Obesity, Disability, and Movement Onto the Disability Insurance Rolls

Between the early 1980s and 2002, both the prevalence of obesity and the number of beneficiaries of the Social Security Disability Insurance program doubled. We test whether these trends are related; specifically, we test whether obesity causes disability and movement onto the disability rolls. We estimate models of instrumental variables using two nationally representative data sets, the Panel Survey of Income Dynamics and the National Longitudinal Survey of Youth, 1979 Cohort. The results are mixed but we find evidence that weight increases the probability of health-related work limitations and the probability of receiving disability related income. Our results suggest that the failure to treat obesity as endogenous leads to dramatic underestimates of the link between obesity and disability outcomes. Authors’ Acknowledgements We thank seminar participants at Ohio State University and the 2004 Conference of the Social Security Retirement Research Consortium for their helpful comments. We gratefully acknowledge financial support from the University of Michigan Retirement Research Consortium and the Bronfenbrenner Life Course Center at Cornell University. We thank Shuaizhang Feng for expert research assistance.

Beyond BMI: The Value of More Accurate Measures of Fatness and Obesity in Social Science Research

Virtually all social science research related to obesity uses body mass index (BMI), usually calculated using self-reported values of weight and height, or clinical weight classifications based on BMI. Yet there is wide agreement in the medical literature that such measures are seriously flawed because they do not distinguish fat from fat-free mass such as muscle and bone. Here we evaluate more accurate measures of fatness (total body fat, percent body fat, and waist circumference) that have greater theoretical support in the medical literature. We provide conversion formulas based on NHANES data so that researchers can calculate the estimated values of these more accurate measures of fatness using the self-reported weight and height available in many social science datasets. To demonstrate the benefits of these alternative measures of fatness, we show that using them significantly impacts who is classified as obese. For example, when the more accurate measures of fatness are used, the gap in obesity between white and African American men increases substantially, with white men significantly more likely to be obese. In addition, the gap in obesity between African American and white women is cut in half (with African American women still significantly more likely to be obese). As an example of the value of fatness in predicting social science outcomes, we show that while BMI is positively correlated with the probability of employment disability in the PSID, when body mass is divided into its components, fatness is positively correlated with disability while fat-free mass (such as muscle) is negatively correlated with disability.

The Ability of Various Measures of Fatness to Predict Application for Disability Insurance

This paper compares a variety of measures of fatness (e.g. BMI, waist circumference, waist-tohip ratio, percent body fat) in terms of their ability to predict application for Social Security Disability Insurance (DI). This is possible through a recent linkage of the National Health and Nutrition Examination Survey (NHANES) III to Social Security Administration (SSA) administrative records. Our results indicate that the measure of fatness that best predicts application for DI varies by race and gender. For white men, BMI consistently predicts future application for DI. For white women, almost all are consistently predictive. For black men, none predict application. For black women, waist circumference and waist-to-hip ratio are the only significant predictors of DI application. This variation across race and gender suggests that the inclusion of alternative measures of fatness in social science datasets should be considered, and that researchers examining the impact of fatness on social science outcomes should examine the robustness of their findings to alternative measures of fatness.

A New Analysis Method for Reconstructing the Arrival Direction of TeV Gamma-rays Using a Single Imaging Atmospheric Cherenkov Telescope

We present a method of atmospheric Cherenkov imaging which reconstructs the unique arrival direction of TeV gamma rays using a single telescope. The method is derived empirically and utilizes several features of gamma-ray induced air showers which determine, to a precision of 0.12 degrees, the arrival direction of photons, on an event-by-event basis. Data from the Whipple Observatory's 10 m gamma-ray telescope is utilized to test selection methods based on source location. The results compare these selection methods with traditional techniques and three different camera fields of view. The method will be discussed in the context of a search for a gamma-ray signal from a point source located anywhere within the field of view and from regions of extended emission.Comment: 24 pages, 16 figures, accepted for publication in Astroparticle Physics May 11, 200

Numerical simulation of grain size distributions in liquid phase sintered materials

Many technologically important ceramics such as silicon nitride ceramics, alumina substrates and barium titanate electrical capacitors are liquid phase sintered. It is important to understand evolution of microstructural features generated by processes such as grain growth so that these materials may be engineered for their respective applications. Grain growth in liquid phase sintered materials by Ostwald ripening has been modeled extensively by both analytical and numerical techniques. However, all models make simplifying approximations to make the problem tractable and the approximations used in these models make them most accurate at very low solid fractions. A two-dimensional, Monte Carlo simulation technique based on the Potts model that makes no assumptions about solid fraction, grain shapes or diffusion fields around grains has been used to study grain growth in fully wetting, liquid phase sintered systems. The grain size distribution, GSD, was found to vary with solid fraction, becoming broader and more peaked with increasing solid fraction. The skewness was near zero at solid fraction of 0.41 and shifted to larger grain sizes with increasing solid fraction

Rodent Control on Poultry Farms.

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The Importance of Objective Health Measures in Predicting Early Receipt of Social Security Benefits: The Case of Fatness

Theoretical models argue that poor health will contribute to early exit from the labor market and the decision to take early Social Security retirement benefits (Old-Age or OA benefits). However, most empirical estimates of the causal importance of health on the decision to take early OA benefits have been forced to rely on global measures such as self-rated work limitations or self-rated health. We contribute to the empirical literature by using a more objective measure of health, fatness, to predict early receipt of OA benefits. We do so by estimating the causal impact of fatness within an empirical model using the method of instrumental variables, and testing the robustness of our findings using the most common measure of fatness in the social science literature -- body mass index -- with what is a more theoretically appropriate measure of fatness -- total body fat and percent body fat. Overall, our conclusion is that fatness and obesity are strong predictors of early receipt of OA benefits.http://deepblue.lib.umich.edu/bitstream/2027.42/49334/2/wp148.pd

Search for gamma-rays from M31 and other extragalactic objects

Although the existence of fluxes of gamma-rays of energies 10 to the 12th power eV is now established for galactic sources, the detection of such gamma-rays from extragalactic sources has yet to be independently confirmed in any case. The detection and confirmation of such energetic photons is of great astrophysical importance in the study of production mechanisms for cosmic rays, and other high energy processes in extragalactic objects. Observations of m31 are discussed. It is reported as a 10 to the 12th power eV gamma-ray source. Flux limits on a number of other extragalactic objects chosen for study are given

Search for gamma-rays above 400 GeV from Geminga

Observations of Geminga made at the Whipple Observatory using the atmospheric Cherenkov technique during the moonless periods of November 1983 to February 1984 and November 1984 till February 1985 were examined for evidence for the emission of gamma rays with energy in excess of approx 400 GeV. Evidence of either a steady flux or a flux pulsed with a period near 60 seconds were studied. In neither case was any significant effect observed, enabling the establishment 3 of sigma upper limits of 5.5 x 10 to the -11th power photons/sq cm/s and 2.0 x 10 to the -11th power photons/sq cm/s for the steady and pulsed emission respectively. The limit to the pulsed flux is approximately a factor of six below that predicted

Rewarding Subjective Effects of the NMDAR Antagonist Nitrous Oxide (Laughing Gas) Are Moderated by Impulsivity and Depressive Symptoms in Healthy Volunteers

BACKGROUND: Nitrous oxide (N2O) is an anaesthetic gas with both therapeutic and abuse potential. As an NMDAR antagonist, its effects are expected to resemble those of the prototypical NMDAR antagonist, ketamine. Here, we examine the subjective rewarding effects of N2O using measures previously employed in studies of ketamine. We also test for moderation of these effects by bipolar phenotype, depressive symptoms, and impulsivity. METHODS: Healthy volunteers were randomised to either 50% N2O (n=40) or medical air (n=40). Self-reported rewarding (liking and wanting), and alcohol-like effects were assessed pre-, peri- and post-inhalation. RESULTS: Effect sizes for the various rewarding/alcohol-like effects of N2O were generally similar to those reported in studies of moderate-dose ketamine. Impulsivity moderated the subjective reinforcing (liking) effects of inhaled gas, while depressive symptoms moderated motivational (wanting [more]) effects. However, depression and impulsivity had opposite directional influences, such that higher impulsivity was associated with higher N2O-liking, and higher depression, with lower N2O-wanting. CONCLUSIONS: To the extent that static (versus longitudinal) subjective rewarding effects are a reliable indicator of future problematic drug use, our findings suggests that impulsivity and depression may respectively predispose and protect against N2O abuse. Future studies should examine if these moderators are relevant for other NMDAR antagonists, including ketamine, and novel ketamine-like therapeutics and recreational drugs. Similarities between moderate-dose N2O and moderate-dose ketamine in the intensity of certain subjective effects suggest that N2O may, at least partially, substitute for ketamine as a safe and easily-implemented experimental tool for probing reward-related NMDAR function and dysfunction in humans