Gender‐ethnic Disparity in BMI and Waist Circumference Distribution Shifts in US Adults

While obesity has been increasing in the United States, little is known about the variation in recent BMI and waist circumference (WC) distribution shifts across socio‐demographic groups. We assessed shifts in BMI and WC distributions and compared between‐group differences over the past decade, and projected future BMI and WC distributions and prevalence of obesity and central obesity using National Health and Nutrition Examination Survey (NHANES) 1988–1994 and 1999–2004 data. BMI/WC distributional shifts overall and in percentiles were compared across groups. Average yearly shift was calculated and used for projecting future distributions and prevalence. Both BMI and WC increased more in their uppermost percentile distribution, though BMI shift declined toward the uppermost percentiles among women. Heavier Americans gained more adiposity over the past decade. Ethnic (non‐Hispanic (NH) white vs. black) disparities in mean BMI and WC became wider. Over the survey period, mean BMI increased by 1.3 units vs. 1.8 units among men and women, whereas WC, by 4.2 cm vs. 4.8 cm. Young adults had the largest increase. Shift in women's WC was stable between the 25th and 75th percentiles, but gained pace at higher WC, while women's BMI and men's BMI and WC shifts increased linearly. NH black women had the largest shifts and would have central obesity and obesity prevalence of 90.8 and 70.7% by 2020. Shifts in BMI and WC distribution varied across age‐, gender‐, and ethnic groups. Future rise in the obesity and central obesity prevalence rates are expected, but would vary by demographic groups.     

BMI and All‐cause Mortality Among Japanese Older Adults: Findings From the Japan Collaborative Cohort Study

The association between BMI and all‐cause mortality may vary with gender, age, and ethnic groups. However, few prospective cohort studies have reported the relationship in older Asian populations. We evaluated the association between BMI and all‐cause mortality in a cohort comprised 26,747 Japanese subjects aged 65–79 years at baseline (1988–1990). The study participants were followed for an average of 11.2 years. Proportional‐hazards regression models were used to estimate mortality hazard ratios (HRs) and 95% confidence intervals. Until 2003, 9,256 deaths occurred. The underweight group was associated with a statistically higher risk of all‐cause mortality compared with the mid‐normal‐range group (BMI: 20.0–22.9); resulting in a 1.78‐fold (95% confidence interval: 1.45–2.20) and 2.55‐fold (2.13–3.05) increase in mortality risk among severest thin men and women (BMI: <16.0), respectively. Even within the normal‐range group, the lower normal‐range group (BMI: 18.5–19.9) showed a statistically elevated risk. In contrast, being neither overweight (BMI: 25.0–29.9) nor obese (BMI: ≥30.0) elevated the risk among men; however among women, HR was slightly elevated in the obese group but not in the overweight group compared with the mid‐normal‐range group. Among Japanese older adults, a low BMI was associated with increased risk of all‐cause mortality, even among those with a lower normal BMI range. The wide range of BMI between 20.0 and 29.9 in both older men and women showed the lowest all‐cause mortality risk.     

Anticipated Survival and Health Behaviours in Older English Adults: Cross Sectional and Longitudinal Analysis of the English Longitudinal Study of Ageing

Background

Individuals may make a rational decision not to engage in healthy behaviours based on their assessment of the benefits of such behaviours to them, compared to other uncontrollable threats to their health. Anticipated survival is one marker of perceived uncontrollable threats to health. We hypothesised that greater anticipated survival: a) is cross-sectionally associated with healthier patterns of behaviours; b) increases the probability that behaviours will be healthier at follow up than at baseline; and c) decreases the probability that behaviours will be ‘less healthy’ at follow than at baseline.

Methods

Data from waves 1 and 5 of the English Longitudinal Survey of Ageing provided 8 years of follow up. Perceptions of uncontrollable threats to health at baseline were measured using anticipated survival. Health behaviours considered were self-reported cigarette smoking, physical activity level, and frequency of alcohol consumption. A wide range of socio-economic, demographic, and health variables were adjusted for.

Results

Greater anticipated survival was cross-sectionally associated with lower likelihood of smoking, and higher physical activity levels, but was not associated with alcohol consumption. Lower anticipated survival was associated with decreased probability of adopting healthier patterns of physical activity, and increased probability of becoming a smoker at follow up. There were no associations between anticipated survival and change in alcohol consumption.

Conclusions

Our hypotheses were partially confirmed, though associations were inconsistent across behaviours and absent for alcohol consumption. Individual assessments of uncontrollable threats to health may be an important determinant of smoking and physical activity.     

Relationship of BMI,Waist Circumference,and Weight Change with Use of Health Services by Older Adults

Objective: To examine the relationship of BMI, waist circumference (WC), and weight change with use of health care services by older adults. Research Methods and Procedures: This was a prospective cohort study conducted from 2001 to 2003 among 2919 persons representative of the non‐institutionalized Spanish population ≥60 years of age. Analyses were performed using logistic regression, with adjustment for age, educational level, size of place of residence, tobacco use, alcohol consumption, and presence of chronic disease. Results: Obesity (BMI ≥ 30 kg/m²) and abdominal obesity (WC >102 cm in men and >88 cm in women) in 2001 were associated with greater use of certain health care services among men and women in the period 2001–2003. Compared with women with WC ≤ 88 cm, women with abdominal obesity were more likely to visit primary care physicians [odds ratio (OR): 1.36; 95% confidence limit (CL): 1.06–1.73] and receive influenza vaccination (OR: 1.30; 95% CL: 1.03–1.63). Weight gain was not associated with greater health service use by either sex, regardless of baseline BMI. Weight loss was associated with greater health service use by obese and non‐obese subjects of both sexes. In comparison with those who reported no important weight change, non‐obese women who lost weight were more likely to visit hospital specialists (OR: 1.45; 95% CL: 1.02–2.06), receive home medical visits (OR: 1.61; 95% CL: 1.06–2.45), be hospitalized (OR: 1.88; 95% CL: 1.29–2.74), and have more than one hospital admission (OR: 2.31; 95% CL: 1.19–4.47). Discussion: Obesity and weight loss are associated with greater health service use among the elderly.     

Development of Health‐Related Waist Circumference Thresholds Within BMI Categories

Objective: To develop and cross‐validate waist circumference (WC) thresholds within BMI categories. The utility of the derived values was compared with the single WC thresholds (women, 88 cm; men, 102 cm) recommended by NIH and Health Canada. Research Methods and Procedures: The sample included adults classified as normal weight (BMI = 18.5 to 24.9), overweight (BMI = 25 to 29.9), obese I (BMI = 30 to 34.9), and obese II+ (BMI ≥ 35) from the Third U.S. National Health and Nutrition Examination Survey (NHANES III; n = 11, 968) and the Canadian Heart Health Surveys (CHHS; n = 6286). Receiver operating characteristic curves were used to determine the optimal WC thresholds that predicted high risk of coronary events (top quintile of Framingham scores) within BMI categories using the NHANES III. The BMI‐specific WC thresholds were cross‐validated using the CHHS. Results: The optimal WC thresholds increased across BMI categories from 87 to 124 cm in men and from 79 to 115 cm in women. The validation study indicated improved sensitivity and specificity with the BMI‐specific WC thresholds compared with the single thresholds. Discussion: Compared with the recommended WC thresholds, the BMI‐specific values improved the identification of health risk. In normal weight, overweight, obese I, and obese II+ patients, WC cut‐offs of 90, 100, 110, and 125 cm in men and 80, 90, 105, and 115 cm in women, respectively, can be used to identify those at increased risk.     

Waist Circumference and Abdominal Obesity among Older Adults: Patterns,Prevalence and Trends

Objectives

To describe the patterns and trends in waist circumference and abdominal obesity for those aged 70–89 contrasting the standard and new age-related cut-points, and to investigate how they vary with time, age and educational level.

Methods

The subjects were 7129 men and 9244 women aged 70–89 years who participated in the Health Survey for England during 1993–2010. The outcome measures were the percentiles of waist circumference and standard and new indicators of abdominal obesity based on waist circumference. Binomial and quantile regression were used to investigate the relationship with key explanatory variables.

Results

The distribution of waist circumference among community-dwelling older adults in England has shifted upwards since 1993 (an increase in median of 4.5 cm in men and 5.1 cm in women). The prevalence of abdominal obesity has increased, while those in the low-risk group have decreased. Abdominal obesity was higher in those aged 70–79 compared to 80–89, and in those who left education earlier. The prevalence of abdominal obesity varies considerably with new and standard cut-points, which makes it impractical to use the new ones on a population that includes subjects across the adult age range.

Conclusions

Obesity is increasing among the elderly, but more work is needed on devising age-appropriate indicators of high risk based on waist circumference.     

Waist Circumference is an Independent Correlate of Errors in Self‐Reported BMI

Although there are issues of reporting bias surrounding the use of self‐reported BMI, it is frequently the method employed to establish the prevalence of obesity. The goal of this study was to assess whether, independently of measured BMI, waist circumference (WC) was associated with the magnitude of the difference between self‐reported and measured BMI within a large sample of European‐American (EA) and African‐American (AA) adults. Self‐reported height and weight, and measured height, weight, and WC were collected on 12,809 adults (61% women, 66% EA) aged 18–65 years. Mean negative BMI differences (self‐reported minus measured BMI) were identified in all race‐by‐sex groups (AA men: ?0.55; EA men: ?0.63; AA women: ?0.91; EA women: ?0.67). WC was negatively associated with the BMI difference such that a higher WC was associated with greater under‐reporting of BMI. However, after adjusting for age and measured BMI, WC was positively associated with the BMI difference in all race‐by‐sex groups. These results suggest that WC could be useful in gaining an insight into people's awareness of their own body size and fatness.     

BMI and Mortality: Results From a National Longitudinal Study of Canadian Adults

Although a clear risk of mortality is associated with obesity, the risk of mortality associated with overweight is equivocal. The objective of this study is to estimate the relationship between BMI and all‐cause mortality in a nationally representative sample of Canadian adults. A sample of 11,326 respondents aged ≥25 in the 1994/1995 National Population Health Survey (Canada) was studied using Cox proportional hazards models. A significant increased risk of mortality over the 12 years of follow‐up was observed for underweight (BMI <18.5; relative risk (RR) = 1.73, P < 0.001) and obesity class II+ (BMI >35; RR = 1.36, P <0.05). Overweight (BMI 25 to <30) was associated with a significantly decreased risk of death (RR = 0.83, P < 0.05). The RR was close to one for obesity class I (BMI 30–35; RR = 0.95, P >0.05). Our results are similar to those from other recent studies, confirming that underweight and obesity class II+ are clear risk factors for mortality, and showing that when compared to the acceptable BMI category, overweight appears to be protective against mortality. Obesity class I was not associated with an increased risk of mortality.     

BMI,Waist Circumference,and Mortality According to Health Status in the Older Adult Population of Spain

Among the explanations proposed for the weak and inconsistent association between BMI and mortality in the elderly are the lack of adjustment for waist circumference (WC) and that the association varies with health status. This work examines the independent association of BMI and WC with mortality in older adults, and the influence of health status on this association. A cohort of 3,536 persons representative of the Spanish population aged ≥60 years was selected in 2000 and 2001, and followed prospectively until 2007. The analyses were performed with Cox models and adjusted for the main confounders. During follow‐up, 659 persons died (18.6% of the cohort). Before adjusting for WC, mortality in the upper quartile of BMI was 15% lower than in the lower quartile (hazard ratio (HR): 0.85; 95% confidence interval (CI): 0.66–1.08; P for linear trend = 0.076). After adjusting for WC, the association was even stronger, so that mortality in the upper quartile of BMI was 37% lower than in the lower quartile (HR: 0.63; 95% CI: 0.45–0.88; P for linear trend < 0.003). Before adjusting for BMI, no association was observed between WC and mortality. After adjusting for BMI, WC was positively associated with mortality (HR for upper vs. lower quartile of WC: 1.48; 95% CI: 1.07–2.05; P for linear trend = 0.008). These associations were mainly observed in those with limitations in mobility and agility. BMI has an inverse, and WC has a direct, independent association with mortality in older adults, particularly in those with worse health status.     

Waist Circumference,BMI, Smoking,and Mortality in Middle‐Aged Men and Women

Objective: Measurement of waist circumference alone as a proxy of abdominal fat mass has been suggested as a simple clinical alternative to BMI for detecting adults with possible health risks due to obesity. Research Methods and Procedures: From 1993 to 1997, 27, 178 men and 29, 875 women, born in Denmark, 50 to 64 years of age, were recruited in the Danish prospective study Diet, Cancer and Health. By the end of the year 2000, 1465 deaths had occurred. We evaluated the relationship between waist circumference and BMI (simultaneously included in the model) and all‐cause mortality. We used Cox regression models to estimate the mortality‐rate ratios and to consider possible confounding from smoking. Results: Waist circumference among both men and women showed a strong dose‐response type of relationship with mortality when adjusted for BMI, whereas the low range of BMI was inversely associated with mortality when adjusted for waist circumference. A 10% larger waist circumference corresponded to a 1.48 (95% confidence interval: 1.36 to 1.61) times higher mortality over the whole range of waist circumference. The associations were independent of age and time since baseline examination. Restriction to never smokers showed a similar pattern, but a weakening of the associations. Discussion: Despite the high correlation between waist circumference and BMI, the combination may be very relevant in clinical practice because waist circumference for given BMI was a strong predictor of all‐cause mortality. The inverse association between BMI and mortality for given waist circumference was diminished in never smokers, particularly for high values of BMI.     

Levothyroxine Dosing in Older Adults: Recommendations Derived From The Baltimore Longitudinal Study of Aging

ObjectiveAs thyroid hormone metabolism slows with advancing age, treatment dosing requirements change. Guidelines recommend titration from a low starting dose for older adults with hypothyroidism while providing weight-based estimates for younger populations. However, rapid replacement may be appropriate with acute onset of overt hypothyroidism. Therefore, a weight-based recommendation specific to older adults is needed.MethodsWe determined mean levothyroxine dose using actual and ideal body weight (IBW) ratios for the outcome of euthyroid on therapy relative to assay-specific and proposed age-specific ranges for independently living participants aged ≥65 years in the Baltimore Longitudinal Study of Aging. We examined risk factors to identify those at highest risk of overtreatment using regression analyses adjusted for potential covariables and clustering to account for multiple visits per individual.ResultsOne hundred eighty-five participants aged ≥65 years were on levothyroxine at 645 eligible visits. At euthyroid visits, participants were on an average dose of 1.09 μg/kg (1.35 μg/kg IBW), with 84% of euthyroid individuals on a dose of <1.6 μg/kg. Average euthyroid dose did not differ by sex using either actual body weight (ABW) or IBW. For obese individuals, mean euthyroid dose was lower if calculated using ABW (0.9 μg/kg vs 1.14 μg/kg; P < .01) but similar if calculated using IBW (1.42 vs 1.32 μg/kg IBW; P = .41) compared with those with a body mass index of <30.ConclusionThyroid hormone dose per body weight estimates for replacement in older adults (1.09 μg/kg ABW or 1.35 μg/kg IBW) are one-third lower than current weight-based dose recommendations for younger populations.     

Combination of BMI and Waist Circumference for Identifying Cardiovascular Risk Factors in Whites

Objective: BMI (kilograms per meters squared) and waist circumference (WC) (measured in centimeters) are each associated with the risk of developing cardiovascular disease (CVD). Therefore, a combination of the two may be more effective in identifying subjects at risk than either alone. The present study sought to identify the combination of BMI and WC that has the strongest association with CVD risk factors in whites. Research Methods and Procedures: Subjects were 8712 white men and women from the Third National Health and Nutrition Examination Survey. The optimal combination of BMI and WC was developed using logistic regression models with BMI and WC as predictors and CVD risk factors as outcomes. The combined measure of BMI and WC using current cut‐off points was also examined. Sensitivity, specificity, and receiver operating characteristics curves were compared between the combined measures and BMI alone. Results: For white men, the optimal combination of BMI and WC for identifying CVD risk factors was 0.68 × BMI + 0.32 × WC. This combination generated a score that better estimated the odds of having CVD risk factors than either alone. For white women, WC alone largely determined the likelihood of having CVD risks. The combination of BMI and WC using current cut‐off points may provide an improved measure of CVD risk. Combined measures showed a higher sensitivity or a shorter distance in receiver operating characteristic curves in the identification of CVD risk factors. Discussion: Combined measures of BMI and WC may provide a higher overall test performance for CVD risk factors and may be useful in some ethnic groups as an improved means of screening subjects for further evaluation in the clinical setting.     

BMI and Health‐Related Quality of Life in Adults 65 Years and Older

Objective: To examine relationships of BMI with health‐related quality of life in adults 65 years and older. Research Methods and Procedures: In 1996, a health survey was mailed to all surviving participants ≥ 65 years old from the Chicago Heart Association Detection Project in Industry Study (1967 to 1973). The response rate was 60%, and the sample included 3981 male and 3099 female respondents. BMI (kilograms per meter squared) was classified into four groups: underweight (<18.5), normal weight (18.5 to 24.9), overweight (25.0 to 29.9), and obese (≥30.0). Main outcome measures were Health Status Questionnaire‐12 scores (ranging from 0 to 100) assessing eight domains: health perception, physical functioning, role limitations‐physical, bodily pain, energy/fatigue, social functioning, role limitations‐mental, and mental health. The higher the score, the better the outcome. Results: With adjustment for age, race, education, smoking, and alcohol intake, obesity was associated with lower health perception and poorer physical and social functioning (women only) but not impaired mental health. Overweight was associated with impaired physical well‐being among women only. Both underweight men and women reported impairment in physical, social, and mental well‐being. For example, multivariable‐adjusted health perception domain scores for women were 50.8 (underweight), 62.7 (normal weight), 60.5 (overweight), and 52.1 (obese), respectively. Associations weakened but remained significant with further adjustment for comorbidities. Discussion: Compared with normal‐weight people, both underweight and obese older adults reported impaired quality of life, particularly worse physical functioning and physical well‐being. These results reinforce the importance of normal body weight in older age.     

Fitness Alters the Associations of BMI and Waist Circumference with Total and Abdominal Fat

Objective: We tested the following hypotheses in black and white men and women: 1) for a given BMI or waist circumference (WC), individuals with moderate cardiorespiratory fitness (CRF) have lower amounts of total fat mass and abdominal subcutaneous and visceral fat compared with individuals with low CRF; and 2) exercise training is associated with significant reductions in total adiposity and abdominal fat independent of changes in BMI or WC. Research Methods and Procedures: The sample included 366 sedentary male (111 blacks and 255 whites) and 462 sedentary female (203 blacks and 259 whites) participants in the HERITAGE Family Study. The relationships between BMI and WC with total fat mass (determined by underwater weighing) and abdominal subcutaneous and visceral fat (determined by computed tomography) were compared in subjects with low (lower 50%) and moderate (upper 50%) CRF. The effects of a 20‐week aerobic exercise training program on changes in these adiposity variables were examined in 86% of the subjects. Results: Individuals with moderate CRF had lower levels of total fat mass and abdominal subcutaneous and visceral fat than individuals with low CRF for a given BMI or WC value. The 20‐week aerobic exercise program was associated with significant reductions in total adiposity and abdominal fat, even after controlling for reductions in BMI and WC. With few exceptions, these observations were true for both men and women and blacks and whites. Discussion: These findings suggest that a reduction in total adiposity and abdominal fat may be a means by which CRF attenuates the health risk attributable to obesity as determined by BMI and WC.     

BMI and Waist Circumference; Cross-Sectional and Prospective Associations with Blood Pressure and Cholesterol in 12-Year-Olds

Objective

Childhood and adolescent overweight, defined by body mass index (BMI) are associated with an increased risk of cardiovascular disease in later life. Abdominal adiposity may be more important in associations with cardiovascular diseases but waist circumference (WC) has been rarely studied in children. We studied associations between BMI and WC and blood pressure (BP) and cholesterol in 12-year-old children and prospectively changes in BMI or WC status between age 8 and 12 years and BP and cholesterol at age 12.

Study Design

Weight, height, WC, BP and cholesterol concentrations were measured in 1432 children at age 12 years. Linear regression was used to study the associations between high BMI and large WC (>90^th percentile) and BP and cholesterol.

Results

Systolic BP was 4.9 mmHg higher (95% (CI 2.5, 7.2) in girls and 4.2 mmHg (95%CI 1.9, 6.5) in boys with a high BMI. Large WC was also associated with higher systolic BP in girls (3.7 mmHg (95%CI 1.3, 6.1)) and boys (3.5 mmHg (95%CI 1.2, 5.8)). Diastolic BP and cholesterol concentrations were significantly positively (HDL cholesterol negatively) associated with high BMI and large WC, too. Normal weight children with a history of overweight did not have higher blood pressure levels or adverse cholesterol concentrations than children that were normal weight at both ages.

Conclusion

A high BMI and large WC were associated with higher BP levels and adverse cholesterol concentrations. WC should be taken into account when examining cardiovascular risk factors in children.     

Cut‐points for Waist Circumference in Europids and South Asians

There is little strong evidence that currently recommended higher waist circumference cut‐points for Europids compared with South Asians are associated with similar risk for type 2 diabetes. This study was designed to provide such evidence. Longitudinal studies over 5 years were conducted among 5,515 Europid and 2,214 ethnically South Asian participants. Age‐standardized diabetes incidence at different levels of waist circumference and incidence difference relative to a reference value were calculated. The Youden Index was used to determine waist circumference cut‐points. At currently recommended cut‐points, estimated annual diabetes incidence for a 50‐year‐old Europid was <0.6% for both sexes, and for a 50‐year‐old South Asian, 5.8% for men and 2.1% for women. Annual diabetes incidence of 1% was observed for a 50 year old at a waist circumference 35–40 cm greater in Europid compared to South Asian men and women. Incidence difference between recommended cut‐points and a reference value (80 cm in men, 70 cm in women) was 0.3 and 4.4% per year for Europid and South Asian men, and 0.2 and 0.8% per year for Europid and South Asian women, respectively. Waist circumference cut‐points chosen using the Youden Index were shown to be dependent on obesity levels in the population. The much higher observed risk of diabetes in South Asians compared to Europids at the respective recommended waist circumference cut‐points suggests that differences between them should be greater. Approaches that use the Youden Index to select waist circumference cut‐points are inappropriate and should not be used for this purpose.