vs obesity prevalence and BMI distribution skewness, median and dispersion.

RESULTS

Children and adolescents from 'lower' GNI countries had higher prevalence of underweight than those from 'higher' GNI countries (6% vs 3%, p = 0.03; 2% vs 1%, p = 0.05 respectively), but the prevalence of obesity was not different (2% vs 5%, p = 0.29; 2% vs 2%, p = 0.66). BMI distribution of participants from 'higher' GNI countries had higher median, without significant difference in skewness or dispersion compared to 'lower' GNI countries (higher medians +1.1 kg/m2 for 6-7 year olds, and + 0.7 kg/m2, +1.2 kg/m2 for 13-14 year old girls and boys respectively). Gini index was not associated with underweight or obesity prevalence in either children or adolescents, nor with any BMI distribution characteristics with one exception. Adolescent girls from higher income inequality countries had a greater median BMI (+0.7 kg/m2) and a less skewed BMI distribution.

CONCLUSIONS

It appears that the obesogenic impact of economic prosperity affects all children similarly. Income inequality may have a gender specific effect affecting BMI distribution in adolescent girls.

Changes in socio-economic level and their impact on nutritional status: a follow-up study among young Chilean adults

Objective

To verify the association between changes in socio-economic level (SEL) and nutritional status of Chilean adults over a 10-year period.

Design

Concurrent cohort study.

Setting/Subjects

Individuals born from 1974 to 1978 in the Valparaíso Region of Chile were evaluated between 2000 and 2002 (n 1232) and again between 2010 and 2012 (n 796). SEL was characterized according to the occupation and educational level of the head of household. Nutritional status was based on measurement of BMI and waist circumference (WC).

Results

Between the first and second evaluation there was a 13 % reduction in the number of individuals classified as poor and a 12 % increase in those classified in the medium high SEL. Increases in BMI were found among women who remained in the low SEL (β=2·2, 95 % CI 0·16, 2·87) compared with women who maintained the same SEL (and whose SEL was above low over the 10-year period). Women who remained in the low SEL increased their WC (β=4·10, 95 % CI 0·27, 7·93). There were no associations between nutritional status and SEL among males.

Conclusions

In the period studied, the SEL of the study population improved between the third and fourth decade of life, but BMI and WC also increased among women, with the lowest socio-economic group experiencing the greatest changes. Meanwhile, among males we found no association between anthropometric measurements and changes in SEL.

Distributional change of women's adult height in low- and middle-income countries over the past half century: An observational study using cross-sectional survey data

BACKGROUND

Adult height reflects childhood circumstances and is associated with health, longevity, and maternal-fetal outcomes. Mean height is an important population metric, and declines in height have occurred in several low- and middle-income countries, especially in Africa, over the last several decades. This study examines changes at the population level in the distribution of height over time across a broad range of low- and middle-income countries during the past half century.

METHODS AND FINDINGS

The study population comprised 1,122,845 women aged 25-49 years from 59 countries with women's height measures available from four 10-year birth cohorts from 1950 to 1989 using data from the Demographic and Health Surveys (DHS) collected between 1993 and 2013. Multilevel regression models were used to examine the association between (1) mean height and standard deviation (SD) of height (a population-level measure of inequality) and (2) median height and the 5th and 95th percentiles of height. Mean-difference plots were used to conduct a graphical analysis of shifts in the distribution within countries over time. Overall, 26 countries experienced a significant increase, 26 experienced no significant change, and 7 experienced a significant decline in mean height between the first and last birth cohorts. Rwanda experienced the greatest loss in height (-1.4 cm, 95% CI: -1.84 cm, -0.96 cm) while Colombia experienced the greatest gain in height (2.6 cm, 95% CI: 2.36 cm, 2.84 cm). Between 1950 and 1989, 24 out of 59 countries experienced a significant change in the SD of women's height, with increased SD in 7 countries-all of which are located in sub-Saharan Africa. The distribution of women's height has not stayed constant across successive birth cohorts, and regression models suggest there is no evidence of a significant relationship between mean height and the SD of height (β = 0.015 cm, 95% CI: -0.032 cm, 0.061 cm), while there is evidence for a positive association between median height and the 5th percentile (β = 0.915 cm, 95% CI: 0.820 cm, 1.002 cm) and 95th percentile (β = 0.995 cm, 95% CI: 0.925 cm, 1.066 cm) of height. Benin experienced the largest relative expansion in the distribution of height. In Benin, the ratio of variance between the latest and earliest cohort is estimated as 1.5 (95% CI: 1.4, 1.6), while Lesotho and Uganda experienced the greatest relative contraction of the distribution, with the ratio of variance between the latest and earliest cohort estimated as 0.8 (95% CI: 0.7, 0.9) in both countries. Limitations of the study include the representativeness of DHS surveys over time, age-related height loss, and consistency in the measurement of height between surveys.

CONCLUSIONS

The findings of this study indicate that the population-level distribution of women's height does not stay constant in relation to mean changes. Because using mean height as a summary population measure does not capture broader distributional changes, overreliance on the mean may lead investigators to underestimate disparities in the distribution of environmental and nutritional determinants of health.

Early childhood linear growth faltering in low-income and middle-income countries as a whole-population condition: analysis of 179 Demographic and Health Surveys from 64 countries (1993-2015)

BACKGROUND

The causes of early childhood linear growth faltering (known as stunting) in low-income and middle-income countries remain inadequately understood. We aimed to determine if the progressive postnatal decline in mean height-for-age Z score (HAZ) in low-income and middle-income countries is driven by relatively slow growth of certain high-risk children versus faltering of the entire population.

METHODS

Distributions of HAZ (based on WHO growth standards) were analysed in 3-month age intervals from 0 to 36 months of age in 179 Demographic and Health Surveys from 64 low-income and middle-income countries (1993-2015). Mean, standard deviation (SD), fifth percentiles, and 95th percentiles of the HAZ distribution were estimated for each age interval in each survey. Associations between mean HAZ and SD, fifth percentile, and 95th percentile were estimated using multilevel linear models. Stratified analyses were performed in consideration of potential modifiers (world region, national income, sample size, year, or mean HAZ in the 0-3 month age band). We also used Monte Carlo simulations to model the effects of subgroup versus whole-population faltering on the HAZ distribution.

FINDINGS

Declines in mean HAZ from birth to 3 years of age were accompanied by declines in both the fifth and 95th percentiles, leading to nearly symmetrical narrowing of the HAZ distributions. Thus, children with relatively low HAZ were not more likely to have faltered than taller same-age peers. Inferences were unchanged in surveys regardless of world region, national income, sample size, year, or mean HAZ in the 0-3 month age band. Simulations showed that the narrowing of the HAZ distribution as mean HAZ declined could not be explained by faltering limited to a growth-restricted subgroup of children.

INTERPRETATION

In low-income and middle-income countries, declines in mean HAZ with age are due to a downward shift in the entire HAZ distribution, revealing that children across the HAZ spectrum experience slower growth compared to the international standard. Efforts to mitigate postnatal linear growth faltering in low-income and middle-income countries should prioritise action on community-level determinants of childhood HAZ trajectories.

FUNDING

Bill & Melinda Gates Foundation.

Race-Ethnicity, Union Status, and Change in Body Mass Index in Young Adulthood

This study used data from three waves of the National Longitudinal Study of Adolescent to Adult Health (Add Health) and fixed-effects regression to consider whether associations between change in union status and change in BMI were moderated by race/ethnicity. The results indicated that intimate unions were differentially associated with gains in BMI along race/ethnic lines, especially for women. Compared to White women, marriage was associated with larger increases in BMI for Black, Hispanic and Multiracial women, and cohabitation was associated with larger increases for Black and Hispanic women. In contrast, both marriage and cohabitation were associated with less weight gain for Asian compared to White women. Among men, racial/ethnic differences in the relationship between union status and BMI were similarly patterned but less pronounced. The results suggest that, particularly for women, marital status-already its own source of stratification, further exacerbates racial/ethnic disparities in BMI from adolescence to young adulthood.

Illustrating a "consequential" shift in the study of health inequalities: a decomposition of racial differences in the distribution of body mass

PURPOSE

We present a conceptual introduction to "distributional inequalities"-differences in distributions of risk factors or other outcomes between social groups-as a consequential shift for research on health inequalities. We also review a companion analytical methodology, "distributional decomposition", which can assess the population characteristics that explain distributional inequalities.

METHODS

Using the 1999-2012 U.S. National Health and Nutrition Examination Survey, we apply statistical decomposition to (a) document gender-specific, black-white inequalities in the distribution of body mass index (BMI) and, (b) assess the extent to which demographic (age), socioeconomic (family income, education), and behavioral predictors (caloric intake, physical activity, smoking, alcohol consumption) are associated with broader distributional inequalities in BMI.

RESULTS

Black people demonstrate favorable or no different caloric intake, smoking, or alcohol consumption than whites, but worse levels of physical activity. Racial inequalities extend beyond the obesity threshold to the broader BMI distribution. Demographic, socioeconomic, and behavioral characteristics jointly explain more of the distributional inequality among men than women.

CONCLUSIONS

Black-white distributional inequalities are present both among men and women, although the mechanisms may differ by gender. The notion of "distributional inequalities" offers an additional purchase for studying social inequalities in health.

Patterning of individual heterogeneity in body mass index: evidence from 57 low- and middle-income countries

Modeling variation at population level has become increasingly valued, but no clear application exists for modeling differential variation in health between individuals within a given population. We applied Goldstein's method (in: Everrit, Howell (eds) Encyclopedia of statistics in behavioral science, Wiley, Hoboken, 2005) to model individual heterogeneity in body mass index (BMI) as a function of basic sociodemographic characteristics, each independently and jointly. Our analytic sample consisted of 643,315 non-pregnant women aged 15-49 years pooled from the latest Demographic Health Surveys (rounds V, VI, or VII; years 2005-2014) across 57 low- and middle-income countries. Individual variability in BMI ranged from 9.8 (95% CI: 9.8, 9.9) for the youngest to 23.2 (95% CI: 22.9, 23.5) for the oldest age group; 14.2 (95% CI: 14.1, 14.3) for those with no formal education to 19.7 (95% CI: 19.5, 19.9) for those who have completed higher education; and 13.6 (95% CI: 13.5, 13.7) for the poorest quintile to 20.1 (95% CI: 20.0, 20.2) for the wealthiest quintile group. Moreover, variability in BMI by age was also different for different socioeconomic groups. Empirically testing the fundamental assumption of constant variance and identifying groups with systematically large differentials in health experiences have important implications for reducing health disparity.

The statistical mechanics of human weight change

Over the past 35 years there has been a near doubling in the worldwide prevalence of obesity. Body Mass Index (BMI) distributions in high-income societies have increasingly shifted rightwards, corresponding to increases in average BMI that are due to well-studied changes in the socioeconomic environment. However, in addition to this shift, BMI distributions have also shown marked changes in their particular shape over time, exhibiting an ongoing right-skewed broadening that is not well understood. Here, we compile and analyze the largest data set so far of year-over-year BMI changes. The data confirm that, on average, heavy individuals become lighter while light individuals become heavier year-over-year, and also show that year-over-year BMI evolution is characterized by fluctuations with a magnitude that is linearly proportional to BMI. We find that the distribution of human BMIs is intrinsically dynamic-due to the short-term variability of human weight-and its shape is determined by a balance between deterministic drift towards a natural set point and diffusion resulting from random fluctuations in, e.g., diet and physical activity. We formulate a stochastic mathematical model for BMI dynamics, deriving a theoretical shape for the BMI distribution and offering a mechanism that may explain the right-skewed broadening of BMI distributions over time. An extension of the base model investigates the hypothesis that peer-to-peer social influence plays a role in BMI dynamics. While including this effect improves the fit with the data, indicating that correlations in the behavior of individuals with similar BMI may be important for BMI dynamics, testing social transmission against other plausible unmodeled effects and interpretations remains the subject of future work. Implications of our findings on the dynamics of BMI distributions for public health interventions are discussed.

Trends in the distribution of body mass index and waist circumference among South Korean adults, 1998-2014

BACKGROUND/OBJECTIVES

An increase in mean body mass index (BMI) or prevalence of obesity may be accompanied by changes in the population BMI distribution. This study aimed to examine how the distributions of BMI and waist circumference (WC) have changed in South Korea over a 16-year interval (1998-2014).

SUBJECTS/METHODS

Using the Korea National Health and Nutrition Examination Survey, we analyzed changes in mean, standard deviation (SD), 5th, and 95th percentile values of BMI and WC distributions for 46,343 (BMI) and 46,327 (WC) adults aged 25-64 years.

RESULTS

For men, mean BMI increased at an annual rate of 0.060 units (95% CI: 0.047-0.073) with annual increases of 0.029 units in SD (95% CI: 0.019-0.039), 0.121 units in the 95th percentile (95% CI: 0.097-0.145) and 0.042 units in the 5th percentile (95% CI: 0.021-0.062). The 95th percentile and SD of the WC distribution increased, but not mean WC and the 5th percentile. For women, mean BMI decreased at an annual rate of 0.030 units (95% CI: 0.010-0.049) with a 0.030-unit increase in SD (95% CI: 0.012-0.048) and a 0.049-unit decrease in the 5th percentile (95% CI: 0.029-0.070). Mean WC also decreased with an increase in SD and a decrease in the 5th percentile.

CONCLUSIONS

These findings suggest increasing dispersion in the distribution of BMI and WC derived from significant shifts in the upper tails for Korean men, but not women. Future research needs to identify the factors that underlie the increasing dispersion of obesity measures.

Racial Differences in Weight Gain: A 5-Year Longitudinal Study of Persons With Spinal Cord Injury

OBJECTIVE

To assess racial differences in body mass index (BMI) change over 5 years among people with spinal cord injury (SCI).

DESIGN

Multicenter longitudinal study.

SETTING

Spinal Cord Injury Model Systems centers.

PARTICIPANTS

Individuals (N=437; 313 non-Hispanic white, 81 non-Hispanic black, and 43 Hispanic; 335 men; mean age, 41.3±13.5y) who incurred an SCI from 1974 to 2010 and completed 2 follow-up assessments within 5 years between October 1, 2006 and September 18, 2015 (mean duration of injury, 9.1±9.6y at the start of the 5-year follow-up).

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

BMI (in kilograms per meters squared).

RESULTS

The mean BMI of 437 participants increased from 26.4±6.3 to 27.0±6.4kg/m² over 5 years (P=.002). The greatest increase was noted for Hispanics (2.0±5.7kg/m²; P=.02), followed by non-Hispanic whites (0.6±3.9kg/m²; P=.01) and non-Hispanic blacks (0.01±3.7kg/m²; P>.99). The differences in BMI increase across racial groups were significant (P=.03) in those with paraplegia (American Spinal Injury Association Impairment Scale A, B or C), those who were underweight or of normal weight at baseline, and those within 10 years of their injury. Such racial differences remained significant after taking into account demographic and injury characteristics.

CONCLUSIONS

Our study findings provide a foundation for future research to explore risk and protective factors that contribute to racial differences in weight gain after SCI, which help alert health care professionals to a high-risk group for obesity prevention and management.

Secular Trends in the Physical Fitness of United States Army Recruits on Entry to Service, 1975-2013

Knapik, JJ, Sharp, MA, and Steelman, RA. Secular trends in the physical fitness of United States Army recruits on entry to service, 1975-2013. J Strength Cond Res 31(7): 2030-2052, 2017-A systematic literature search was conducted to identify and analyze articles that reported on physical fitness of new US Army recruits. The National Library of Medicine's PubMed and the Defense Technical Information Center were searched using the keywords (military personnel OR trainee OR recruit OR soldier) AND (physical fitness OR strength OR endurance OR flexibility OR balance OR coordination OR muscle contraction OR running OR exercise OR physical conditioning). Reference lists of obtained articles and contact with authors enhanced the search. Studies were selected if they involved recruits in Basic Combat Training or One-Station Unit Training, provided a quantitative assessment of at least one fitness measure, and the fitness measure(s) were obtained early in training. Average values for each fitness measure were obtained, plotted by the year of data collection, and fitted to linear regression models (fitness measure × year). Fifty-three articles met the review criteria. Regression analysis indicated little temporal change in height, but body weight, body mass index, body fat, and fat-free mass increased over time. Limited V[Combining Dot Above]O2max data suggested no temporal change in male recruits, but those in female recruits V[Combining Dot Above]O2max seem to have slightly improved. Apparently contradicting the V[Combining Dot Above]O2max findings, performance on endurance runs (1- and 2-mile) declined, possibly because of the increase in body weight. Muscular endurance (push-ups, sit-ups) demonstrated little systematic change over time. Limited but multiple measures of muscular strength suggest a temporal increase in strength. Specific components of US Army recruit fitness seem to have changed over time.

The Weight of Inequality: Socioeconomic Status and Adolescent Body Mass in Brazil

The high rate of obesity among adolescents is a global public health problem that has recently expanded to affect middle- and low-income countries. Brazil, which is undergoing a relatively rapid nutrition transition and has inadequate health systems, is currently experiencing the consequences of increasing rates of overweight and obesity concomitantly with the consequences of generations of malnourishment. Given this scenario, Brazil is an ideal context for examining the relationship between family socioeconomic status (SES) and adolescent body mass, as well as how this relationship varies across very different regions within the same country and across the body mass index (BMI) continuum. Guided by a framework that integrates nutrition transition and fundamental cause theories, we use unique nationally representative data with measured height and weight for all household members to conduct quantile regression models. The results suggest that family socioeconomic conditions are important theoretical factors associated with adolescent BMI, but that the way in which family SES impinges on adolescent BMI varies across regions characterized by different locations in the nutrition transition and varying levels of economic development. We also find that family socioeconomic disadvantages operate very differently according to BMI status. The results show that the socioeconomic gradient of adolescent BMI varies by stages of the nutrition transition and economic development and across BMI percentiles.

Sustained Obesity and Depressive Symptoms over 6 Years: Race by Gender Differences in the Health and Retirement Study

Background: Although obesity and physical activity influence psychosocial well-being, these effects may vary based on race, gender, and their intersection. Using 6-year follow-up data of a nationally representative sample of adults over age of 50 in the United States, this study aimed to explore race by gender differences in additive effects of sustained high body mass index (BMI) and physical activity on sustained depressive symptoms (CES-D) and self-rated health (SRH).

Methods: Data came from waves 7, 8, and 10 (2004–2010) of the Health and Retirement Study (HRS), an ongoing national cohort started in 1992. The study enrolled a representative sample of Americans (n = 19,280) over the age of 50. Latent factors were used to calculate sustained high BMI and physical activity (predictors) and sustained poor SRH and high depressive symptoms (outcomes) based on measurements in 2004, 2006, and 2010. Age, education, and income were confounders. Multi-group structural equation modeling (SEM) was used to test the additive effects of BMI and physical activity on depressive symptoms and SRH, where the groups were defined based on race by gender.

Results: Group differences were apparent in the direction and significance of the association between sustained high BMI and depressive symptoms. The association between sustained high BMI and depressive symptoms was positive and significant for White women (B = 0.03, p = 0.007) and non-significant for White men (B = −0.03, p = 0.062), Black men (B = −0.02, p = 0.564) and Black women (B = 0.03, p = 0.110). No group differences were found in the paths from sustained physical activity to depressive symptoms, or from physical activity or BMI to SRH.

Conclusion: Sustained high BMI and high depressive symptoms after age 50 are positively associated only for White women. As the association between sustained health problems such as depression and obesity are not universal across race and gender groups, clinical and public health interventions and programs that simultaneously target multiple health problems may have differential effects across race by gender groups.

Socioeconomic Inequalities in Body Mass Index across Adulthood: Coordinated Analyses of Individual Participant Data from Three British Birth Cohort Studies Initiated in 1946, 1958 and 1970

BACKGROUND

High body mass index (BMI) is an important contributor to the global burden of ill-health and health inequality. Lower socioeconomic position (SEP) in both childhood and adulthood is associated with higher adult BMI, but how these associations have changed across time is poorly understood. We used longitudinal data to examine how childhood and adult SEP relates to BMI across adulthood in three national British birth cohorts.

METHODS AND FINDINGS

The sample comprised up to 22,810 participants with 77,115 BMI observations in the 1946 MRC National Survey of Health and Development (ages 20 to 60-64), the 1958 National Child Development Study (ages 23 to 50), and the 1970 British Cohort Study (ages 26 to 42). Harmonized social class-based SEP data (Registrar General's Social Class) was ascertained in childhood (father's class at 10/11 y) and adulthood (42/43 years), and BMI repeatedly across adulthood, spanning 1966 to 2012. Associations between SEP and BMI were examined using linear regression and multilevel models. Lower childhood SEP was associated with higher adult BMI in both genders, and differences were typically larger at older ages and similar in magnitude in each cohort. The strength of association between adult SEP and BMI did not vary with age in any consistent pattern in these cohorts, but were more evident in women than men, and inequalities were larger among women in the 1970 cohort compared with earlier-born cohorts. For example, mean differences in BMI at 42/43 y amongst women in the lowest compared with highest social class were 2.0 kg/m2 (95% CI: -0.1, 4.0) in the 1946 NSHD, 2.3 kg/m2 (1.1, 3.4) in the 1958 NCDS, and 3.9 kg/m2 (2.3, 5.4) the in the 1970 BCS; mean (SD) BMI in the highest and lowest social classes were as follows: 24.9 (0.8) versus 26.8 (0.7) in the 1946 NSHD, 24.2 (0.4) versus 26.5 (0.4) in the 1958 NCDS, and 24.2 (0.3) versus 28.1 (0.8) in the 1970 BCS. Findings did not differ whether using overweight or obesity as an outcome. Limitations of this work include the use of social class as the sole indicator of SEP-while it was available in each cohort in both childhood and adulthood, trends in BMI inequalities may differ according to other dimensions of SEP such as education or income. Although harmonized data were used to aid inferences about birth cohort differences in BMI inequality, differences in other factors may have also contributed to findings-for example, differences in missing data.

CONCLUSIONS

Given these persisting inequalities and their public health implications, new and effective policies to reduce inequalities in adult BMI that tackle inequality with respect to both childhood and adult SEP are urgently required.

Risk of Recurrence and Mortality in a Multi-Ethnic Breast Cancer Population

BACKGROUND

Compared to non-Hispanic whites, African-American women tend to be diagnosed with breast cancer at an earlier age, to have less favorable tumor characteristics, and to have poorer outcomes from breast cancer. The extent to which differences in clinical characteristics account for the black/white disparity in breast cancer mortality is unclear. The purpose of this investigation was to examine the association of clinical, demographic, and treatment variables with total mortality and breast cancer recurrence by race/ethnicity in a cohort of women diagnosed with invasive breast cancer.

METHODS

To this end, we used data on 3890 invasive breast cancer cases diagnosed at a single medical center. Cox proportional hazards models were used to estimate hazard ratios (HR) and 95% confidence intervals (95% CI) for the association of tumor characteristics and treatment variables with mortality and recurrence.

RESULTS

Compared to white women, black women with breast cancer presented with tumors that had worse prognostic factors, particularly higher stage, lower frequency of hormone-receptor positive tumors, and higher frequency of comorbidities. Hispanics also generally had less favorable prognostic factors compared to non-Hispanic whites. Among estrogen receptor-positive cases, blacks had roughly a two-fold increased risk of recurrence compared to non-Hispanic whites. However, ethnicity/race was not associated with total mortality. Tumor stage, tumor size, and Charlson comorbidity index were positively associated with mortality, and mammography and chemotherapy and hormone therapy were inversely associated with mortality.

CONCLUSION

In spite of poorer prognostic factors among blacks compared whites, race/ethnicity was not associated with total mortality in our study.

The idea of uniform change: is it time to revisit a central tenet of Rose's "Strategy of Preventive Medicine"?

A mean-centric view of populations, whereby a change in the mean of a health variable at the population level is assumed to result in uniform change across the distribution, is a core component of Geoffrey Rose's concept of the "population strategy" to disease prevention. This idea also has a critical role in Rose's observation that individuals who are considered abnormal or sick (the rightward tail of the distribution) and those who are considered normal (the center) are very closely related, and that true preventive medicine must focus on shifting the normal or average. In this Perspective, we revisit these core tenets of Rose's concept of preventive medicine after providing an overview of the key concepts that he developed. We examine whether these assumptions apply to population changes in body mass index (BMI) and show that there is considerable evidence of a widening of the BMI distribution in populations over time. We argue that, with respect to BMI, the idea of using statistical measures of a population solely on the basis of means and the assumption that populations are coherent entities that change uniformly over time may not fully capture the true nature of changes in the population. These issues have important implications for how we assess and interpret the health of populations over time with implications for the balance between universal and targeted strategies aimed at improving health.

Inter-individual inequality in BMI: An analysis of Indonesian Family Life Surveys (1993-2007)

Widening inequalities in mean Body Mass Index (BMI) between social and economic groups are well documented. However, whether changes in mean BMI are followed by changes in dispersion (or variance) and whether these inequalities are also occurring within social groups or across individuals remain understudied. In addition, a substantial body of literature exists on the global increase in mean BMI and prevalence of overweight and obesity. However, whether this weight gain is shared proportionately across the whole spectrum of BMI distribution, also remains understudied. We examined changes in the distribution of BMI at the population level over time to understand how changes in the dispersion reflect between-group compared to within-group inequalities in weight gain. Moreover, we investigated the entire distribution of BMI to determine in which percentiles the most weight gain is occurring over time. Utilizing four waves (from 1993 to 2007) of Indonesian Family Life Surveys (IFLS), we estimated changes in the mean and the variance of BMI over time and across various socioeconomic groups based on education and households' expenditure per capita in 53,648 men and women aged 20-50 years. An increase in mean and standard deviation was observed among men (by 4.3% and 25%, respectively) and women (by 7.3% and 20%, respectively) over time. Quantile-Quantile plots showed that higher percentiles had greater increases in BMI compared to the segment of the population at lower percentiles. While between socioeconomic group differences decreased over time, within-group differences increased and were more prominent among individuals with poor education and lower per capita expenditures. Population changes in BMI cannot be fully described by average trends or single parameters such as the mean BMI. Moreover, greater increases in within-group dispersion compared with between-group differences imply that growing inequalities are not merely driven by these socioeconomic factors at the population level.

Fresh Start, a postpartum weight loss intervention for diverse low-income women: design and methods for a randomized clinical trial

BACKGROUND

Overweight and obesity are prevalent among young women and are greater among minority and low-income women. The postpartum period is critical in women's weight trajectories as many women do not lose their pregnancy weight, and others lose some and then plateau or experience weight gain. Excess weight puts women at greater risk of chronic disease and thus weight loss in the postpartum period may be key to the long-term health of young women. This paper describes the design and methods of a randomized clinical trial of Fresh Start, an innovative narrative-based group intervention aimed at promoting postpartum weight loss among low-income, diverse women.

METHODS/DESIGN

Study participants were recruited from the five sites of the Women, Infants and Children (WIC) program in central Massachusetts. Participants were English-speaking, age ≥ 18 years, 6 weeks to 6 months postpartum, with a body mass index (BMI) ≥ 27 kg/m(2). The Fresh Start postpartum weight loss intervention, adapted from the Diabetes Prevention Program (DPP) in collaboration with WIC staff and clients, consisted of an 8-week group-based curriculum followed by nine monthly telephone calls. It included a narrative component (i.e., storytelling), group discussions, print materials and access to exercise facilities. The study is a two-arm randomized controlled trial. The control condition included print materials and access to exercise facilities. In-person assessments were conducted at baseline and at 6 and 12 months following the eight-week intervention phase.

DISCUSSION

The Fresh Start intervention translated key elements of an evidence-based weight loss protocol into a format that is hypothesized to be relevant, acceptable and effective for the target audience of low-SES postpartum women. This novel intervention was developed in collaboration with WIC to be sustainable within the context of its clinics, which reach approximately 9 million individuals per year across the U.S. via 10,000 clinics.

TRIAL REGISTRATION

clinicaltrials.gov NCT02176915 . Registered 25 June 2014.

The Association Between Blood Mercury Levels and Risk for Overweight in a General Adult Population: Results from the Korean National Health and Nutrition Examination Survey

The primary objective of this study was to estimate the association between blood mercury levels and overweight in Korean adults. We analyzed cross-sectional data from 9228 participants (4283 men and 4945 women) who completed the Korean National Health and Nutrition Examination Survey (KNHANES), 2007-2013. The population was divided into two groups according to the body mass index (BMI) and waist circumference (WC). Blood mercury levels were analyzed using a gold amalgam method with a DMA-80 instrument, categorized into quartiles, and stratified by sex. After adjusting for all covariates, blood mercury was significantly associated with overweight in all subjects. According to the BMI criteria, the adjusted odds ratio of being in the highest blood mercury quartile was 1.75 (95 % confidence interval [CI], 1.53-2.01) overall, 2.09 (95 % CI, 1.71-2.55) in men, and 1.58 (95 % CI, 1.32-1.89) in women. According to the WC criteria, the adjusted odds ratio of being in the highest blood mercury quartile was 1.85 (95 % CI, 1.49-2.30) in men and 1.96 (95 % CI, 1.62-2.36) in women compared to the lowest quartile. Additionally, a trend in overweight across increasing blood mercury levels was observed by the p for trend test in the multiple diagnostic criteria.

Population-level trends in the distribution of body mass index in England, 1992-2013

BACKGROUND

Changes over time of mean body weight or prevalence of overweight and obesity have been well documented. Less consideration has been given to describing the distribution to these changes particularly by socioeconomic status and sex.

METHODS

We use data from the Health Survey for England for the years 1992-2013 to calculate the median, 5th and 95th centiles, and SD of body mass index (BMI). We tested differences using analysis of variance and quantile regression. Analyses were stratified by sex and level of education.

RESULTS

There have been increases in the SD of BMI values over the period. While median BMI has increased, there has been a larger increase of the 95th centile. These trends were consistent by sex and level of education, although significant differences were observed in values.

CONCLUSIONS

Our results demonstrate that changes in median BMI over time do not reflect changes in the distribution of BMI. Failing to understand the distribution of body weight in the population will hamper our projections of future patterns, as well as our ability to design effective public health strategies.