Obesity: What It Means For Actuaries
Obesity: What It Means For Actuaries
By Sam Gutterman
Newspapers and science publications seem to have two themes concerning prospects for future life expectancy: (1) potentially far reaching medical and drug advances and rosy prospects in the development of genetics and stem cell research; and (2) actual and possible epidemics of infectious disease, obesity and diabetes. Although most actuaries recognize the significant resulting uncertainty, many, especially those involved in annuities, pensions and social insurance, see most of the mortality/survival risk resulting from a possible underestimation of mortality improvement. The potentially significant biological advances in slowing the aging process itself, as presented at the Living to 100 Symposium held in January 2008, add to this uncertainty.
In the near future, prospects indeed look bright, as evidenced by an overall U.S. age–adjusted population mortality improvement between 2003 and 2004 of 3.8 percent, and according to preliminary 2006 experience there was a 2.8 percent age–adjusted rate of improvement between 2005 and 2006 (although only a 0.2 percent improvement between 2004 and 2005). For both the 2003–04 and 2005–06 periods, the rate of improvement was even greater for those older than age 65.
In contrast, small warning signs regarding longer–term trends were flashing intermittently from several of the speakers at the symposium, including the keynote luncheon speaker, Jay Olshansky, and authors of two papers, Mike Cowell and myself. Mike emphasized the negative effect of certain lifestyle choices both in his paper1 and in his article in the June/July issue of The Actuary, while Jay emphasized a wide range of signals, including what may be a recent adverse change in certain cardiovascular risk factors in the United States that followed a long period of improvement in those factors. My paper emphasized the potentially adverse effect of certain human behaviors that may offset that of medical advances, especially those that contribute to obesity. Not only are the trends themselves sometimes difficult to identify, but because of the long lag time between onset of risk conditions and premature death, the uncertainty associated with their effects can be large.
We have of course seen the huge effect on mortality that cigarette smoking has—as a result of its growth and decline in use over the last century. Due to the very long time lag between smoking and its consequential adverse health outcomes, these effects were difficult to foresee. I remember a series of heated discussions in the mid–1970s I had with several statisticians working for the tobacco industry concerning the difference between consistent correlation and causality. The changes in this behavior are still affecting the absolute and relative rate between the genders of mortality improvement, with the effect of the decrease in smoking by females only now starting to be seen. Such a delay may be affecting the observed effect of the recent increase in obesity as well.
My paper2 (from which much of the following is extracted) focuses on the obesity epidemic of the last 35 years. It really has been an epidemic, because the increase in average weight, particularly of those of greatest weight, has been far greater than anyone would have imagined in 1970.
But what is meant by obesity and why should we care? In some cultures obesity is a sign of being successful, as only those who have enough resources to eat well can attain elevated weight, and in some countries those of higher income have a higher percentage of the population that are obese. Although there are several possible ways of measuring obesity, most use the body mass index (BMI)—weight in kilograms divided by the square of that person's height in meters. For some population segments, such as those older than age 70, one's waist circumference has often been found to be more indicative of poor medical prospects (as fat in the abdomen has generally been found to have more adverse health consequences than fat found elsewhere). A further complication is that weight in some cases can be more indicative of fit muscles than fatness (adiposity), so the BMI may be more useful for analysis of a population rather than predictive of an individual's future mortality.
Nevertheless, the study of BMIs has proven useful. The following table shows BMIs at common height and weight combinations. How do you stack up? The table shows the obese category split into three classes.
In 2005–2006, according to a nationally representative survey3 in the United States, 34.4 percent of adults were obese (as indicated by a BMI of 30 or more), with another one–third of the adult population falling into the overweight category (those with a BMI between 25 and 30). According to this same study, U.S. adult prevalence of all those obese during 2005–2006 by age, gender and selected ethnic group are as shown in the following table.
As can be seen, the level of obesity varies significantly by age, gender and ethnic group. But even more startling than the current level has been its tremendous increase since 1970—it has grown in some categories by a factor of more than three times. Even children and adolescents have not been immune to this increase, as it has been observed that a tripling of the percent of children and adolescents in the obese category has occurred (although the most recent cohort may have seen a leveling off in this rapid ascent). Particularly noticeable has been a huge increase in higher levels of obesity, as the entire weight distribution of those in the United States has shifted to the right.
A significant debate has been raging over the causes of this unanticipated and significant trend. In some cases, the arguments raised and many studies have addressed the relative effect of nutrition and exercise—I prefer to look at their joint effect, feeling that the proximate cause for the individual can arise from either or both. The most common factors blamed for obesity and weight gain over the last 30 or 35 years include:
- Increased use of fast food sold at reasonable prices, full of rich energy–dense food.
- Increases in serving size.
- Decreases in physical activity, because of increased use of screen activities (e.g., the Internet and television), continued increases in driving rather than walking or biking, and a switch to knowledge–driven rather than muscular–driven jobs and leisure activities.
- Increases in snack calories.
- Increases in use of corn fructose, especially in soft drinks, that have occurred at the same time the prevalence of obesity has increased.
- Almost universal long–term failure of ever–present dieting.
In contrast, a great deal of professional disagreement in the literature has arisen regarding what the most important contributors of obesity are and their contribution to mortality experience. Some of the studies have suggested:
- The effect of being fit through exercise can be more important than the effect of a person's weight.
- The effect of obesity on mortality has declined because: (1) the primary effect of obesity is on adverse cardiovascular disease incidence; and (2) the prevalence of and risk of death from this disease has seen a significant recent decline.
- Several significant studies of the relationship between obesity and television watching and corn–fructose use have not conclusively indicated that a cause–and–effect exists.
- Little evidence of an adverse effect on mortality of moderately overweight elderly Americans has been observed. In fact, in some cases being overweight has been shown to be protective, for example, through mitigation of severe effects of falling and osteoporosis.
- Moderate obesity does not appear to result in adverse mortality relative to those of lower weight in African–American females, the ethnic population segment with the greatest proportion of obesity.
- Effective bariatric surgery, although expensive, can result in large weight loss and can eliminate some of the most significant side effects of obesity, including diabetes.
- Several recent studies have shown that those who are classified as overweight, and even those with a low level of obesity, do not experience significant adverse mortality risks.
Obesity can result in the following adverse mortality consequences:
- Type 2 diabetes. The North American Association for the Study of Obesity found that about 90 percent of those with this type of diabetes are either overweight or obese. Its rapid increase in prevalence over the past 30 years has paralleled the increase in obesity.
- Cardiovascular risk factors. Obesity is often indicated as an independent risk factor for cardiovascular disease and is included as part of the metabolic syndrome that constitutes a significant risk factor. Obesity is also a risk factor for coronary heart failure, the only common cardiovascular condition whose incidence is currently increasing.
- Cancers. A recent multiyear multicountry panel who studied the results of hundreds of individual studies found4 that overweight/obesity, lack of proper nutrition and lack of physical activity each were independent risk factors for several types of significant cancers. These include post–menopausal breast, endometrial, esophageal adenocarcinoma, pancreas, colorectal, and kidney cancers. This study concluded that these risks were generally found in both those classified as obese and overweight.
- Kidney and gallbladder diseases. Obesity may result in increased risk of chronic kidney disease that can in turn further increase blood pressure, especially when additional adverse factors are present, such as diabetes or lipid abnormalities. The relationship between overweight and gallstone formation is strong as well.
Since the rate of overall mortality has improved over the past century, the question has to be asked whether the effects of other factors have and possibly will continue to more than offset the effect of the behavioral factors referred to in my paper. The following table shows the results of an attribution5 of the major contributing factors to the rate of mortality improvement in cardiovascular disease between 1980 and 2000. Because a significant contributing factor to diabetes is obesity, the level of cholesterol and blood pressure may not improve as much in the future as during this 20–year period, and the total effect of the recent increase in BMI levels may not yet have been fully felt due to the time lags involved, suggests that future mortality improvement may be at risk.
A great deal of public policy discussion has focused on the significant increase in obesity in children and adolescents. Although this is due to adverse physical and psychological effects on the child and adolescent themselves, the concern has been raised in part because of the likelihood that those, particularly obese adolescents, will remain obese as adults. My personal concern was increased as a result of reading a report on a recent large–scale comprehensive study6 of all school children in Denmark who were followed through to adulthood. Being overweight or obese as an adolescent was shown to be a significant risk factor in mortality in adulthood due to coronary disease.
Most of the above discussion relates to experience in the United States. However, similar trends in increases in weight are occurring all over the rest of the world, although obesity prevalence has started from a lower base–level in most countries and adverse trends have begun later. Some have blamed these trends on the spread of Western style nutrition. In fact, Australia (according to a recent survey conducted through self–assessed weights and heights) reportedly has recently surpassed the United States for the distinction of the greatest percent of adults who are obese; and the Mexicans aren't far behind those of us in the United States.
Most of this discussion has focused on the level and effect on mortality of being overweight or obese. I would be remiss in not mentioning that the level of overweight and obesity may have an even more significant effect on morbidity and health care costs than on mortality.
I believe that those actuaries whose practice is affected by the risks of mortality, survival, morbidity or health care costs (most of us?) should keep abreast of this and related developments. It has the potential of affecting the appropriateness of the assumptions you use. My paper goes into far more detail on this topic. It, along with many other interesting papers, can be downloaded from the SOA Web site in the Monograph section of Publications under the 2008 Living to 100 Symposium at www.soa.org/livingto100monographs.
- Cowell, M.J. 2008. "Health, Wealth and Wisdom—Living Long, Living Well: An Actuary Muses on Longevity." Living to 100 Symposium: Society of Actuaries.
- Gutterman, S. 2008. "Human Behavior: An Impediment to Future Mortality Improvement, a Focus on Obesity and Related Matters." Living to 100 Symposium: Society of Actuaries..
- As reported through the 2005–2006 National Health And Nutrition Examination Survey (NHANES) in which height and weight are measured by health care professionals, in contrast with reported self–assessed values in surveys such as the National Health Interview Survey (NHIS) in which in 2007 reported that 26.7 percent of American adults were obese, that historically has been shown to underestimate the level of obesity..
- World Cancer Research Fund/American Institute for Cancer Research. 2007. "Food, Nutrition, Physical Activity, and the Prevention of Cancer: A Global Perspective." Washington, D.C.: AICR..
- Ford, E.S., Ajani, U.A., Croft, J.B., Critchley, J.A., Labarthe, D.R., Kottke, T.E., Giles, W.H., and Capewell, S. 2007. "Explaining the Decrease in U.S. Deaths from Coronary Disease, 1980–2000." The New England Journal of Medicine 356: 2388–2398..
- Baker, J.L., Olson, L.W., and Sorensen, T.I.A. 2007. "Childhood Body–Mass Index and the Risk of Coronary Disease in Adulthood." The New England Journal of Medicine 357: 2329–2337.