scholarly journals Bias due to Berkson error: issues when using predicted values in place of observed covariates

Biostatistics ◽  
2020 ◽  
Author(s):  
Gregory Haber ◽  
Joshua Sampson ◽  
Barry Graubard
Keyword(s):  
Body Fat ◽  
Outcome Variable ◽  
Percent Body Fat ◽  
Unmeasured Confounding ◽  
Berkson Error ◽  
Health And Nutrition ◽  
Consistency Property ◽  
Predicted Values ◽  
Using Data ◽  
Marginal Inference

Summary Studies often want to test for the association between an unmeasured covariate and an outcome. In the absence of a measurement, the study may substitute values generated from a prediction model. Justification for such methods can be found by noting that, with standard assumptions, this is equivalent to fitting a regression model for an outcome variable when at least one covariate is measured with Berkson error. Under this setting, it is known that consistent or nearly consistent inference can be obtained under many linear and nonlinear outcome models. In this article, we focus on the linear regression outcome model and show that this consistency property does not hold when there is unmeasured confounding in the outcome model, in which case the marginal inference based on a covariate measured with Berkson error differs from the same inference based on observed covariates. Since unmeasured confounding is ubiquitous in applications, this severely limits the practical use of such measurements, and, in particular, the substitution of predicted values for observed covariates. These issues are illustrated using data from the National Health and Nutrition Examination Survey to study the joint association of total percent body fat and body mass index with HbA1c. It is shown that using predicted total percent body fat in place of observed percent body fat yields inferences which often differ significantly, in some cases suggesting opposite relationships among covariates.

Fitness and Fatness: Body Mass Index versus Percent Body Fat

2019 ◽  
Vol 8 (4) ◽  
pp. 131-137
Author(s):  
Jennifer Bunn ◽  
Danielle Eustace ◽  
Taylor Miskech ◽  
John Manor ◽  
Michael Jiroutek
Keyword(s):  
Body Mass Index ◽  
Body Mass ◽  
Body Fat ◽  
The United States ◽  
Normal Weight ◽  
Cardiovascular Fitness ◽  
Percent Body Fat ◽  
Tissue Mass ◽  
Weight Category ◽  
Health And Nutrition

ABSTRACT Background: Body mass index (BMI) is frequently used to evaluate risk of disease, but can be misleading because it does not account for different types of tissue mass (e.g., bone, muscle, fat). The purpose of this study was to classify adults in the United States according to cardiovascular fitness (CVF), BMI, and body fat using the National Health and Nutrition Examination Survey (NHANES) data. Methods: The three most current NHANES datasets (6,648 records) were included. Counts, means, and 95% confidence intervals (CI) determined the distribution of CVF across percent of body fat and BMI categories. Results: According to BMI, approximately 42.3% of participants were classified as either underweight or normal weight, and 24.9% were classified as obese. According to percent of body fat, 13.5% of subjects were classified as lean, while 68.4% of subjects were in the high percent body fat group. In regard to BMI, 9.9% and 6.7% of the overweight and obese populations, respectively, were classified in the highest third of CVF. According to adiposity, 6.6% and 21.0% of the moderate and high percent body fat population fell into the same category, respectively. Conclusion: Two-thirds of the population ranked below the 35th percentile for body fat (high percent body fat), with more of these individuals in the low CVF category than any other. The largest categorization for BMI was the normal-weight category. This supports that BMI may be misleading, and that utilizing percent body fat and CVF may provide a better indication of health.

scholarly journals Schools With Fitter Children Achieve Better Literacy and Numeracy Results: Evidence of a School Cultural Effect

2012 ◽  
Vol 24 (1) ◽  
pp. 45-57 ◽  
Author(s):  
Richard D. Telford ◽  
Ross B. Cunningham ◽  
Rohan M. Telford ◽  
Walter P. Abhayaratna
Keyword(s):  
Physical Activity ◽  
Academic Achievement ◽  
Body Fat ◽  
Dominant Role ◽  
School Level ◽  
Percent Body Fat ◽  
Dual Emission ◽  
School Cultures ◽  
Using Data ◽  
The Individual

Relationships of academic achievement (government tests) with physical fitness (multistage run), physical activity (pedometers) and percent body fat (dual emission X-ray absorptiometry) were examined at both the aggregate school level and the individual child level using data collected from 757 children in 29 elementary schools. Statistical adjustments included gender, grade and socioeconomic status. Between-school relationships of the academic scores with fitness and physical activity were strong and positive, with some evidence of (negative) relationships with percent body fat. The between-child relationships were weaker, and nonexistent with percent body fat. Stronger between-school than between-child relationships favor the argument that variation in school cultures, characterized by concurrent attention to fitness and academic achievement, might play a more dominant role in explaining these relationships than any direct effect of fitness on academic achievement.

Validity of V˙o 2 maxin predicting blood volume: implications for the effect of fitness on aging

2000 ◽  
Vol 279 (3) ◽  
pp. R1068-R1075 ◽  
Author(s):  
Victor A. Convertino ◽  
David A. Ludwig
Keyword(s):  
Body Weight ◽  
Blood Volume ◽  
Body Fat ◽  
Aerobic Fitness ◽  
Multiple Regression Model ◽  
Percent Body Fat ◽  
Full Model ◽  
Positive Direction ◽  
Explained Variance ◽  
Using Data

A multiple regression model was constructed to investigate the premise that blood volume (BV) could be predicted using several anthropometric variables, age, and maximal oxygen uptake (V˙o 2 max). To test this hypothesis, age, calculated body surface area (height/weight composite), percent body fat (hydrostatic weight), and V˙o 2 maxwere regressed on to BV using data obtained from 66 normal healthy men. Results from the evaluation of the full model indicated that the most parsimonious result was obtained when age andV˙o 2 max were regressed on BV expressed per kilogram body weight. The full model accounted for 52% of the total variance in BV per kilogram body weight. Both age andV˙o 2 max were related to BV in the positive direction. Percent body fat contributed <1% to the explained variance in BV when expressed in absolute BV (ml) or as BV per kilogram body weight. When the model was cross validated on 41 new subjects and BV per kilogram body weight was reexpressed as raw BV, the results indicated that the statistical model would be stable under cross validation (e.g., predictive applications) with an accuracy of ± 1,200 ml at 95% confidence. Our results support the hypothesis that BV is an increasing function of aerobic fitness and to a lesser extent the age of the subject. The results may have implication as to a mechanism by which aerobic fitness and activity may be protective against reduced BV associated with aging.

scholarly journals High percent body fat mass predicts lower risk of cardiac events in patients with heart failure: an explanation of the obesity paradox

2021 ◽  
Vol 21 (1) ◽  
Author(s):  
Katsuhiko Ohori ◽  
Toshiyuki Yano ◽  
Satoshi Katano ◽  
Hidemichi Kouzu ◽  
Suguru Honma ◽  
...  
Keyword(s):  
Heart Failure ◽  
Body Fat ◽  
Fat Mass ◽  
Cardiac Event ◽  
Muscle Wasting ◽  
Obesity Paradox ◽  
Percent Body Fat ◽  
Body Fat Mass ◽  
Cardiac Events ◽  
Kaplan Meier

Abstract Background Although high body mass index (BMI) is a risk factor of heart failure (HF), HF patients with a higher BMI had a lower mortality rate than that in HF patients with normal or lower BMI, a phenomenon that has been termed the “obesity paradox”. However, the relationship between body composition, i.e., fat or muscle mass, and clinical outcome in HF remains unclear. Methods We retrospectively analyzed data for 198 consecutive HF patients (76 years of age; males, 49%). Patients who were admitted to our institute for diagnosis and management of HF and received a dual-energy X-ray absorptiometry scan were included regardless of left ventricular ejection fraction (LVEF) categories. Muscle wasting was defined as appendicular skeletal muscle mass index < 7.0 kg/m2 in males and < 5.4 kg/m2 in females. Increased percent body fat mass (increased FM) was defined as percent body fat > 25% in males and > 30% in females. Results The median age of the patients was 76 years (interquartile range [IQR], 67–82 years) and 49% of them were male. The median LVEF was 47% (IQR, 33–63%) and 33% of the patients had heart failure with reduced ejection fraction. Increased FM and muscle wasting were observed in 58 and 67% of the enrolled patients, respectively. During a 180-day follow-up period, 32 patients (16%) had cardiac events defined as cardiac death or readmission by worsening HF or arrhythmia. Kaplan-Meier survival curves showed that patients with increased FM had a lower cardiac event rate than did patients without increased FM (11.4% vs. 22.6%, p = 0.03). Kaplan-Meier curves of cardiac event rates did not differ between patients with and those without muscle wasting (16.5% vs. 15.4%, p = 0.93). In multivariate Cox regression analyses, increased FM was independently associated with lower cardiac event rates (hazard ratio: 0.45, 95% confidence interval: 0.22–0.93) after adjustment for age, sex, diabetes, muscle wasting, and renal function. Conclusions High percent body fat mass is associated with lower risk of short-term cardiac events in HF patients.

scholarly journals Association between Dyslipidemia and Mercury Exposure in Adults

2021 ◽  
Vol 18 (2) ◽  
pp. 775
Author(s):  
Purum Kang ◽  
Hye Young Shin ◽  
Ka Young Kim
Keyword(s):  
Behavioral Interventions ◽  
Dietary Habits ◽  
Subjective Health ◽  
Targeted Prevention ◽  
Adult Males ◽  
Subjective Health Status ◽  
Factors Affecting ◽  
Health And Nutrition ◽  
Metal Levels ◽  
Using Data

Background—Dyslipidemia is one of the prominent risk factors for cardiovascular disease, which is the leading cause of death worldwide. Dyslipidemia has various causes, including metabolic capacity, genetic problems, physical inactivity, and dietary habits. This study aimed to determine the association between dyslipidemia and exposure to heavy metals in adults. Methods—Using data from the seventh Korean National Health and Nutrition Examination Survey (2016–2017), 5345 participants aged ≥20 years who were tested for heavy metal levels were analyzed in this study. Multiple logistic regression was conducted to assess the factors affecting the prevalence of dyslipidemia. Results—The risks of dyslipidemia among all and male participants with mercury (Hg) levels of ≥2.75 μg/L (corresponding to the Korean average level) were 1.273 and 1.699 times higher than in those with levels of <2.75 μg/L, respectively. The factors that significantly affected the dyslipidemia risk were age, household income, body mass index, and subjective health status in both males and females. Conclusions—In adult males, exposure to Hg at higher-than-average levels was positively associated with dyslipidemia. These results provide a basis for targeted prevention strategies for dyslipidemia using lifestyle guidelines for reducing Hg exposure and healthy behavioral interventions.

Discriminant Analysis of Personality and Body-Image Factors of Females Differing in Percent Body Fat

1980 ◽  
Vol 50 (2) ◽  
pp. 547-552
Author(s):  
Michael Young ◽  
T. Gilmour Reeve
Keyword(s):  
Body Image ◽  
Body Fat ◽  
Image Data ◽  
Female College Students ◽  
Percent Body Fat ◽  
Personality Factor ◽  
Personality Factor Questionnaire ◽  
Discriminant Analyses ◽  
Low Levels ◽  
Body Cathexis

The purpose of the study was to determine whether individuals with high percent body fat can be distinguished on the basis of personality and body-image from those possessing lower levels of body fat. 65 female college students were administered the 16 Personality Factor Questionnaire and the Secord and Jourard Body-cathexis Scale. Measurements of height, weight, and skin folds at the triceps and illiac crest were also taken. On the basis of percent body fat two groups of 20 females each (high and low percent body fat) were identified. From discriminant analyses one personality factor and six body-image items were identified which distinguished between groups. Reclassification of the subjects, based upon derived discriminant functions, resulted in 60.0% of the subjects being correctly reclassified from personality data and 100% of the subjects correctly reclassified from body-image data. Body-image appears to be an important factor that can distinguish between individuals possessing high and low levels of body fat.

scholarly journals Later Meal and Sleep Timing Predicts Higher Percent Body Fat

Nutrients ◽  
2020 ◽  
Vol 13 (1) ◽  
pp. 73
Author(s):  
Elizabeth A. Thomas ◽  
Adnin Zaman ◽  
Marc-Andre Cornier ◽  
Victoria A. Catenacci ◽  
Emma J. Tussey ◽  
...  
Keyword(s):  
Body Fat ◽  
Overweight And Obesity ◽  
Percent Body Fat ◽  
P Value ◽  
Activity Monitors ◽  
Food Records ◽  
Sleep Timing ◽  
Meal Timing ◽  
Increased Risk ◽  
Unit Increase

Accumulating evidence suggests that later timing of energy intake (EI) is associated with increased risk of obesity. In this study, 83 individuals with overweight and obesity underwent assessment of a 7-day period of data collection, including measures of body weight and body composition (DXA) and 24-h measures of EI (photographic food records), sleep (actigraphy), and physical activity (PA, activity monitors) for 7 days. Relationships between body mass index (BMI) and percent body fat (DXA) with meal timing, sleep, and PA were examined. For every 1 h later start of eating, there was a 1.25 (95% CI: 0.60, 1.91) unit increase in percent body fat (False Discovery Rate (FDR) adjusted p value = 0.010). For every 1 h later midpoint of the eating window, there was a 1.35 (95% CI: 0.51, 2.19) unit increase in percent body fat (FDR p value = 0.029). For every 1 h increase in the end of the sleep period, there was a 1.64 (95% CI: 0.56, 2.72) unit increase in percent body fat (FDR p value = 0.044). Later meal and sleep timing were also associated with lower PA levels. In summary, later timing of EI and sleep are associated with higher body fat and lower levels of PA in people with overweight and obesity.

Multiple nutritional currencies shape pregnancy in a large herbivore

2020 ◽  
Vol 98 (5) ◽  
pp. 307-315
Author(s):  
J.R. Newby ◽  
N.J. DeCesare
Keyword(s):  
Body Fat ◽  
Fat Body ◽  
Bos Taurus ◽  
Pregnancy Rates ◽  
Deficient Diet ◽  
Large Herbivore ◽  
Using Data ◽  
Reproductive Consequences ◽  
Fat Body Mass

Nutritional condition embodies environmental conditions experienced by animals with survival and reproductive consequences. Body fat is often associated with ungulate fecundity; however, other nutritional currencies may limit fecundity. Using data from 129 moose (Alces alces (Linnaeus, 1758)) monitored over 429 moose-years, we examined the limiting role of multiple nutritional currencies on pregnancy rates while concurrently assessing the influence of age and prior reproduction. Females tended to be pregnant in successive years, suggesting differences in individual or habitat quality. However, probability of pregnancy declined with survival of calves from prior litters, indicating a reproductive cost to rearing offspring. Pregnancy was positively associated with serum iron (Fe), body fat, body mass, and serum protein. The best model predicting pregnancy included serum Fe, body fat, and age class, with serum Fe being the strongest single predictor. Moose with Fe concentrations considered deficient in cattle (Bos taurus Linnaeus, 1758) had pregnancy rates of 33%–35%, whereas 89%–91% of individuals with sufficient Fe were pregnant. We subsequently evaluated hypotheses concerning factors potentially limiting Fe concentrations, including Fe-deficient diet, chronic infection, parasitism, and malnutrition. The best supported hypothesis was energy and protein malnutrition constrained Fe stores. We conclude that subclinical anemia due to nutritional constraints can limit or indicate limits in moose fecundity.

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