the “normal” range, whether of moderate degree (overweight) or more marked (obese), have long been associated with increases in a number of important biomedical risk factors such as blood lipids, blood pressure, and blood sugar and have been shown to increase the risk for diabetes and a number of forms of cancer and cardiovascular disease. Over the last 30 years of the twentieth century, the prevalence of overweight tripled among children and adolescents while the prevalence of obesity in adults doubled to reach 33 percent (Ogden et al., 2007). Evidence is accumulating that this steady decades-long increase may have abated, as obesity and overweight rates seem to have flattened over the past decade (Ogden et al., 2006 and 2007; Martin, Schoeni, and Andreski, 2010).
Despite the widespread concern about obesity, some observers note that the adverse impact may be exaggerated in the media. Like many risk factors, the effect of increasing weight seems dose-related, with the greatest effects at extreme levels and only modest effects at low levels, despite the fact that such individuals may be labeled overweight or even obese (Wee et al., 2011). In addition, many of the metabolic risk factors associated with obesity, such as hypercholesterolemia, are now being effectively managed with medications, and the cardiovascular risk profile of today’s overweight and obese individuals may be improving. As Martin, Schoeni, and Andreski (2010) say, “Thus, for a variety of reasons, what it means to be obese may be changing, possibly for the better, over time.” A number of biomedical factors, including reductions in smoking, a plateau in the prevalence of obesity, and mitigation of its adverse effects through management, all point to positive changes in biomedically mediated disability in the future.
EDUCATION AND INCOME
Socioeconomic status (SES) has long been recognized as a major predictor of mortality, health status, and disability. The SES effect appears early in life and persists in a graded fashion so that advantage accrues as one “climbs the SES ladder” (Kawachi, Adler, and Dow, 2010). In most analyses education has been used as a proxy for socioeconomic status, which includes income and social status.
Analyses of the independent effects of education are complicated by the obvious selection effects (education is not randomly distributed) and by the clear confound with income, and studies that have tried to disentangle the two have generally shown that they have independent effects. Thorough analyses by Cutler and Lleras-Muney (2006 and 2010) conclude that the health-education gradient is found both for health behaviors and for health status and suggest that cognitive ability and decision-making patterns explain a large portion of the gradient. The effect of education on delaying the onset of disability is robust, dose-dependent, and pres-